IBM shows off two-petabyte storage controller

Virtual storage is the way ahead for really efficient systems, says IBM

IBM demonstrated the result of more than three years' development this week when it unveiled its TotalStorage SAN Volume Controller (SVC) at its Hursley Park, UK laboratories.

Previously known as Lodestone, the product is "mostly software", according to lead architect Steve Legg, but is being sold with specially configured x-Series IBM servers to ensure reliability. The SVC uses four 2 Gb/s FibreChannel interfaces, a 4GB cache and dual 2.4GHz Pentium 4 to manage heterogeneous hard disk storage independently of application servers -- storage virtualisation, in other words, one of the hot topics in current SME systems design.

Storage virtualisation is disk management where the physical details of the hard disks are hidden by a controller from servers on a network. The controller can organise caching, reaction to faults, storage attachment and removal, as well as security, backup and other management issues, by bringing disparate devices together into components of one unit of storage, a single virtual disk drive which in the SVC can be up to 2 petabytes (roughly a million gigabytes) in size.

This leads, says IBM, to better resource utilisation, easier management and more efficient use of system administrators' time.

The SVC is an in-band virtualiser, which means it handles all the file data itself. Out-of-band virtualisation tells servers where to read and write data, but then lets them do it directly. This is a religious schism in the virtualisation community: "In-band does increase latency, but it gives us complete control over the storage network," said Legg, "which is necessary for high availability and guaranteed performance. Quality of Service [QoS] is much easier to deliver."

He said that the SVC ran Little Blue, an IBM embedded variant of SuSE Linux, but with no OS calls in the data path: it managed 1Gbps consistent throughput.

The SVC is designed to work with other companies' hard disks, although it is currently only qualified for two types of IBM storage. "The difficult bit isn't in making it work when things go well," said Legg, "it's in making it reliable when things go wrong."

The system has been tested with heterogeneous hosts -- Intel Linux and Windows, IBM AIX, HPUX and Solaris -- and various SANs, such as Brocade, McDATA and Inrange.

"The test matrix is horrible, but in the long term we'll support many more," said Legg.

More details of qualification procedures will be available closer to launch, which is expected towards the middle of 2003, and a further release of details is expected at the end of April. Pricing hasn't been set yet, but IBM said it was thinking of a ballpark entry-level cost of around £60,000.


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