A Compelling SAN For IT

When Storage Center 4.0 arrived in our lab, we had to ask: "Who is Compellent?" Founded in 2002 by a group of storage and virtualization executives, Compellent targets small and midsize businesses that want high-end SAN features and low-end management hassles.

The best audience for Storage Center 4.0 consists of midsize organizations whose storage needs generally scale up through about 50 TB. The company claims it can scale way beyond 50 TB for the enterprise market. Compellent increasingly is competing with the likes of EMC's CX300 series Clariion line as well as NetApp's FAS 2000 and 3000 series storage area network, says Compellent senior marketing manager Bob Fine.

Out of the box, Storage Center has an excellent tiered storage system for a SAN fit for a small or midsize business. What's the big deal about tiered storage? According to Compellent's own research, 80% of data ends up just sitting on file shares, never to be accessed again, after 60 days. EMC cites a similar statistic. Fibre Channel storage is expensive, so to the degree that companies can shift old data to low-cost, secondary storage to save money, they should do so.

Compellent makes this possible with a built-in tiered storage technology. The system defines Tier 1 storage as 15,000-rpm Fibre Channel drives, Tier 2 as 10,000-rpm FC drives, and Tier 3 as 7,000-rpm SATA drives.

Once we defined our storage volumes and attached them to our lab file server, we implemented a default policy in which a file that wasn't touched for three days was moved to Tier 2. If that same file was not touched for another three days, it was moved down to the el cheapo SATA storage tier.

The functionality worked well: Six days after loading our storage array, our data was on the SATA volume. Storage Center also can move older data back to the higher tiers if it's repeatedly accessed.

We then set our sights on an add-on component called FastTrack. The FastTrack feature moves frequently accessed data to tracks on the outer perimeter of the spindle, where the drive head can seek data more quickly, improving overall disk performance. Compellent says that FastTrack is unique in that it moves individual blocks to outer tracks while competitors can move only entire volumes.

Compellent says its lab testing demonstrates improved seek times and disk performance of up to 30%. We couldn't vet this claim because our simple file system was already running on the fastest disk in the array. We weren't able to see a difference in seek times with FastTrack either on or off simply by moving files between systems on and off the SAN. That said, if the FastTrack feature works as advertised, applications that rely on a large amount of disk I/O are sure to benefit from the functionality.

MORE THAN TIERS

Another well-implemented feature is the replication engine's bandwidth throttling and quality-of-service features. While all of the major players offer simple snapshot and replication functionality, what if you need to replicate your data over a WAN link? Storage Center allows you to define a replication schedule that's sensitive to bandwidth.

As a result, admins can replicate critical data off-site and have complete control of when to transfer data, and how much of the WAN link to use for replication. The drawback is that you'll need to replicate with another Compellent SAN to use this functionality.

We were also quite impressed with the way Compellent executed firmware updates. Upgrading code on a SAN is a stressful proposition and usually means downtime while the code is applied. With Storage Center 4.0, you can download and prepare the code upgrade for installation while the system is still running. A three-minute reboot of the array then completes the promotion of the new code into production. For fault tolerance, the firmware is both kept on a standby flash card and striped across the drives in your SAN, so you can easily revert to old code if a problem arises.

One negative we noticed was with respect to the reporting of critical events, such as a failed disk, which is done via TCP/IP. That's not a problem, as long as the network is functioning normally.

In addition, we don't particularly enjoy providing bidirectional communication through our firewall to a critical resource. EMC, by contrast, typically attaches a modem to a private analog line for alerts and remote troubleshooting.

DO THE NUMBERS

Compellent has two models: a 20 series and a 30 series. The main difference between the two is the controller's slot configuration and processing power. The 20 series sports one high-speed PCI-E slot and five slower PCI-X slots. The 30-series sports dual-core processors, five PCI-E slots, and one PCI-X slot.

Our 30-series evaluation unit shipped with the core Storage Center 4.0 controller, along with two storage chassis. Each storage chassis had its own redundant Fibre Channel controller along with redundant power. The storage shelves were connected back to a four-port, 4-Gb PCI-E FC card on the controller. In terms of storage, our first storage cabinet was filled with 15,000-rpm, 146-GB FC drives. Our secondary cabinet came with a combination of 10,000-rpm, 146-GB FC drives and 7,000-rpm, 500-GB SATA drives.

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So how much does Storage Center 4.0 cost? Our evaluation unit, which included most of the premium software features available, along with the hardware described above, lists for around $95,000. According to Compellent, a typical new customer configuration that comes with a single controller and 6.4 TB of disk, with some premium software features enabled, lists for around $49,500.

At those prices, you can land a best-of-breed product like EMC's Clariion. But there's no doubt that if you're in the market for a midrange SAN, Compellent's offering should be on your short list.