Adaptec Serial ATA II RAID 2820SA review

LSI Logic delivered the first SATA II RAID controller to market six months ago, so it's surprising it's taken arch-rival Adaptec this long to catch up. Nevertheless, the 2820SA remedies the situation and heralds a family of four new adaptors that all support 3Gb/sec transfer rates.

Unlike the AMCC 9550SX-8LP controller, Adaptec supports NCQ (native command queuing) but not port-multiplier technology. This is no big deal for the type of apps the 2820SA is aimed at and Adaptec does make up for this in other departments. The card offers the standard range of RAID arrays, but with Adaptec's Advanced Data Protection Suite (ADPS) in place the card will be able to support the latest RAID6 and 60 arrays. These require a minimum of four drives, as they use the capacity of two for redundancy, but can survive the loss of two drives. ADPS brings in other goodies, including Adaptec's proprietary 1E striped mirrors and a snapshot backup facility. The only drawback is ADPS won't be made available until later this year and Adaptec wouldn't give us a launch date.

The 2820SA is a half-height PCI-X card, so it's aimed at pedestal and rack-server apps. Size for size, it's slightly wider than the AMCC 9550SX-8LP and, although it comes with an extra low-profile backplate, the documentation does advise it may not fit in all low-profile systems. It's equipped with 128MB of embedded cache memory. This can't be upgraded, but, as with AMCC, Adaptec offers an optional battery backup pack. A big difference is all eight of the SATA port positions, as Adaptec has arranged them in a line along the side of the card, making access easier.

For local and remote management, there's little to separate AMCC's 3DM 2 and Adaptec's latest Storage Manager utility, as both offer good levels of access to the controller, arrays and drives. Storage Manager allows arrays to be created on-the-fly and new disks designated as hot spares or added to existing arrays. Error notification extends to sending messages to multiple email addresses. As with 3DM 2, Storage Manager can manage local and remote RAID controllers, although it doesn't offer support for encrypted HTTPS sessions for the latter.

For performance testing, we installed the card in a 133MHz PCI-X slot in a Supermicro dual 2.4GHz Xeon system with 2GB of memory and running Windows Server 2003. We used Western Digital's WD2500 3Gb/sec SATA hard disks and the open-source Iometer utility configured with two workers and 64KB sequential read requests. With a single drive attached, the 2820SA returned an impressive 94MB/sec raw throughput. With two Western Digital drives configured in a RAID0 stripe we saw performance rise to 161MB/sec, and with a three-disk RAID0 stripe we saw it deliver 188MB/sec. Raw throughput was noticeably better than the 9550SX-8LP for one and two drives, but AMCC pulled ahead by delivering a marginally better read rate of 206MB/sec.

The 2820SA shows that SATA II is a solid alternative to SCSI in SMB and mid-range storage apps. Adaptec's RAID management and monitoring features are a cut above those offered by AMCC, and the promised ADPS of features will give Adaptec a big edge over the competition.

Author: Dave Mitchell