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Unified Serial RAID Controllers for PCIe

Atto Express SAS R348

Atto offers two PCI Express based RAID 5 SAS/SATA controllers: the R380, which has two high-density ports for up to eight devices, and the R348, which has one port for four external devices (SFF 8088) and two ports for up to eight internal devices (SFF 8087). However, you can only use a maximum amount of eight ports, whether internal or external. According to the Atto website, this feature is still unique; hence, we had a look at the R348, because we consider it more flexible than the R380.

Some drawbacks first: this controller does not support RAID, and it does not offer such extensive operating system support as the Adaptec. It also only has a two-year manufacturer warranty, whereas Adaptec, ICP and Ciprico/Raidcore come with a three-year warranty. We were also told that the controller’s default settings may not provide the best performance - unfortunately, this message arrived after we had finished testing. The feature called RGSSpeedRead will enable read look-ahead for RAID drives, but this setting has to be activated via a command line interface; we found a brief description of this feature on one of the last pages in the manual. We did not have the time to repeat all the tests, but read performance clearly improves once RGSSpeedRead is enabled. It’s a pity that Atto doesn’t enable it in the factory, or at least devote a small chapter on performance tuning in the manual. The R348 has a Java-based interface, which is easy to use, but does not give you too many options. We also didn’t understand why users are forced to register with Atto before they can download anything.

Like the other cards, the Express SAS R348 is a low-profile PCI Express add-on card that utilizes eight PCIe lanes. Unlike Adaptec and ICP, though, this card carries 256 MB or DDR2 memory with ECC. It also uses the more advanced XScale processor IOP 348, which runs at 800 MHz. It provided good, though not excellent I/O benchmark results.

Feature wise, this RAID controller Atto supports all important RAID modes: 0, 1, 10, 5, 50. It can also run JBOD mode and even RAID level 4, which stores all parity information on a single hard drive. Unlike RAID 3, a RAID 4 creates stripesets using larger data blocks instead of the single-byte stripes of RAID 3; this gives RAID 4 a performance advantage over RAID 3. RAID 6 and 60 are not supported yet, but Atto says it will follow up soon with these. The same applies for an optional battery backup unit, which is not available yet. Windows Server 2003, Windows 2000, Windows XP and Windows Vista, Max OS X 10.4 and three different Linux distributions are supported, but not Solaris, FreeBSD or Netware.

You have to register with Atto before you can download any software updates.