[mythtv-users] OT: RAID6?

Steve Hodge stevehodge at gmail.com
Mon Nov 13 02:31:54 UTC 2006


On 11/13/06, John Drescher <drescherjm at gmail.com> wrote:
> > Actually, for RAID5 + hotspare vs RAID6, you _should_ get slightly
> > better read performance with RAID6 due to having an extra drive in the
> > array.
> >
>
> I don't think so. For example a raid6 with 6 drives 4 contain data and 2
> contain parity for each raid block this. For raid 5 with the same 6 disks, 4
> contain data, 1 contains parity and 1 contains nothing of value for each
> raid block. The thing is I do not believe the raid subsystem makes use of
> the parity for reads unless a drive is bad. I may be wrong on this one
> though. For writes obviously the raid 5 is faster.

But the parity is distributed across all drives for both RAID5 and
RAID6. So if you're reading more than one block RAID6 can be faster.
For instance, if you are reading 6 blocks, with RAID 6 they may all be
on different drives and so able to be read simultaneously. With RAID 5
at least one drive must hold two of the blocks.

Steve


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