vdi user sizing example

Thin Provisioning for Microsoft Exchange 2007

with EMC CLARiiON Virtual Provisioning

and VMware vSphere 4

A Detailed Review

Abstract

The purpose of this white paper is to profile the performance of Microsoft Exchange 2007 on RAID 5 with EMC®

CLARiiON® Virtual Provisioning™. The white paper proves that the chosen configuration is a suitable fit for

Exchange databases, while also proving that CLARiiON Virtual Provisioning provides efficiency in allocating space

and provisioning storage. The white paper also compares performance both with, and without, VMware vStorage

Thin Provisioning.

April 2010

Thin Provisioning for Microsoft Exchange 2007 with EMC CLARiiON Virtual Provisioning and VMware vSphere 4 A Detailed Review

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Copyright © 2009, 2010 EMC Corporation. All rights reserved.

EMC believes the information in this publication is accurate as of its publication date. The information is subject to change without notice.

THE INFORMATION IN THIS PUBLICATION IS PROVIDED ―AS IS.‖ EMC CORPORATION MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WITH RESPECT TO THE INFORMATION IN THIS PUBLICATION, AND SPECIFICALLY DISCLAIMS IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Use, copying, and distribution of any EMC software described in this publication requires an applicable software license. For the most up-to-date listing of EMC product names, see EMC Corporation Trademarks on EMC.com. All other trademarks used herein are the property of their respective owners.

Part number: H6794.1


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Table of Contents

Executive summary ........................................................................................................................... 4 Introduction ........................................................................................................................................ 7 Technology ...................................................................................................................................... 10 Environment .................................................................................................................................... 11 Design ............................................................................................................................................. 15 Testing methodology and results .................................................................................................... 18 Functionality .................................................................................................................................... 24 Conclusion ....................................................................................................................................... 31 References ...................................................................................................................................... 32


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Executive summary

Overview Thin provisioning is a method of optimizing the efficiency of available space used in storage area networks (SAN). Thin provisioning operates by allocating disk storage space in a flexible manner among multiple users, based on the minimum space required by each consumer at any given time.

In the conventional storage provisioning model, also known as fat or thick provisioning, storage space is allocated beyond current needs, in anticipation of growing needs and increased data complexity. As a result, the utilization rate is low. Large amounts of storage space are paid for but may never be used. In thin provisioning, such problems are minimized while keeping overhead low. Added benefits include reductions in:

Large mailbox deployment costs

Consumption of electrical energy

Hardware floor space requirements

Heat generation compared with traditional networked storage systems1

EMC® CLARiiON’s implementation of thin provisioning is provided by its Virtual

Provisioning™ feature. CLARiiON® Virtual Provisioning enables organizations to

present a virtual amount of capacity to a host, therefore allowing the application to consume space as needed without the disruption of reallocation or reconfiguration. This lowers total cost of ownership (TCO) by reducing initial allocation of storage capacity and simplifies management by reducing the steps required to support growth.

VMware’s implementation of thin provisioning is provided by its vStorage Thin Provisioning product, which is a feature of vSphere 4. It provides the option to create thin provisioned virtual disks when deploying or migrating virtual machines (VMs). VMware vCenter provides management screens and capabilities such as raising alerts, alarms and improved datastore utilization reports, to enable management of overprovisioned datastores. Virtual disk thin provisioning increases the efficiency of storage utilization for virtualization environments by using only the amount of underlying storage resources needed for that virtual disk.

This white paper discusses:

How CLARiiON Virtual Provisioning provides efficiency in allocating space and makes it easier to provision storage

The performance of Exchange 2007 on thin vs. thick provisioned storage

Using thin cloning technologies in combination with EMC Replication Manager

The effects of deploying VMware vStorage Thin Provisioning in combination with CLARiiON Virtual Provisioning

1 http://searchstorage.techtarget.com/sDefinition/0,,sid5_gci1214867,00.html

http://searchstorage.techtarget.com/sDefinition/0,,sid5_gci1214867,00.html


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Business case Organizations, both large and small, need to reduce the cost of managing their storage infrastructure while meeting rigorous service level agreement (SLA) requirements and accommodating explosive storage capacity growth. In addition, several business objectives have drawn increasing focus on:

