By Dave Simpson
—AMCC may be one of the last controller manufacturers to add support for RAID 6, but the company claims that the wait was worthwhile because its 3ware 9650SE SATA-II RAID controller virtually eliminates the write penalty typically associated with RAID 6.
Scott Cleland, AMCC's director of marketing, says the performance penalty of the 9650SE controller with RAID 6 enabled is less than 10% compared to RAID 5, and that competitors' controllers can have a performance degradation of up to 30%. (However, the claims of those competitors range anywhere from 2% to 15% in terms of the RAID-6 performance penalty.)
RAID 6 has an inherent performance penalty because it requires two sets of parity calculations to protect against the simultaneous failure of two disk drives in an array. AMCC's 9650SE overcomes this, to a degree, by running the two parity calculations (P and Q) at the same time.
It should be noted that in some of the applications for which SATA-based arrays are used, such as secondary storage, the RAID-6 performance penalty may not be an issue for end users.
AMCC claims a RAID-6 sustained write performance of more than 600MBps, and a read performance of more than 700MBps, in a 16-drive configuration. Unlike some competitors that rely on Intel components, AMCC manufactures its own hardware.
The 3Gbps SATA-II 9650SE controller is available with 2 to 16 ports (with a 24-port version due in the first quarter of next year), supports the PCI Express host bus, and is based on the eighth generation of AMCC's StorSwitch non-blocking switch fabric architecture.
Suggested list price for a 4-port 9650SE controller starts at $395, or $995 for a 16-port configuration.
AMCC competes with controller manufacturers such as Adaptec, Areca, Arena-MaxTronic, Infortrend, LSI Logic, Promise, and Xyratex.
Although RAID 6 has been available for years from major manufacturers such as Hewlett-Packard and IBM, it is gaining end-user interest due to the popularity of SATA-based disk arrays. In some cases, users want RAID 6 for their SATA arrays because of the long rebuild times associated with the high capacities of SATA drives (500GB and, more recently, 750GB), and in other cases because of the perceived reliability issues associated with SATA drives.
For more information on RAID 6, see SATA spurs RAID-6 activity.