Re: AMD64 System Becomes Unresponsive During Software RAID Synchronization

[Gabor Gombas <gombasg@sztaki.hu>]

On Mon, Oct 03, 2005 at 09:51:22AM -0400, Lennart Sorensen wrote:

> 2.6 kernels currently default to using up to 200M/s for resync.  This
> causes seriously painful disk access while this is taking place.
> 
> I personally always drop it to 10 or 15M/sec so that I can still work on
> the system while it syncs the raid.  This is done like this:
> 
> echo 10000 > /proc/sys/dev/raid/speed_limit_max
> 
> System becomes responsive again and the resync only takes about twice as
> long or so.  It certainly takes longer.

Have you tried using an other I/O scheduler (like cfq or deadline) on
the affected drives? According to my experiences, the default
anticipatory scheduler is very bad interactivity-wise when there is
heavy disk activity. On the other hand, anticipatory gives much better
throughput than cfq, so you have to decide what do you need.

Gabor

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     MTA SZTAKI Computer and Automation Research Institute
                Hungarian Academy of Sciences
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