Reducing the cost of storage administration

Maximizing the utilization of storage assets

Maximizing the utilization of server inventory

Reducing capital expenditures and ongoing costs To address these concerns, the CLARiiON CX4 series has introduced thin LUN technology for FLARE

® release 28.000.5 and later. CLARiiON Virtual Provisioning

works with the array’s metaLUNs and traditional LUNs to provide powerful, cost-effective, flexible solutions. CLARiiON thin LUNs can present more storage to an application than is physically available; as a result, storage managers are freed from the time-consuming administrative work of deciding how to allocate drive capacity. When additional physical storage space is required, disk drives can be added nondisruptively to the central storage pool, therefore reducing the time and effort required to provision additional storage. VMware vSphere reduces IT costs and improves flexibility with server consolidation, for example — lower hardware and operating costs, as well as reduced provisioning time for new servers. VMware vSphere also increases energy efficiency by running fewer servers and dynamically powering down unused servers.

Product solution

In many organizations, RAID 1 or RAID 1/0 fully allocated storage is the configuration of choice for Microsoft Exchange deployments. This choice is a natural fit when average mailbox and database sizes are small and the number of disks required to deliver the I/O needs of the user provides more than enough capacity for the average mailbox size. However, in recent versions of Exchange, there has been a shift towards a much larger mailbox size. When combined with a decreasing user I/O profile, RAID 5 and thin provisioned storage are increasingly being considered as potential options for Exchange database storage. This white paper provides the performance test results of 4,000 very heavy Exchange 2007 users (very heavy defined by Microsoft as 0.48 IOPS) when using CLARiiON thin provisioned LUNs in combination with VMware vSphere virtualization technologies. Both Microsoft Jetstress and Load Generator (LoadGen) were used to validate the performance of Exchange 2007 with this configuration. In addition, Replication Manager was used to take Volume Shadow Copy Service (VSS) replicas of Exchange 2007, using thin clone devices on the CLARiiON array.


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Key results The following list details the key results gathered from this white paper. For more information, refer to the Conclusion section.

The configuration used in this environment (virtually provisioned LUNs on RAID 5) satisfied all recommended performance guidelines as provided by Microsoft. An expected performance overhead was observed with thin LUNs in contrast to fully allocated/thick LUNs, but this overhead was minimal.

CLARiiON Virtual Provisioning was easy to configure, and when consumed capacity exceeded the configured ―% Full Threshold‖ setting, expanding the thin storage pools was a simple procedure to complete.


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Introduction

Purpose The purpose of this white paper is to profile the performance of Microsoft Exchange

2007 on RAID 5 with EMC CLARiiON Virtual Provisioning. The white paper proves that the chosen configuration is a suitable fit for Exchange databases, while also proving that CLARiiON Virtual Provisioning provides efficiency in allocating space and provisioning storage. The white paper also compares performance both with, and without, VMware vStorage Thin Provisioning.

Scope The scope of this white paper is to document the:

Design guidelines used to build this environment

Performance test results

Functionality observations

Audience The white paper is intended for EMC employees, partners, and customers, for

example: IT planners, storage architects, and administrators who are interested in evaluating or designing CLARiiON-based Exchange environments that use thin provisioning.

Objectives The objectives of this white paper are to demonstrate how:

CLARiiON Virtual Provisioning can lead to significant cost savings — even in environments where large Exchange 2007 mailboxes for all users and minimized cost of deployment are key requirements.

Desired performance using CLARiiON thin pool configuration can be achieved while still meeting required user performance needs.

Backup and restore for Exchange 2007 databases can be provided with Replication Manager using thin clones.

Appropriate notification is provided when a thin pool approaches the configurable threshold (via the CLARiiON Virtual Provisioning % Full Threshold setting). Expanding the thin pool is also shown in this white paper.


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Terminology This white paper includes the following terminology.

