Enterprise storage software: case histories; jump into the pool

Software Magazine, Summer, 2002 by John P. Desmond

The lab decided to bring in software from Veritas just before Askinazi joined three years ago. "Now we have consolidated into eight home directories. Every time we want something to grow, we tack on another 50Gb to give everyone more room, and we don't have to shut anyone down," he says.

In the Veritas system, a disk is known by the operating system as a fixed name, dependent on a hardware path. A disk can be divided into partitions, which are permanent as long as some data is on them. Once the disk is brought under the control of the Veritas Volume Manager, it becomes a Veritas resource and can be manipulated by the software. A public partition, called a "subdisk," encompasses the entire disk and allows the user access to all or some of it.

Once the subdisk is used to mount a file system, the partitions enter the virtual pool and thus can be dynamically resized. A file system may be greater than the size of a single disk, making necessary the idea of a "plex," which is the ability to glue pieces of storage together logically. Depending on the method chosen, the file system can grow beyond the limitations of a single disk drive, and may offer better performance if multiple disks are set up to write at once.

If an organization wants to mirror its data into multiple copies, it must accommodate data "volumes" of one or more plexes. In the Veritas system, a disk group is the unit of portability for Veritas Volume Manager. A group of disks can be moved between machines regardless of the operating system or specific hardware. The Volume Manager pulls it together.

One pitfall to avoid is grouping direct-attached storage devices with SAN devices, which are easy to redirect. In the event of a server failure, it would be difficult to import the disk group to another host if some of its objects were missing.

"Veritas takes the disk in and lets you move pieces around any way you want. If the disk is failing, it relocates data to another area that is available," Askinazi says.

Seeking Two-Terabyte File System Support

While the lab's experience with Veritas has been good, Askinazi would like to see Veritas extend its products to address a two-terabyte file system. "I need it now; I'm in wait mode," Askinazi says. "The name space is there. I don't know what's taking them so long."

Brookhaven is testing the Linux version of the Veritas product now. The state of storage tools in the Linux environment is well behind other platforms, Askinazi suggests, but Veritas is ahead of most of its competition in supporting Linux. Once Linux support on the servers he needs is improved, Askinazi anticipates spending on the order of $6,000 per server instead of the $30,000 per server he pays now. "I'm looking to get Veritas running on all our platforms so there is portability."

The scientific community tends to push the limits in computing, and tends to operate with a small but highly expert IT staff. Askinazi estimates that the Veritas software is saving the Lab the cost of half a person. "Anytime we can find a software package that allows the people we have to be more productive and save us a seat, that's what we would prefer," he says.