information week 2011-06 high availability

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Small and midsize enterprises need to build an always-on infrastructure to keep critical systems running.Here’s how to get started. By Randy George >>

June 2011

Plus

Avoid Direct-Attached Storage Temptation >>



Each year, InformationWeek Analytics con-ducts dozens of surveys, most of which con-tain a number of questions we’ve asked foryears so that we can find trends in the re-sponses. One question that always interestsme is how much storage is direct- attachedversus NAS versus SAN. Even in our recent2011 State of Enterprise Storage Survey , 39%of respondents said that 25% or more of theirstorage resources are direct-attached. For allbut the smallest IT shops, direct- attached stor-age is a problem just waiting to happen. In

fact, unless you’re pretty new to IT, it’s proba-bly already been a problem for you.

It doesn’t take too many 3 a.m. nights sittingin a server room with a pile of CDs and tapes,trying to rebuild a server before work startsthe next morning, to have you longing for abetter way. And even if you haven’t had a dis-aster, data almost always lives longer than atypical server does, so decoupling data stor-age from servers makes good sense.

Until recently, server makers weren’t muchhelp in encouraging centralized storage.Servers with more memory capacity and CPUs

were physically bigger, too—with lots of empty drive bays tempting you to load themup with comparatively cheap storage. Therewas no altruistic intent on the part of manu-facturers. Profit margins on 1U and 2U serversare razor thin, so one way for them to gin upsome extra dough has been to add sheetmetal, and power and cooling capacity.

Because it’s easy to fill those empty drivebays, the cheapest way for buyers to add stor-age to their networks is to add the direct-attached variety. It’s also the hardest storage to

manage, the least resistant to failure, and thetoughest to fix when a failure does occur. Tomany IT pros, centralized storage seems evenmore dangerous: There sits one box with oneset of disks that represents a whole lot of eggsin one basket. But good networked storage sys-tems are always built with an N+1 philosophy,with more controllers, fans, power supplies, anddrives than would be minimally needed. Evenpower connects can be redundant so that a

SAN or NAS box isn’t sitting on just one breaker.While it probably doesn’t take much convinc-ing to get you to think about centralizing stor-

age for data, it’s a bigger leapboot images and virtual machparatively expensive centraleaving local disk completely or keeping it around just fotemporary storage. Whicheverto go, it makes a lot of sense (gold masters of system and Vwhere besides on the server i

When it comes to storage, tenterprises have gone too facan do more with less” phil

still working to minimize youspend for storage, re-evaluaview. You’ll save time and resbetter service, and have a moteam with a better, planned, age approach.

Art Wittmann is director of a portfolio of decision-suppoYou can write to him at awitt

More than 100 major rep year. You can sign up or upanalytics.informationweek.co

Avoid The Direct-Attached Storage Trap ART

practical

Analysis


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Strategy for high availability >>

Direct-attached storage trap >>

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On The Road To High AvailaMaking the call about which apps need high availability is a business decisio

Then it’s IT’s job to keep the roads open.

et’s face facts: Servers die, storage fails,network connectivity drops, powergoes out. There are simply too many

things that can go wrong when providing ITservices, even for a simple application. At thesame time, small and midsize enterprises won’t

tolerate outages. Thus, it’s incumbent upon ITto build for high availability. You need multipleroads in your network, storage, and application

layers to ensure employees can access the in-formation and apps they need.

High availability (HA) means building redun-dancy into critical business systems so the fail-ure of one component, such as a bad NIC in aserver, won’t cause the application to fail. It’s

similar to building multiple highways into acity: If problems arise on one road, traffic cantake an alternate route. Standard HA practices

include deploying redundanusing multiple network links.

The decision to build hightems, however, should alwaydecision. That’s because HA iworking with the business uni

on the services that are trucompany. With a clear mandcan formulate a cost-effectiv

By Randy George

L

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Get This AndAll Our ReportsBecome an InformationWeek Analytics subscriber and get ourfull back up report.

This report includes 35 pages of action-oriented analysis, packedwith 25 charts.