Term Description

Thin provisioning Thin provisioning is a method of optimizing the efficiency of available space used in storage area networks (SAN). Thin provisioning operates by allocating disk storage space in a flexible manner among multiple users, based on the minimum space required by each consumer at any given time.

Notes

VMware uses the term thin provisioning within vSphere, for example ―thin provisioned virtual disks‖. VMware’s implementation of thin provisioning is its ―vStorage Thin Provisioning‖ product.

EMC’s implementation of thin provisioning is its ―CLARiiON Virtual Provisioning‖ feature.

Thin on thin In the context of this white paper, ―thin on thin‖ refers to instances where both VMware vStorage Thin Provisioning and CLARiiON Virtual Provisioning are in operation.

Thick on thin In the context of this white paper, ―thick on thin‖ refers to instances where VMware vSphere is not performing thin provisioning, but the CLARiiON is.

Thick on thick In the context of this white paper, ―thick on thick‖ refers to instances where neither VMware vSphere, nor the CLARiiON are performing any thin provisioning.

Allocated capacity See ―Consumed capacity‖

Available capacity The amount of actual physical thin pool space that is currently not allocated for thin LUNs.

Consumed capacity

For a thin pool, this is the space currently being used by all thin LUNs in the pool. For a thin LUN, this is the physical space used by the LUN.

Oversubscribed capacity

The amount of user capacity configured for thin LUNs that exceeds the physical capacity in a thin pool.

Subscribed capacity

The total amount of capacity configured for thin LUNs in the pool. This number can be greater than the available user capacity. The user capacity can be expanded by adding drives to the pool.

Thin friendly This term is frequently used for file systems and applications that do not pre-allocate all of the storage space during initialization. This term is also used for file systems that reuse deleted space before consuming additional storage. Both features — reuse of deleted space and not pre-allocating — improve capacity utilization in thin provisioning.


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Thin LUN A logical unit of storage where physical space allocated on the storage system may be less than the user capacity seen by the host server.

Thin pool A group of disk drives used specifically by thin LUNs. There may be zero or more thin pools on a system. Disks may be a member of no more than one thin pool.

% Full Threshold A setting that is established by the user. The system generates an alert when this threshold is exceeded.

% Full The percentage of pool capacity that is currently consumed. It is calculated using the following formula:

% Full = consumed capacity / user capacity

Threshold alert An alert issued when the % Full Threshold setting has been exceeded.

Actual capacity The total amount of physical storage capacity in the thin pool that is available for thin LUNs. This is also referred to as ―usable capacity.‖ It is measured as raw disk capacity minus overhead (RAID overhead and mapping overhead).


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Technology

Overview The following section identifies and briefly describes the technology and components

used in the environment. They are:

EMC CLARiiON CX4-480

EMC CLARiiON Virtual Provisioning

EMC Replication Manager

VMware vSphere

EMC CLARiiON CX4-480

EMC CLARiiON CX4 Model 480 provides high-capacity networked storage that meets the needs of high I/O workloads and large-scale e-mail environments. With the CX4-480 it is possible to scale seamlessly up to 471 TB of storage capacity and consolidate twice the workloads in one array as is possible with other storage providers.

EMC CLARiiON Virtual Provisioning

CLARiiON Virtual Provisioning improves energy efficiency by optimizing utilization rates and deferring the use of additional capacity. Virtual Provisioning simplifies storage management by enabling just-in-time capacity allocation via monitoring, alerts, and reporting. It also enables more efficient capacity planning. This reduces the time and effort required to provision additional storage and avoids the need to provision storage that will not be needed in the near term.

EMC Replication Manager

EMC Replication Manager manages EMC point-in-time replication technologies through a centralized management console. Replication Manager coordinates the entire data replication process—from discovery and configuration to the management of multiple application consistent (VSS) disk-based replicas. It is possible to auto-discover a replication environment and enable streamlined management by scheduling, recording, and cataloging replica information including auto-expiration.

