For years now, 3.5 inches has been the reigning size of disk drives for enterprise storage arrays. Now, however, smaller, more efficient 2.5-inch SFF (small form factor) drives are proving viable challengers to their larger brethren.
Infortrend's recently released EonStor B12S storage array makes a convincing case for 2.5-inch drives: Instead of housing traditional 3.5-inch disks, it comes with up to 12 SAS (serial attached SCSI) SFF drives. The end result: a system that delivers performance and reliability comparable with large arrays -- not to mention a variety of redundancy features -- and all within a smaller footprint and with lower energy consumption.
Give a drive an inch
Over the years, vendors have found ways to squeeze more capacity per square inch into drives at an astounding rate. As a result, 3.5-inch drives are now capable of 1TB of capacity. While SFF drives today have maxed out at 500GB, they're making capacity gains at a similarly rapid pace. I wouldn't be surprised if they go past a half terabyte capacity by the time you read this.
Although lagging behind 3.5-inches drives in terms of capacity, SFF drives have kept pace with performance. In fact, you can buy 15,000-rpm SFF drives in the same 36GB, 74GB, and 146GB sizes available on the larger units.
The recent shift from parallel protocols such as SCSI to serial protocols such as SAS and SATA (serial ATA) has also made smaller drives more palatable for corporate storage deployments. These protocols use smaller cabling and connectors than SCSI, enabling storage vendors to take full advantage of the contained SFF drives' dimensions when building a storage box.
Bring together all these factors and a storage enclosure based on small drives, such as the Infortrend B12S, becomes not only possible but a much-needed option that can save on energy cost and space in already crowded and power-starved datacenters without sacrificing performance and reliability. Notably, Infortrend was the first vendor to market with a storage enclosure based on SFF drives, but Xyratex announced a 2U enclosure soon after.
A healthy shot of B12S
For my evaluation, Infortrend sent me a B12S with SAS connectivity, filled with 12 Seagate Savvio 15K.1 SAS drives. At 72GB per drive, the configuration gave me a nominal capacity at the host of a little less than 700GB. By mounting 146GB drives, you can double that capacity. For larger requirements, consider adding expansion modules on which you can mount large SATA drives. You can daisy-chain up to three additional modules starting from a dedicated SATA connector on the B12S controller.
The B12S drives are lined up in two rows on the front of the unit. There, you'll find separate control LEDs for each drive, along with a minuscule control panel that swings open to ease access to the drives.
On the back, the EonStor B12S mounts two dual-port RAID controllers, two power supply units, and two cooling modules, providing a level of redundancy that protects the array from single-component failures.
Notably, all the components of the B12S are petite in format, not just the drives, which makes the array one of the lightest I ever had to lift: about 45 pounds, without mounting rails.
SAS connectivity doesn't favor attaching many hosts to the array. If you plan to have more than a couple of servers, opt for the FC model and a compatible switch. At the moment you cannot buy a SAS switch, although LSI Logic has been showing a prototype for some time. In my case, I installed one LSI Logic SAS adapter on each of my two Windows Server 2003 machines, connected each adapter to a separate B12S controller, and I was ready to go.