What you’ll find:

> Insight on backup, deduplica-tion, and cloud-based storage

> Discussion of virtualization andbackups

> Survey results from 420 IT pros

DownloadDownload



the pressure is on IT to pick the right technolo-gies to get the job done.

Measure FirstBefore you start building multiple roads, you

have to know the amount of traffic to accom-modate. In other words, don’t build a six-lanehighway if you only need two. Every applica-tion consumes memory, processing, network capacity, and storage in a unique way. As a re-sult, the first part of the process is to assess theresources your core applications need to runproperly. Your application and workload analy-sis will naturally unearth the degree of avail-ability you need to get the job done, and yourdesign will flow from there.

That’s the technical side. You also need towork with the business side to calculate howmuch the downtime of critical applicationscosts the company—which in turn will dictatehow much you can spend to keep systems upand running. For instance, do seconds or mil-liseconds matter on a transaction-by-transac-tion basis? Such calculations will determinewhether you need to build a two-, four, or six-lane highway.

Let’s use Microsoft Exchange as an example.Business has very little patience for email be-ing down, so spending the dollars to bring

[COVER STORY]HIGH AVAILABILITY

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more availability to your messaging environ-ment is the answer. To assess your applicationrequirements, look at factors like CPU utiliza-tion and the kinds of messaging load you sup-port; for instance, your users may send highvolumes of email with large files attached. These data points will influence your serverand storage designs.

Let’s say you run Exchange 2007 and sup-port 500 users with medium to heavy work-loads. Your back-end mail server is averag-ing 10% CPU utilization on an eight-coreserver. You also have a separate set of virtu-alized servers that average 35% CPU utiliza-tion. In this scenario, you can safely add avirtualized instance of Exchange to act as a

redundant cluster node without affectingexisting services.

Once your analysis is complete, you can begin laying the foundations for high avail-ability in your network, storage, and ap -plication infrastructures.

Network ResiliencyNo matter what your application, whether

it’s messaging, a point-of-sale system, or acomplex business analytics package, addingnetwork resiliency makes sense because the

network is where you’re likfailures.

Step one to building netwto take advantage of capabuilt into your gear. Assum

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Data: InformationWeek Analytics 2010 State of Server Technology Survey of 579 business technology professionals, F

Hold server couservers on our n

Increase both thand capability o

26%

Increasewith sim

Attempt to freeze overall server purchasing;extending the life of the servers we have

Decrease overall count; we need fewer servers

19%

6%

2%5%

42%

Decrease overall count;consolidating old servers to

fewer new, more capable systems

26

1

6

2%

What’s Your Server Purchase Or Upgrade Plan For 2010-2



ning enterprise-class routers and switches,you already have access to some of the fea-tures needed to do the job. For instance,many routers support protocols that providebasic redundancy. Key protocols to use in-clude Hot Standby Router Protocol and Vir-tual Routing Redundancy Protocol, both of which allow a secondary router to take overif the primary fails, ensuring that traffic con-tinues to flow.

The next step is to extend that redundancythroughout the different tiers of your net-work. For example, do you have critical appli-cations that need to be accessible from out-side your network? If so, you may need to addredundant firewalls and routers along your

path to the Internet. For customer-facing busi-ness applications, consider adding a secondInternet link from your provider. And sinceyou’re accounting for all variables, look intousing more than one carrier.

Don’t forget the critical servers connectedto your network. The shift to highly virtual-ized environments has prompted all the major server vendors to add multiple-gigabitEthernet NICs to their system boards. Thismeans you can take advantage of NIC team-ing, in which multiple interface cards appearas a single interface to the virtual machines

on a server. If one physical NIC fails, trafficstill passes to the virtual machines. NICteaming extends HA right down to theserver level.

Storage’s ChallengesNetwork issues are comparatively easy to fix,

but storage issues are not, which makes a fullyredundant storage design imperative for crit-ical applications. And don’t just point to youruse of RAID and call it a day. RAID is great fordata protection, but it won’t cut it as a com-prehensive clustered storage strategy.