VMware vSphere

VMware vSphere is the industry’s first cloud operating system, transforming data centers into dramatically simplified cloud infrastructure and enabling the next generation of flexible, reliable IT services. Leveraging VMware’s industry-leading technology and experience, VMware vSphere delivers uncompromised control, in the most efficient manner, while fully preserving customer choice.


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Environment

Physical environment

The following diagram depicts the physical architecture of the environment.


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Environment profile

The environment profile is detailed in the following table.

Item Value

Application Exchange 2007

Number of Exchange mailboxes 4,000

Number of Exchange mailbox servers 2

Number of users per Exchange mailbox server 2,000

Number of Exchange storage groups 100 (50 per server)

Number of users per storage group 40

Maximum Exchange database size (after thin pool expansion)

200 GB

Exchange user IOPS 0.48 IOPS (very heavy user)

Exchange mailbox quota (subscribed capacity) 5 GB per user (20 TB total)

Note

Virtual capacity as seen by Exchange servers

Exchange mailbox space initially available (actual capacity)

2.8 GB (11.2 TB total)

Note

Physical capacity actually allocated

Exchange mailbox size initially generated (consumed capacity)

1 GB (4 TB total)

Note

Physical capacity actually used

Number of Raw Device Mapping (RDM) LUNs for databases

Note

The reason for using RDMs is detailed in the Design>VSS copies of Exchange section.

20 (10 for each mailbox server)

Number of RDM LUNs for logs 20 (10 for each mailbox server)

Database RDM LUN size 1.1 TB

Log RDM LUN size 50 GB

Number of storage groups per guest operating system database LUN

5

Number of storage groups per guest operating system log LUN

5


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Hardware The hardware used in the environment is listed below.

Purpose Quantity Configuration

Storage 1 EMC CLARiiON CX4-480

Primary storage

40 x 450 GB, 15k, Fibre Channel (FC) drives

o 30 x production (RAID 5 - thin)

o 8 x production logs (RAID 1 - thick)

o 2 x guest OS boot (RAID 1 - thick)

Replica storage2

10 x 1 TB, 7200 rpm SATA drives

o 10 database clones (RAID 5 – thin)

20 x 450 GB FC (RAID 5 - thin)

o 20 database clones (RAID 5 – thin)

Servers 23 16 core, 128 GB RAM, 4 network interface cards (NICs)

Ethernet 1 3750G, 48 port 1 Gb Ethernet switch

Software The software used in the environment is listed below.

Software Version Purpose

VMware vSphere 4.0 Hypervisor hosting all Windows machines

Microsoft Windows 2008 Enterprise SP2

Operating system for Active Directory as well as the Exchange 2007 servers

VMware vCenter 4.0 Management of VMware vSphere

EMC Navisphere® FLARE

® 29 VMware-aware FLARE code

Microsoft Exchange 2007 SP2 Mailbox servers, Hub/CAS servers

EMC PowerPath®/VE 5.4 Multipathing/fault tolerance for storage

connections on VMWare vSphere servers

EMC Replication Manager 5.2.2 Microsoft VSS-based replicas of Exchange 2007(based on cloning thin to thin)

EMC Solutions Enabler 7.0.1.0 (edit level 956)

Required for Replication Manager

2 Two different clone configurations were used.

3 The second server is for VMware High Availability (VMHA).


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Virtual allocation

The virtual allocation of hardware resources for the VMware vSphere virtual machines is listed below.

Virtual machine role Quantity Configuration

Microsoft Active Directory 1 2 vCPUs, 4 GB RAM, Windows 2008 SP2

Hub/CAS 1 2 vCPUs, 8 GB RAM, Windows 2008 SP2

Mailbox servers 2 4 vCPUs, 16 GB RAM, Windows 2008 SP2

Replication Manager server 1 4 vCPUs, 8 GB RAM, Windows 2008 SP2

Replication Manager mount host

1 4 vCPUs, 8 GB RAM, Windows 2008 SP2


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Design

Overview The following sections provide an overview of the design guidelines followed when

building this environment.

