Proper stride and stripe-width for RAID 50
Andreas Dilger
adilger at dilger.ca
Tue Jun 5 16:18:35 UTC 2012
On 2012-06-05, at 10:12 AM, David Shaw wrote:
> I've been looking around, but can't seem to find an authoritative statement on setting stride and stripe-width for RAID 50 (i.e. a RAID 0 over multiple RAID 5s)
>
> Based on my understanding of what stride and stripe-width set, it seems to me that it should be calculated the same as it would be if there were no multiple-level RAIDing involved. For example, given a RAID 50 made up of two 3+1 RAID 5s striped together (so 8 disks total) with a 512k chunk size and 4k block size, the stride should be 128 (512 / 4) and the stripe-width should be 768 (stride * 6 data disks).
Strictly speaking, you only need a stripe-width of 384 (stride * 3 data
disks) since this is the minimum read-modify-write boundary.
That said, why not configure your system with RAID-6 6+2? This gives
better fault tolerance than RAID-5.
> These settings should work equally well whether the two RAID 5s are striped together or just appended one after the other via LVM.
>
> Is my reasoning correct?
>
> David
>
>
> _______________________________________________
> Ext3-users mailing list
> Ext3-users at redhat.com
> https://www.redhat.com/mailman/listinfo/ext3-users
Cheers, Andreas
More information about the Ext3-users
mailing list