The process and ultimate cost to imple-ment storage HA depends greatly on thestorage transport you select, the capabilities

of your storage platform, your I/O require-ments, and to some degree the capabilitiesof your network.

Fibre Channel is a popular storage network technology and many companies have in-vested in it. If this includes you, at the veryleast you should add redundant host busadapters (HBAs) to critical servers, and thoseservers should be collapsing back to redun-dant Fibre Channel switches.

However, Fibre Channel is expensive, and it’soften overkill for many small and midsizecompanies. A sound alternative is iSCSI, which

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Network High Avail

To ensure availability, build reduntier in the network, including at gfirewalls, network core and edge sand in server NICs.

LAN

Routinglayer

Firewal

Internet

Networkcore

Edgelayer

Servers wmultiple

NICs



is widely deployed and very stable whenproperly implemented.

From a performance perspective, logicwould indicate that 4-Gbps Fiber Channel isfour times as fast as 1-Gbps iSCSI. However, ac-cording to benchmarks run by EnterpriseStrategy Group, a software-based 1-GbpsiSCSI target can pump through approximately80% to 85% of the throughput and input/out-put operations per second of a 4-Gbps FibreChannel HBA. Given that many enterprise-class servers have four 1-Gbps NICs on board,you essentially get 85% of what Fiber Channelis giving you for free, because any Gigabit Eth-ernet NIC can be turned into an iSCSI adaptor.

As a result, budget-strapped IT managers

who need to build solid storage HA can do somuch more cheaply with iSCSI. You don’t nec-essarily need a name-brand SAN, either.Smaller shops can easily build a starter iSCSISAN using a server with direct-attached stor-age: All you need is software to spin that DASstorage into iSCSI. FreeNAS is one open sourceoption you can use to turn DAS into an iSCSItarget, and there are others.

Another option is Fibre Channel over Ethernet(FCoE), which lets IT shops use their existingEthernet network for storage transport, insteadof having to build out a Fibre Channel storage

network with its specialized (and expensive)switches, HBAs, and cabling. The increasing pen-etration of 10-GbpsEthernet makes FCoE a par-ticularly viable alternative, and having a con-verged data and storage network also reducesmanagement complexity and costs. (For more

on FCoE, see our Informatiosearch report on Ethernet conv

Regardless of your storagsider storage replication bestorage chassis. Discussionscation inevitably lead to talk ery and business continuityyond the scope of this articessential that you calculate thtime of business-critical appdown will cost you hundredsdollars in a given time periodextend your availability and bilities to a disaster recoveryLayer 2 connectivity. If youurban area, there’s a good c

tion facility is close by, and yfrom a provider that will gibandwidth for your disaster r

Application ClusteringIn addition to building ava

network and storage systemapplication infrastructure. Thmethod for increasing applicis by building a cluster. A clusware and software componenware side, you can add multone component in a server

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Fibre Channel High Availability

Critical business applications need reliable storage.In a Fibre Channel environment, that meansredundant FC switches, as well as redundant hostbus adapters in servers. Replication of data storageamong SANs is also recommended.

Fibre Channelswitches

Servers with FibreChannel HBAs

SAN replication

LAN

SAN SAN



other component in the cluster takes up theslack. Virtualization will also come into play inyour server cluster: Running an application in-side a VM can make it easier to restore the op-erating system and application if necessary.You can also take advantage of live migration,which can move VMs to different physicalservers. This feature comes in handy if you de-tect conditions that indicate a server is aboutto go down.

The hard part of building a cluster oftencomes in integrating all the software compo-nents that make up a complex, multitiered ap-plication. Broadly speaking, for an applicationto be “cluster aware” it must be able to syn-chronize state information between nodes, so

existing sessions can dynamically fail over toanother node in the cluster.