VSS copies of Exchange

This white paper demonstrates the use of Replication Manager in combination with SnapView™ functionality on the CLARiiON CX4-480 array. The original intent was to use VSS replicas on Exchange in conjunction with a primary method of local recovery. Thin clones were used in accordance with best practices for capacity utilization (when using thin LUNs for production). As this environment was fully virtualized through VMware vSphere, the opportunity of using vStorage Thin Provisioning in addition to array-based thin provisioning (thin on thin) was presented. However, it is not possible to take VSS copies of Exchange when virtual disks (VMDK files) are used as they do not provide sufficient detail regarding the back-end storage layout. Therefore, this environment’s configuration required the use of RDMs for all Exchange database and log LUNs. This did not detract from the cost savings that were available during initial deployment.


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Exchange storage group to array LUN relationship

The maximum number of LUNs that can be presented to a vSphere host is 256. If each log and database in this environment was configured with an individual array LUN, there would be 200 LUNs for Exchange data and a further 200 for Exchange clones. All of the LUNs and clones would need to be presented to the vSphere host, either for production use or for clone integrity checking. To remain below the 256 limit, five Exchange storage groups were configured for each log and database LUN pair. The five storage groups were treated as a single backup and restore item by Replication Manager. This environment contained a total of 20 database LUNs, each hosting five Exchange databases. The following image illustrates how each thin LUN was configured as a RDM.

Once presented to the guest operating system, the thin LUN was formatted and mounted as a single drive partition or drive letter, and sub-folders were created for each of the Exchange databases. Note A similar process was completed for the log LUNs. In Replication Manager, the five databases and logs, and their associated storage groups were configured as a single Appset.


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Thin pool design

This white paper details the tests that were conducted for a very heavy user Exchange 2007 deployment. The intent was to:

Satisfy the I/O needs of 4,000 very heavy Exchange users, where every user was given a 5 GB mailbox quota

Minimize the initial costs of storage deployment using CLARiiON Virtual Provisioning

By using thin storage, the LUN sizes created and presented to the virtual machines running Exchange look and feel big enough to satisfy the end result of 5 GB per user. In this case, this meant that the guest operating system on the mailbox servers saw database LUN sizes of 1.1 TB (and each database LUN housed five Exchange databases). However, the capacity of the thin pool actually only allows 2.8 GB per user without the provision of additional disks.

Disk spindle calculation

The number of disks required to provide the desired user performance was calculated using the formula shown below. Adding extra spindles at a later time, when the thin pool requires expansion, would also add further IOPS capability to the environment.

(User IOPS x Read Ratio) + Write Penalty (User IOPS x Write Ratio) IOPS capability of disk type chosen

(1920 x 0.5) + 4 (1920 x 0.5) 180

= 27 disks

Recommended RAID 5 configurations

Recommended RAID 5 configurations for thin pools are configured in multiples of 5 disks, so the 27 disks calculated for storage provision were rounded up to 30 disks.

Microsoft’s recommendation is to maintain Exchange database sizes of 200 GB or less. For this environment, it meant a maximum of 40 users per Exchange database (at 5 GB per user). This layout required a maximum of 2,000 users per Exchange mailbox server when using the maximum of 50 Exchange storage groups.

The 30 disks required for performance were split into two thin pools of 15 disks each. This was done to ensure that the performance of one Exchange server (during normal operation, backup, or online maintenance) would not impact the performance of another Exchange server. There is no technical limitation preventing the use of a single thin pool.

Log LUN configuration

Exchange log performance is critical to the overall performance of the Exchange server and the end-user experience. In relation to the size of the database LUNs, the log LUNs are not required to be exceptionally large — assuming regular backups are conducted. Therefore, there is no huge advantage to creating thin log LUNs, as the potential space savings are relatively small. For this reason, the log LUNs were configured in the traditional fashion, that is, thick, fully allocated RAID 1/O devices. A total of eight disks were used to provision the log LUNs in this environment.


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Testing methodology and results

Overview Two testing tools were used to validate the performance of Exchange on the

CLARiiON’s virtually provisioned LUNs. They are listed in the following table.

Tool Description

Microsoft Exchange Jetstress

Used to validate that the storage layout could adequately sustain the IOPS required by the 4,000 very heavy users.

