The SAN Storage Expanded

by John Chan
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Back in Feb 2001, the University studied and adopted the Network Storage System (NSS) as the standard platform for providing central storage. The advantages of using the NSS include the provision for high availability and disaster recovery capability, the simplification of the backup process by sharing multiple tape drives among various servers, the provision of data sharing among multiple servers, and the flexibility of storage management and expandability. Since then, the Storage Area Network (SAN) was purchased from the EMC Inc. and implemented as the infrastructure backbone for the NSS.

The SAN infrastructure was fully operational in Sep 2001 using the Symmetrix 8730 hardware storage subsystem with 6TB raw storage. Initially, it was decided that some of the mission-critical central hosts will be connected to the SAN, and later to cover most of the other central hosts providing vital services. As the data size requirement for each user and application has grown over the years, together with the need of connecting other hosts to the SAN, it is necessary to expand the existing hardware storage subsystem.

During the upgrade process, it was decided to use Tier-1 storage for all of the mission-critical hosts, and Tier-2 storage for those vital servers. At the present stage, the Tier-1 storage will comprise of the Symmetrix DMX 1000 subsystem and 13TB raw storage, while the Tier-2 storage will be using the Clariion CX700 subsystem with around 6TB raw storage. The Clariion subsystem, which is considered to be a cheaper class than the Symmetrix, will provide more cost-effective solutions for these systems. The CX700 can accommodate the fiber channel disks and the ATA disks, the latter is considered to be an even more cost-effective storage which is very suitable for data archiving. Furthermore, through storage virtualization, both the Symmetrix and the Clariion subsystems can be used in the same host, which is a very flexible solution for data sharing, and both can share the same centralized backup subsystem without affecting each other.

With this upgrade, users would be able to enjoy faster and more reliable data storage, and a much larger storage quota for most of the University's activities. Services that enjoy these benefits include the some of the administrative systems, the email services, the web services etc. More will be added in the future.