[RndTbl] RAID5 rebuild performance

[Sean Cody]

Yup.  That makes sense.  Raid 10 does't involve a parity calculation.  Raid 10 is stripe and mirror so it's single read to single write.  Raid 5 is multiple reads to single write on rebuild.  Comparing the two for rebuild is an apples to oranges kinda thing.

-- 
Sean (mobile)

On 2011-05-19, at 2:47 PM, Kevin McGregor <kevin.a.mcgregor at gmail.com> wrote:

> Did that, no effect. Building a RAID10 array of 14 10K disks (including two hot spares, so really 12 disks) on the same controller (different channel, not at the same time as the RAID5 rebuild) gives ~130,000 KB/sec.
> 
> On Thu, May 19, 2011 at 1:57 PM, Gerald Brandt <gbr at majentis.com> wrote:
> Linux has speed limits on rebuilds, check
> 
> 
> /proc/sys/dev/raid/speed_limit_max
> 
> /proc/sys/dev/raid/speed_limit_min
> 
> and echo new values into there.
> 
> Gerald
> 
> 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 right order of magnitude? I though it should be higher, but I haven't set up such an array before, so I don't have anything to compare it to.
> 
> If it's slow, does anyone have a suggestion for speeding it up?
> 
> Kevin
> 
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