Microsoft Exchange Load Generator (LoadGen)

Used to test the full Exchange environment and to ensure that remote procedure call (RPC) Average Latency and other important counters were acceptable.

Types of test Three types of Jetstress tests were run on the environment. They are listed in the

following table.

Test Test name Description

1 Thick on thin Jetstress testing using RDM devices on thin LUNs for Replication Manager VSS support.

2 Thin on thin Jetstress testing using thin provisioned vSphere virtual disks on thin LUNs (thin on thin) for performance comparison (should VSS disk-based replicas of Exchange not be applicable to the environment).

3 Thick on thick Jetstress testing using RDM devices on traditional thick LUNs to assess the impact of using array-based thin provisioning.

To ensure a fair comparison, Tests 2 and 3 were executed using the same number and type of disks as Test 1.


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Performance test results

This section details the performance test results for Test 1. The results of Tests 2 and 3 are also detailed, including comparisons to Test 1.

Test 1 (thick on thin) results

The configuration for Test 1 passed all Jetstress test runs. The following table details the combined results of both Exchange Servers.

Counter Target value Achieved value

Achieved I/O per second 1,920 2,014

Average database disk sec/read

20 ms or less 15 ms

Average database disk sec/write

20 ms or less 4 ms

Average log disk sec/write

10 ms or less 1 ms

The following chart shows that the array IOPS captured from the Navisphere logs approached 2,900 (1,450 per storage processor).


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The following chart shows that the array IOPS were spread evenly across four iSCSI ports on the CLARiiON (two on each storage processor).

Jetstress initialization metrics

It is important to note that Jetstress populates the data first, and then runs tests against the pre-created data. Because of this, back-end storage has already been allocated to a significant portion of the data being utilized during the test run. This makes it harder to capture the performance impact to the Exchange application when the thin LUNs in question are allocated new chunks of storage from the thin storage pool. To get an impression of the thin LUNs’ performance when allocating storage, separate metrics for the Jetstress initialization phase were captured. During Jetstress initialization, a single database is created and duplicated to the other locations. As a result, for the first 25 - 30 minutes of generation, a period of extremely intensive write activity was visible when the first database was being created. Although this is not a flawless measurement (a near 100 percent write Exchange database is not realistic), it does go some way to help understand how the thin LUN performs when it is continuously asked to allocate storage for new writes. As shown in the following chart, during this period, the average database write response time was 17 ms, which was a significantly higher response time than that seen during the Jetstress test runs.


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On initial analysis this result may look serious, but when comparing the Jetstress database initialization metrics across all storage configurations it becomes clear that the significant increase in write response time can be attributed to the 100 percent write profile of this test, and not because of the thin provisioned LUNs. The following table indicates the average database disk sec/write.

Counter Thick on thin Thin on thin Thick on thick


17 ms 19 ms 17 ms

As expected, thin on thin did add some extra overhead, but all of the configurations stayed within the 20 ms threshold, despite the excessively write-intensive load. Thick on thin showed no difference to thick on thick. The pattern over the 25-minute Jetstress database generation time is depicted in the following chart.


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Comparing the results of Tests 1, 2, and 3

While the Jetstress results of Test 1 (thick on thin) were chosen to provide support for the VSS replicas of Exchange using Replication Manager, the following table compares the results of Test 1 with Test 2 (thin on thin) and Test 3 (thick on thick). Note Thin on thin does not provide support for VSS disk-based replicas of Exchange.

Counter Test 1

(thick on thin)

Test 2

(thin on thin)

Test 3

(thick on thick)

Achieved I/O per second

1,007* 1,009* 1,421*


15 ms 15 ms 11 ms


4 ms 4 ms 4 ms

Average log disk sec/write

1 ms 1 ms 1 ms

*Corresponds to the results for a single 2,000 user Exchange server where expected IOPS was 960. In this configuration, very little difference was observed in the write response times between thick on thick vs. thick on thin. Traditional thick on thick devices did provide some additional read performance and achieved higher IOPS when using the same spindle count. However, the LUNs created using this method needed to be smaller, since the same number and type of disks as Test 1 were used, and overallocation is not permitted with thick devices. It should be noted that extra disks would be required if LUNs with the same subscribed capacity as Test 1 were to be created in a thick configuration.