Consider our earlier messaging example.Windows Server supports a few HA scenariosfor building a fully clustered Exchange envi-ronment through the use of failover clusteringservices. In Windows 2008 Server, it can simplybe added as a server feature (not a role).Failover clustering works by listening for heart-beats (effectively, a ping response) from all thenodes in the cluster over a dedicated Layer 2link. If the heartbeat is no longer detected onthe primary node, all Outlook client connec-

tions are transferred over to a passive node.Clustering a multitiered application is a

whole different ball of wax. Most scalable ap-

plications have a Web access layer (such as IIS,Apache, or Tomcat), a middleware layer toprocess core business logic (WebSphere Ap-plication Server or the like), and a back-enddatabase. The challenge now becomes mak-ing each layer cluster-aware.

The Web Challenge The Web access layer presents unique chal-

lenges. For example, say you’re running a Webapplication using IIS. From a clustering per-spective, when should a Web application failover to a passive node? When the IIS service

fails completely? When a Tlonger be established on thWhen you start detecting HT

Server Error) or HTTP 503able) errors?

Unfortunately, using Microtering for IIS isn’t particularlviding HA for your Web mended fallback for crearesiliency in IIS is to use the Load Balancing feature. Honot synchronize session stateserver is lost at any point insion state data on the failed n

Therefore, it’s common toload balancer (hardware or s

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How Much Of Your Storage Uses These Technologies For C

Data: InformationWeek Analytics 2011 State of Enterprise Storage Survey of 377 business technology professionals, Nov

None

7%

17%

14%

14%

13%31%

27%

17%

7%

23%

24%

8%

35% 11%

9%65%

17% 13%

7%

9%

10%

15%

8

1% to 9% 10% to 24% 25% to 49% 50% to 74% 75% to 99% 100% Don’t kno

Direct-attached storage

Network file system (NFS, CIFS)

Fibre Channel SAN

iSCSI SAN

Fibre Channel over Ethernet SAN



of your Web server farm. The load balancermakes dynamic decisions about the healthand capacity levels of the Web servers it sitsin front of. F5 is the market leader in load bal-ancing and application delivery controllers(ADCs). Cisco Systems and Citrix are also major players in this market.

An ADC will serve you well at the Web ac-cess layer, but you also need to cluster themiddleware layer. It doesn’t do you any goodto have an ADC in front of multiple Webservers if they are all collapsing back to a sin-gle application server. Major applicationservers, such as IBM WebSphere, Oracle Appli-cation Server, and Sun App Server, include in-ternal clustering capabilities.

At the database level, if you’re using Mi-crosoft SQL, you can use Microsoft ClusterService to build a multinode shared storageSQL cluster. MSCS (known as failover cluster-ing in Windows Server 2008 R2) providesfailover capabilities built directly in the Win-dows operating system.

In Oracle land, Oracle Fail Safe can be usedin conjunction with MSCS as a software-basedHA tool for Oracle databases running on Win-dows boxes.

Another option is to use a third-party proxyto add load balancing and failover capabilities

for your databases. For example, Citrix’s

NetScaler DataStream can proxy SQL transac-tions between the client and server and routedatabase I/O in a similar fashion to the wayWeb server traffic is distributed among nodesin a cluster.

A benefit of using a proxy is that read andwrite SQL statements can be intelligently is-sued to the back-end database to increase ef-ficiency, which gives you an immediate scala-bility boost to your database servers.

In today’s always-on businesses, HA isn’t aluxury. The failure of critical IT systems canhave direct costs to the business, from re-

duced user productivity to l

revenue and goodwill. Therbent on both IT and businessand midsize enterprises to mfor core applications.

By targeting key network,plication layers, and by takiboth built-in device capabiparty products, IT can mamore resilient to the inevitaoccur in any technology syst

Randy George is a network e Analytics contributor. Write to

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Data: InformationWeek Analytics 2010 State of Server Technology Survey of 579 business technology professionals, Fe

54%

Choose the serverplatform that bestfits the application

No preferred method

Different vendors,according to the best deal

Singlelevera

(incluknowl

18%

25%

3%

54

8%

25%

How Do You Approach Buying Servers?




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