Block level sharing of storage in microservers using Lightpeak technology

Introduction

• Microservers are essentially servers that pack a lot of processors and storage in to their chassis.

• Sharing of data in microservers is done using the ISCSI (Internet small computers system interface).

• ISCSI uses conventional devices and cabling to implement data sharing.

• Light Peak provides multi-protocol high-performance communications (10Gbps bandwidth) at extremely low cost and thus is an appealing alternative.

Existing Technology-ISCSI

• ISCSI links storage devices on remote servers essentially emulating local storage bus over WAN.

• Uses existing infrastructure and cabling to physically connect the systems.

• Initiator- It deploys SCSI commands over an IP n/w. This can be done by hardware or software means.

• Target- It is a storage resource located on an ISCSI server.

• Storage array-The target resides here. It provides distinct ISCSI targets for numerous clients.

Proposed Technology-LBLK

• In LBLK, we leverage Light Peak technology-a new optical interconnect technology developed by Intel.

• The initiator directly communicates with the Block I/O (BIO) layer, bypassing the SCSI subsystem and I/O scheduler.

• LBLK also employs a much simpler command set to reduce complexity.

• The BIO translates these requests into data flow requests.

• LBLK uses a lightweight communication protocol to provide in-order and reliable delivery service.

Working-Thunderbolt tech

• It combines PCI Express and Display port into a serial data interface that can be carried over longer and less costly cables.

• The Thunderbolt cable contains a pair of optical fibers that are used for upstream and downstream traffic.

• The cables can carry any form of i/o.

• Thunderbolt technology is equipped with full-duplex links.

• Unlike bus-based I/O architectures, each Thunderbolt port on a computer is capable of providing the full bandwidth of the link in both directions

• The technology functions using the standard drivers present in most OS’s of today.

• All the features necessary to implement Thunderbolt are integrated into a single chip,

Thunderbolt Controller

LBLK• First, the driver in the storage initiator is designed to run on lower-

performance processors.

• The initiator can directly communicate with the Block I/O.

• The command set is much simpler and reduces complexity.

• The new command set includes the following commands: Get partition, Map partition, Read, Write, Get time.

• Block I/O layer issues a read BIO then directly skips to the data blocks skipping the i/o scheduler and request queue .

LBLK Architecture

Comparison

Offers bandwidth of around 1Gbps. Offers bandwidth of up to 10Gbps

High CPU utilization. CPU utilization is up to 30% lower.

Uses obsolete i/o scheduling methods which becomes unnecessary for high performance SSD’s.

Obviates the need for i/o scheduling since the bandwidth offered is so high.

Security offered is minimal and involves only the most basic clear text protection et al.

Data will be encrypted in all but the most basic lightpeak setup.

Considerable overheads between initiator and Block i/0.

Direct connection between initiator and block i/o.

LBLKISCSI

CPU utilization

Performance comparison

Advantages

• Extremely high bandwidth of up to 10GBps.

• Direct access to the Block i/o bypassing the SCSI subsystem and I/O scheduler reducing the overhead involved.

• Up to 2x increase in performance over comparable ISCSI systems and 30% less CPU utilization.

• LBLK achieves better fairness than ISCSI at a considerably reduced cost.

• Much simpler command set.

Disadvantages

• The big disadvantage to Light Peak is compatibility.

• USB 3.0 is backward compatible with USB 2.0 which is the most widespread interface for computer peripherals. Light Peak would require a completely new set of peripheral devices to take full advantage of the interconnects speed and capabilities

Future Scope

• New devices could be modeled around lightpeak technology to take full advantage of the advances it offers.

• The technology will, in all probability replace USB 3.0 as the industry standard for high performance interconnects.

• Cabling is currently implemented using fiber optics. Copper cabling is in contention as a cheaper alternative.

References

• S. Addagatla, M. Shaw, S. Sinha et.al., “Direct network prototype leveraging Light Peak technology”.

• Intel Corporation, Light Peak Technology, http://www.intel.com/go/lightpeak/index.html

• J.Katcher, ”PostMark: A New File System Benchmark”, NetApp Technical Report TR-3022

Thank You

Questions??