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Microsoft Exchange LoadGen performance

Microsoft Exchange LoadGen was configured to run for 10 hours using the very heavy user profile. Afterwards, the LoadGen report issued a Succeeded status, as shown in the following image. Note This test was conducted using only the thick on thin configuration (the same disk layout as Test 1 was used). Thin on thin configuration was not tested due to the VSS support limitations referenced in the Design > VSS copies of Exchange section of this white paper.

Other important counters were gathered and are shown in the following table.

Counter Target value Achieved value

RPC Average Latency 50 ms or less 3.6 ms


20 ms or less 8 ms


20 ms or less 6 ms

Average log disk cec/write

10 ms or less 1 ms


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Functionality

Overview The following section details the functionality of Replication Manager during the provisioning of storage. It also details the CLARiiON %Full Threshold setting and the procedure of adding disks to thin pools.

Replication Manager cloning options

Replication Manager discovers any LUNs in the CLARiiON storage group that are named "EMC Replication Storage". Once discovered, Replication Manager is capable of detecting the type of volume being used to clone, and will recommend the two most efficient cloning options, which are:

Thin to thin

Thick to thick The following image shows Replication Manager's view of the LUNs present in the ―EMC Replication Storage‖ CLARiiON storage group. In this environment, they are currently ―In Use‖, which means that they contain a valid replica of Exchange.

Twenty application sets were configured in Replication Manager (10 per Exchange mailbox server) with each application set incorporating the five Exchange storage groups that shared a log or database LUN pairing. The following image shows the 20 application sets that were configured.


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Cloning performance configurations

While mailbox quotas were set at 5 GB, and the storage in the thin pool allowed for 2.8 GB of mailbox data per user (before expansion was required), the initial LoadGen databases were generated to create approximately 1 GB of mailbox data per user. Therefore, it was possible to create thin clones that were even thinner than the thin production LUNs. Two disk configurations were tested for cloning performance:

10 x 1 TB SATA drives were configured as a global thin pool for all clones

20 x 450 GB FC drives were configured as a global thin pool for all clones

Cloning performance results

In both cases, the thin LUNs for the production and clone LUNs were 1.1 TB in size, and it took approximately six hours for initial synchronization of each database LUN, regardless of the underlying disk configuration of the clones.

Clone disk speed and type did not have an effect on timing. This was because during the initial synchronization the array must check the tracks for the entire size of the thin LUN, rather than the consumed capacity. However, since there was no data to copy for a large part of these LUNs, there was no resulting disk activity making clone disk speed non-critical.

Note This behavior will be optimized in future CLARiiON code releases.

Once the initial synchronizations completed, synchronization speeds reverted to that expected by the individual disk type. The length of time to complete all of the synchronizations depends on the quantity of data changed since the last synchronization. However, since thin LUNs are used primarily in overallocated situations with large LUN sizes, it is advisable to configure the clones in advance of writing any data to the production LUNs. This makes it possible to create the clones using the ―No initial-sync required‖ option and only used tracks would be copied in subsequent synchronizations.


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Thin pool % Full Threshold setting

In this environment, the thin pool %Full Threshold setting was configured at 65 percent, meaning that once thin pool usage (consumed capacity) reached 65 percent of actual capacity, the configured notifications would be triggered. Notifications can be viewed in the Navisphere Management user interface. Alternatively, the alerts can be configured to be sent via SNMP or e-mail — providing the storage administrator with immediate visibility. The thin pool for the clone LUNs was deliberately configured to be as space efficient as possible (only 10 percent greater than the consumed capacity of the mailbox servers after initial mailbox data population). This was done to artificially trigger and observe the % Full Threshold setting as soon as the clones were taken off all of the Exchange storage groups. Replication Manager was used to take clones of all the Exchange storage groups. Subsequently, when logging in to the Navisphere Management user interface, an alert was presented to the Administrator, as shown in the following image.


