[BlueOnyx:07984] Re: Software RAID rebuild faster

[Richard Morgan]

This did and does help rather a lot...

While RAID is rebuilding I ran:

echo 195000 > /proc/sys/dev/raid/speed_limit_min

This shaved about an hour off an estimated four hour rebuild time.  I 
fiddled around with stopping apache, mysql, etc.  This hardly made any 
difference, but then the server is fairly quiet anyway... maybe a busy 
server would have seen a significant difference.

Many thanks for sharing your knowledge.

Richard

----- Original Message ----- 
From: "Christoph Schneeberger" <cschnee at box.telemedia.ch>
To: "BlueOnyx General Mailing List" <blueonyx at mail.blueonyx.it>
Sent: Saturday, July 30, 2011 11:50 AM
Subject: [BlueOnyx:07920] Re: Software RAID rebuild faster


> Generally said, make sure that only little or even better no writes and
> reads happen during sync (shutdown daemons and processes if you can
> afford it).
> Most probably the underlying hardware speed is your bottleneck, but you
> can play with the following 2 parameters to see if you can speed up the
> syncing a bit (they do what you actually tried with renicing):
>
> /proc/sys/dev/raid/speed_limit_max
> /proc/sys/dev/raid/speed_limit_min
>
> In most cases they are set as 200000 and 1000 respectively. Upping the
> max won't help much, but upping the min value can speed things quite a 
> bit.
>
> HTHTH*,
> Christoph
>
> * HopeThisHelpsTheHoping
>
>
> Richard Morgan wrote:
>> Hi, hope someone can help...
>>
>> I have to go to the data centre tomorrow (a two hour drive each
>> way) to swap a failed disk - my tests and experience make me
>> think that the RAID1 rebuild will take about five hours for the 1TB
>> disks.  As I also want to replace the current good disk with a new one
>> it means waiting for the rebuild to complete.
>>
>> Is there anyway to speed this up?  I've experimented with 'top' then
>> 'r' for renice - changing it to -15 or -20, etc.  It doesn't make much
>> difference.  I was wondering if there was anything else I could do
>> even if the server is offline for a while.
>>
>> Here's hoping :o), Richard
>
>
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