IBM unveils hefty storage controller

Previously known as "Lodestone," the product is "mostly software" but is to be sold with specially configured X-Series IBM servers to ensure reliability, lead architect Steve Legg said.

The SAN Volume Controller (SVC) uses four 2-gigabit-per-second Fibre Channel interfaces, a 4GB cache and dual 2.4GHz Pentium 4 chips to manage heterogeneous hard-disk storage independently of application servers--which is known as storage virtualization.

Storage virtualization is a method of disk management in which the physical details of the hard disks are hidden by a controller from servers on a network. In a loose analogy, this is similar to building an Olympic-size swimming pool out of a series of puddles. The controller can organize 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 1 million gigabytes) in size.

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

The SVC is an in-band virtualizer, which means it handles all the file data itself. By contrast, out-of-band virtualization tells servers where to read and write data, but then lets them do it directly. These two approaches divide the virtualization community.

"In-band does increase latency, but it gives us complete control over the storage network, which is necessary for high availability and guaranteed performance," Legg said. "Quality of service is much easier to deliver."

Legg added that SVC, which runs IBM's Little Blue variant of SuSE Linux, manages consistent throughput of 1gbps for data.

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," Legg said, "it's in making it reliable when things go wrong."

The system has been tested with heterogeneous hosts, including Linux and Windows on Intel processors, IBM's AIX, Hewlett-Packard's HP-UX and Sun Microsystems' Solaris, as well as various storage area networks (SANs), such as Brocade, McData and Inrange.

Legg said the system has been tested on a limited number of hosts so far. "But in the long term we'll support many more," he said.

More details of qualification procedures will be available closer to the product's launch, which is expected toward the middle of 2003, and further details are expected at the end of April. The price hasn't been set yet, but IBM said it is considering an entry-level cost of around $94,000.

ZDNet UK's Rupert Goodwins reported from London.