June 21, 2010, 11:01 AM — Storage area network (SAN) technology has been around since the late 1990s, but historically it was priced far out of the range of small IT departments. Now this option for making more-efficient use of data storage has become affordable for all but the smallest of IT shops.
For example, Internet Small Computer System Interface (iSCSI) SAN arrays such as the Drobo Elite cost $3500, and the Dell PowerVault MD3000i starts at just over $5000.
SAN devices are disk arrays located on a network storage device shared with multiple servers--up to 16 servers, for these models. To each server operating system, however, the storage that a SAN device provides appears to be dedicated, not shared.
It used to be that when you bought a server, you guessed how much storage you would need, and then bought disks based on that often-underestimated number. When your needs outgrew your disk capacity, you had to back up the server, replace the disks, and restore the data.
With a storage area network, however, you buy only as much storage as you initially need, and then expand as you go. This save your company money in hardware costs and energy consumption, and it reduces IT personnel workload and system downtime.
For a small business, high-throughput, low-latency fiber-channel-based SANs are still too pricey. But less-expensive iSCSI SANs, which use standard ethernet cables, network cards, and switches, have no trouble keeping up with the disks that small and medium-size companies are likely to use.
iSCSI, a protocol for connecting storage devices using the IP protocol and SCSI commands, replaces expensive SCSI cards and cables with ubiquitous ethernet hardware, and permits multiple computers to connect to a single drive array. With iSCSI, your storage location no longer needs to be close to your servers. Since ethernet cables can be up to 100 meters long, you can place a SAN wherever you like.
A key feature of SANs is "thin provisioning," which in effect lets you lie to your server about how much storage is available to it. For example, you can fool each of five servers into thinking that it has 16TB (terabytes) of dedicated storage available when in reality your SAN has a total of just 2TB of actual disk space.
Of course, you'll still have to add drives to your storage area network as your total data approaches capacity, but thin provisioning helps you avoid wasting space on underutilized servers or creating new partitions each time you add a physical disk.