Adaptec's Serial ATA II RAID 2820SA is a 64-bit PCI-X add-on card for server and workstation environments. It comes with a nice feature set and is priced at $575 (MSRP); the interesting RAID 6 option is part of an add-on called the Advanced Data Protection Suite. In addition to that, there is the option to add a battery backup unit (BBU), with both charged separately.
The basic RAID features are comprehensive: A regular retail kit will support RAID modes 0, 1, 10, 5 and 50, hot spares, and RAID level migration and online capacity expansion. In addition to the software features, the package includes eight SATA cables (one for each port), a bootable CD with Adaptec's Storage Manager, drivers for Windows, Linux, Netware and FreeBSD, as well as a low-profile slot cover. The card itself has a low-profile form factor, but the SATA connectors will make it difficult to attach cables inside some low-profile servers (2U, 3U) because they are all directed upwards. As a result, you might want to obtain SATA cables that have 90° bends.
While Adaptec used to deploy third party Serial ATA controllers, this one is based on the AIC-8210, which was designed in-house. It hosts the PCI-X interface, the RAID unit called the Adaptec RAID Code (ARC) and eight Serial ATA ports with support for Serial ATA 2.5 features.
As already mentioned, support for RAID 6 comes separately. The so-called Advanced Data Protection Suite includes support for the following features:
- Copyback hot spare / hot space
This means that the controller will automatically rebuild a degraded array using a previously-defined drive, and restore the original configuration as soon as the faulty one is replaced.
- Striped mirror (RAID 1E)
The controller will simply mirror RAID 1 data onto a stripe set in order to further increase read performance while maintaining the (good) write performance levels of a single drive. Here it makes sense to pick a main drive that has double the capacity of the mirror stripe set members.
- RAID 6, 60
RAID 6 should sound familiar to you by now. A RAID 60 combines RAID 6 and RAID 0 by striping two RAID 6 arrays. This decreases data safety, but the probability of losing three RAID 6 array drives within a short time is relatively low.