[RndTbl] RAID5 rebuild performance

Trevor Cordes trevor at tecnopolis.ca
Thu May 19 17:25:09 CDT 2011

On 2011-05-19 Kevin McGregor wrote:
> I installed Ubuntu Server 10.04.2 LTS AMD64 on a HP ProLiant ML370 G3
> (4 x dual-core/hyperthreaded Xeon 2.66 GHz, 8 GB RAM) and I used the
> on-board SCSI controller to manage 8 x 300 GB 15K RPM SCSI drives in
> a software RAID 5 set up as a 7-drive array with 1 hot-spare drive.
> All drives are the exact same model with the same firmware version.
> It's currently rebuilding the array (because I just created the
> array) and /proc/mdstat is reporting "finish=165.7min
> speed=25856K/sec". Does that sound "right" in the sense that it's the

I got around 20-30M/s or so on my RAID6 7200rpm 12TB 8-disk rebuild this
week.  That was on an old Pentium-D but with a nifty zippy new 8-port
SATA card.  Your speeds sound a touch slow, given the hardware.  But
RAID5/6 does weird things behind the scenes.

Note, if you're doing 8 drives anyhow, why not RAID6?  Its
survivability is much higher and its performance is surprisingly nearly
that of RAID5 (there's some graphs somewhere I was recently looking
at).  The only downside is degraded performance sucks, but hopefully
you will never be in that state (long).  I've personally had/seen 2
RAID5 failures and will never use anything except RAID6 now.

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