CentOS - Jan 2011 - variable raid1 rebuild speed?

I have a 750Gb 3-member software raid1 where 2 partitions are always 
present and the third is regularly rotated and re-synced (SATA disks in 
hot-swap bays).  The timing of the resync seems to be extremely variable 
recently, taking anywhere from 3 to 10 hours even if the partition is 
unmounted and the drives aren't doing anything else and regardless of 
what I echo into /proc/sys/dev/raid/speed_limit_min or _max.  Is there 
some way to tell if the drives are going bad or speed it up consistently 
if they aren't?
-- 
   Les Mikesell
    lesmikesell at gmail.com

Les Mikesell wrote:
> I have a 750Gb 3-member software raid1 where 2 partitions are always
present and the
> third is regularly rotated and re-synced (SATA disks in hot-swap bays). 
The timing of
> the resync seems to be extremely variable recently, taking anywhere from
3 to 10 hours
> even if the partition is unmounted and the drives aren't doing anything
else and
> regardless of what I echo into /proc/sys/dev/raid/speed_limit_min or
_max.  Is there
> some way to tell if the drives are going bad or speed it up consistently
if they aren't?

Only thing I can think is if there's a lot of activity on the disks, with
many, many gigs of files added or deleted.

          mark

On Wed, 2011-01-12 at 12:38 -0600, Les Mikesell wrote:
> I have a 750Gb 3-member software raid1 where 2 partitions are always 
> present and the third is regularly rotated and re-synced (SATA disks in 
> hot-swap bays).  The timing of the resync seems to be extremely variable 
> recently, taking anywhere from 3 to 10 hours even if the partition is 
> unmounted and the drives aren't doing anything else and regardless of 
> what I echo into /proc/sys/dev/raid/speed_limit_min or _max.  Is there 
> some way to tell if the drives are going bad or speed it up consistently 
> if they aren't?
echo 100000 > /proc/sys/dev/raid/speed_limit_min

echo 100000 > /proc/sys/dev/raid/speed_limit_max

Should equate to around 100MiBs and I suppose bad sectors or punctured
block will bring it to a crawl also.  Check the disk out with smart.  On
way to tell is keep a "hdparm" baseline.

John

On 12/01/2011 18:38, Les Mikesell wrote:
> I have a 750Gb 3-member software raid1 where 2 partitions are always
> present and the third is regularly rotated and re-synced (SATA disks in
> hot-swap bays).  The timing of the resync seems to be extremely variable
> recently, taking anywhere from 3 to 10 hours even if the partition is
> unmounted and the drives aren't doing anything else and regardless of
> what I echo into /proc/sys/dev/raid/speed_limit_min or _max.  Is there
> some way to tell if the drives are going bad or speed it up consistently
> if they aren't?
Ummmm.... RAID is not a backup policy. Fine use hotswap and rsync or 
similar but you
really shouldn't be relying on raid rebuilds for that.