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Issue of April 2004 
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User Case Studies

From DAS to SAN

NSE.IT manages the largest stock exchange in the country and a storage infrastructure to match. Here's a look at its storage infrastructure that manages the large volumes of traffic daily. by Minu Sirsalewala

NSE.IT uses a state-of-the-art enterprise IT infrastructure in order to manage infrastructure for various stock exchanges in India. But in the beginning, the storage system at the company comprised DASs attached to every server. The disks were SCSI-based and a maximum of seven disks could be attached to each server.

The average disk utilization on the higher side would be up to 90 percent resulting in under-utilization of disk space. The problem was further compounded due to limited expandability. And there was also an issue that each server could only have one OS.

Volumes on the fly

The growing storage and accessibility demands were not being met by the existing DAS system. Uday Nadkarni, Group Head, NSE.IT Limited explained that to keep up with burgeoning business there was a need for centralized disk storage with 100 percent utilization of disk space. A lot of space was being wasted, as there was no allocation/reallocation of volumes on the fly.

"As the company had a heterogeneous environment we felt that co-existence of multiple OSs in the storage architecture was much needed," said Nadkarni.

Another issue the company faced with the DAS system was that, the system did not allow hot-swappable peripherals and parts. The company needed a 100 percent fault-tolerant disk subsystem that would allow LAN-free backup.

Go for SAN

With its ever-increasing storage demands the company decided to deploy a SAN. This architecture would help the company effectively utilize the disk subsystem in a fault-tolerant mode and make data available all the time.

The design

Nadkarni said that they had set very stringent guidelines about the performance expectations of the new architecture. The following factors were considered before getting down to design the SAN:

  • Scalability of the new architecture
  • Performance of the network
  • Connectivity and manageability of the network system
  • 100 percent availability and fault tolerance

Components of the network

The SAN architecture at NSE.IT constitutes a variety of hardware and software components.

Hardware components:

  • HBA Cards
  • SAN switches
  • Fiber ports & Cables
  • Enterprise storage boxes with redundant cache memory
  • Hot-swappable peripherals and parts Software components:
  • Device drivers for HBA cards
  • Zoning and LUN masking
  • Centralized monitoring and administration tools
  • True copy
  • Shadow image or Flash copy
  • Security volume manager

Distinct architecture

According to Nadkarni, NSE.IT's SAN architecture is unique in many ways. It has centralized storage, scalability, and online allocation/reallocation of storage space. The architecture also gives 100 percent uptime and availability with co-existence of multiple OSs like Linux, Windows, and Unix.

Lower TCO higher ROI

The deployment of a SAN architecture has introduced significant benefits to the company on both technology and business fronts. The business benefits realized are higher ROI, lower TCO, and significant increase in throughput.

The technology benefits have been effective utilization of disk space, increase in data throughput, and server consolidation. The Fiber Channel-based subsystem has largely increased the throughput and has helped to reduce the existing backup window by half.

"With server consolidation it is now possible to centralize management of the storage network. The network also supports heterogeneous OSs," said Nadkarni.

Future architecture

The enterprise SAN solution along with Unix servers is currently used in the production environment where the company has already experienced productivity gains. Nadkarni expressed the intention of extending the concept to the development environment, as there is the flexibility to effectively utilize disk space for various projects in a heterogeneous environment.

 
     
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