Re: Software RAID level 1 issue

[Paul Clements <Paul.Clements@SteelEye.com>]

3tcdgwg3 wrote:
 
> If there is a plan to do a "intelligent resync", like some of the raid
> controller
> vendors offer?  The resync process will be hold on, if there are IO requests
> from upper level, and resumed when there is no IO.  By doing that, the
> system
> performance always be on the top.  I am very interested in  having something
> like that.

This wasn't exactly what I meant by intelligent resync, but...I think
what you're asking about is something that the md driver already does to
some extent. It will slow down a resync if there is active I/O on the
device. This can even be tuned by the user by manipulating a couple of
kernel sysctls: 

apache:~# cat /proc/sys/dev/raid/speed_limit_min 
100

apache:~# cat /proc/sys/dev/raid/speed_limit_max 
10000

apache:~# echo 1000000 > /proc/sys/dev/raid/speed_limit_max

apache:~# cat /proc/sys/dev/raid/speed_limit_max
1000000


These are in KB/s. 

The "min" refers to the maximum I/O bandwidth that will be consumed by
resyncs before the resyncs get throttled, when there is other I/O
activity on the device.

The "max" refers to the maximum I/O bandwidth that will be consumed by
resyncs before the resyncs get throttled, even if there is no other I/O
activity on the device.

--
Paul