San Francisco - 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 inchOver 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 B12SFor 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.
Light on size, not featuresThe B12S may be small, but it offers a set of management tools that, if not best in class, challenges many competitors. In addition to the small, easy-to-navigate control panel, I had the option of a CLI, a browser-based GUI, and SANWatch, a Java-based application.
All the management interfaces are functionally equivalent, so after setting an IP address consistent with my network using the control panel, I was able to switch between the browser and SANWatch with ease to manage the array. Thanks to the GUIs' intuitive designs, I had no trouble provisioning storage, monitoring the status of the hardware, or keeping an eye on the workload. One major difference between the two: The browser version lacked the rich and detailed online help I found on SANWatch.
I liked that you can create separate passwords for read-only access, maintenance tasks, and configuration, but other aspects of the security tools need improving. For example, I was able to change a password without having to type the previous password, which means that anyone passing by an unattended console could do the same. Despite these few glitches, the B12S's management tools are capable and easy to use.
The B12S maintains a detailed event log that traps error conditions and triggers the onboard alarm with custom thresholds. In addition, you can send critical warnings to an admin using messaging systems such as e-mail or SNMP.
Although not the most polished I have seen, the management tools of the EonStor B12S are adequate to the task. However, I was more interested measuring how fast the B12S could perform and how much energy it would use.
For that series of tests, I used SANWatch to create logical drives, each containing six physical drives in RAID5 with no spare. In a typical setting, a spare disk would, of course, be a good idea, but I wanted to make sure that all drives were spinning and using power during the test.
I assigned each logical drive to one of my servers, then I began running Iometer scripts to stress the number of I/Os per second and the transfer rate. During those test runs, my Watts Up Pro hardware meter was recording the power used by the array only.
Power performancePerformance-wise, the EonStor B12S fared well, rivaling results I've seen from arrays with 3.5-inch drives that use similar technology. This didn't surprise me in the least. I was, however, surprised by just how low the B12S's power consumption proved to be. When idle (i.e., while neither reading nor writing data), the B12S consumed a mere 235 watts, remarkably less than the 380 watts I have measured on arrays with 3.5-inch drives and similarly redundant, six-drive configurations. Another interesting fact is that the workload doesn???t add much to the baseline, only a few watts more. In fact, the increment is almost perfectly linear with the block size increase, with a few spikes when the cooling modules of the array start spinning the fans faster, which happened, for example, when the room temperature would temporarily drop a degree or two below 75 F. Even at the highest stress level I measured — during sequential writes of 64K blocks — the B12S drew a mere 254 watts. See my Iometer results at various block sizes and their corresponding power consumption figures.
Infortrend offers an interesting approach to pricing: Unlike other vendors' arrays, Infortrend's enclosure doesn't mount drives with proprietary connections. Thus, you can purchase the enclosure (the one I tested costs just under $8,000), then procure your own drives separately.
I enjoyed reviewing the Infortrend EonStor B12S and I would not hesitate to recommend it for consideration for shops where its capacity and other features fit your requirements. Boasting performance in the same ballpark as traditional arrays, a power draw that is roughly 60 percent less, and an overall form factor just half the size, the B12S can be an offer too good to pass on.