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Expanding a thin pool

The following table details the procedure for expanding a thin pool.

Step Action

1 From within Navisphere, select the appropriate thin pool. Right-click the thin pool and select Expand from the menu option, as shown in the following image.

2 The Expand Thin Pool dialog box will open. From the number of disks to expand by: drop-down list, select the number of drives you

want to expand the thin pool by, as shown in the following image.

Note

Navisphere will automatically provide recommended configurations (multiples of 5 for RAID 5 and multiples of 8 for RAID 6).


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3 Select the drives (manually, or automatically by Navisphere). Click the OK button to complete.

4 The revised thin pool capacity will be updated, as shown in the following image.

Note

The above steps are nondisruptive to any system(s) using the modified thin pool.


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Viewing capacity when using thin provisioned LUNs

The following table illustrates the various views of capacity as seen by the different components of the system (immediately after the guest operating system has formatted and mounted the storage that is presented to it). Note As the target system (in this case, the guest operating system hosting the Exchange mailbox server) always sees the subscribed capacity, it is vital to format the storage at the guest operating system level using a quick format option. If a full format is done at the guest operating system level, it will result in a full allocation at the array level, which will cause the benefits of thin provisioning to be lost.

Component View of capacity

Guest operating system At all times, when using thin provisioned LUNs, the guest operating system sees the subscribed capacity of the LUN, as shown in the following image.

Array The array will always show the true consumed capacity, as shown in the following image.

Virtual machine file system (VMFS) and virtual disk

If VMFS and virtual disk thin provisioning are being used at a vSphere level (as was done for some of the extra Jetstress tests in this environment), then it is also possible to view capacity in vSphere when browsing the relevant datastore. This is shown in the following image.

Virtualization-aware If an environment is using FLARE 29 with the virtualization-aware functionality, the actual capacity consumed by data in the virtual machine can be viewed using the Navisphere user interface. The following image shows capacity when looking at a single thin LUN.


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It is also possible to view capacity when looking at the entire list of LUNs presented to a virtual machine, as shown in the following image.


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Conclusion

Summary This environment successfully demonstrated a design intended for a VMware

vSphere virtualized workload of 4,000 very heavy Exchange 2007 users, where each user was given a 5 GB mailbox quota. The goal was to satisfy the I/O needs of each Exchange user, while minimizing the initial costs of storage deployment using CLARiiON Virtual Provisioning. As expected, there was some overhead associated with the thin provisioned devices in contrast to the thick provisioned devices. At the levels tested in this environment, the overhead was negligible. However, if the intent is to deploy at larger scales, then due diligence should be carried out to ensure adequate performance.

Findings The following list details the findings of this white paper:

CLARiiON Virtual Provisioning can lead to significant cost savings at initial deployment, particularly when the ultimate intention is to provide large Exchange 2007 mailboxes for all users with minimized cost of deployment. Consider the following table when assessing initial disk costs.

Environment Thick provisioned storage

Thin provisioned storage

Initial disk costs

Exchange database LUNs

55 disks (RAID 5)

30 disks (RAID 5) Thin costs are 45 percent lower

100 disks (RAID 1/0) As above Thin costs are 70 percent lower

Desired performance was obtained by basing the configuration of the CLARiiON thin pool on known user performance needs. The environment passed all applicable Microsoft Jetstress and Microsoft LoadGen tests.

VSS replicas of Exchange 2007 databases and logs were successfully taken and restored via Replication Manager using thin clones.

The CLARiiON Virtual Provisioning % Full Threshold setting was demonstrated in the environment. Appropriate notification was provided when a thin pool approached the configured threshold, and the thin pool was subsequently expanded quickly and easily.


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References

White papers For additional information, refer to the following white papers:

EMC CLARiiON Virtual Provisioning – Applied Technology (available on EMC Powerlink

®)

What Is New in VMware vSphere™ 4: Storage – White Paper

http://www.vmware.com/files/pdf/Storage-with-VMware-vSphere.pdf