Geek question: RAID array performance

[andygates]

We've got a big data store. It's currently built as a single max-size 2Tb RAID 5 array over 11 disks. It performs like a three-legged dog and each of the 300Gb disks has about 75Gb unused (because that would take it over the 2Tb SCSI RAID limit).

We need to rebuild it. We've been advised that volume sizes over 1.5Tb are dogs under SCSI RAID so we're keen not to do that. Our options are:

* RAID 10, 10 disks+hotswap, total volume space 1.5Tb, good write performance.

* RAID 5, 7 disks+hotswap, total volume 1.6Tb, but it feels wasteful of all these lovely disks.

* Two smaller RAID 5 volumes, 4+hotswap and 5+hotswap, giving us .9 and 1.2 Tb respectively. The volumes should behave better, because they're smaller and on fewer disks, but will this just move the bottleneck up to the servers' RAID controller?

Gurus, your wisdom is much appreciated!

Comments

[gedhrel.livejournal.com]

Incidentally for the 500GB disks in our high-density kit we've tended to allocate 2 pool spares per 14-disk row; mostly because of the pain assocaited with a physical replacement.