Re: Raid reconstructing and process hanging in D state

[Justin Piszcz <jpiszcz@lucidpixels.com>]

On Fri, 16 Oct 2009, Holger Kiehl wrote:

> On Fri, 16 Oct 2009, Justin Piszcz wrote:
>> Hi,
>> 
>> I have the same problem with mdadm/raid-1, if you do not limit the speed in 
>> the speed_limit_min paramter, it will starve the I/O from all other 
>> processes and result in the same problem you are having.
>> 
> But in my case speed_limit_min was set to 1000 and speed_limit_max was 200000
> (ie. the default) and this still caused all process to hang in D-state. Only
> lowering speed_limit_max helped to make the system responsive again.
>
>> But for me I'm not sure about the reconstruction-- this happens for me 
>> during a raid verify/check.
>> 
> This was also the case for me, during a raid verify/check.
>
> Holger
>

Oops,

I meant the max speed has to be capped too.

Example, my old script (Velociraptors did 120MB/s) but anything over 
90MB/s it would start to starve the I/O;


# Set minimum and maximum raid rebuild speed to 30MB/s.
#echo "Setting maximum resync speed to 90 MiB/s..."
#echo 30000 > /sys/block/md0/md/sync_speed_min
#echo 90000 > /sys/block/md0/md/sync_speed_max

This would eat 90MB/s of the 120MB/s but still leave some breathing room.

Justin.