On Thu, May 22, 2008 at 7:12 PM, Guy Boisvert boisvert.guy@videotron.ca wrote:
You do not need two (2) raid controllers unless you want to have redundancy at the controller level. Adaptec, 3Ware, etc do RAID 50. For RAID 50, you need at least 6 disks.
http://en.wikipedia.org/wiki/RAID
For database, i'd go with RAID 10. As pointed out Joseph in a previous post, RAID 5 rebuilding would slows the array down.
As for RAID 10, i didn't make extensive benchmarks but here are the rough results i got with Adaptec 3405 and four (4) Seagate 15K SAS drives:
RAID 5: Read = 170 MiB/s Write = 135 MiB/s
RAID 10: Read = 170 MiB/s Write = 160 MiB/s
And stick with md-raid 10 (also known as software raid) because it is much more intelligently designed than any closed-source-embedded-raid-controller.
Nowadays hardware raid frightens me because of the need to have spare raid-controllers for every hardware-raid-configuration I have. They are neither interchangable nor easily recoverable.
md-raid 10 can be established with any number of disks (at least 3 but better check with google)