Brad Knowles wrote: > Keep in mind that if you've got a five disk RAID-5 array, then for > any given block, four of those disks are data and would have to be > accessed on every read operation anyway, and only one disk would be > parity. The more disks you have in your RAID array, the lower the > parity to data ratio, and the less benefit you would get from > checking parity in background. My understanding is that this is true only when the system is running in a degraded mode. When you blow a disk, instead of hitting that disk, you access all the other disks and calculate the desired block using the parity. If this system is healthy, a single disk access should be sufficient. If a system with a 9 disk raid5 volume (pretty common) had to hit each disk on a block access, it would majorly suck. I think detecting and handling bad physical blocks is a whole other matter. Richard Coleman rcoleman_at_criticalmagic.comReceived on Mon Nov 01 2004 - 14:58:31 UTC
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