Re: high cpu load with sw raid1

Andreas Dilger (adilger@turbolabs.com)
Fri, 21 Sep 2001 02:09:38 -0600


On Sep 21, 2001 09:07 +0200, David Hajek wrote:
> On Thu, Sep 20, 2001, Andreas Dilger wrote:
> > On Sep 20, 2001 10:26 +0200, David Hajek wrote:
> > > I have linux box with 70GB SW Raid1. This box runs for half
> > > a year without problems but now I meet the high cpu load
> > > problems. I suspect that it can be caused by not enough
> > > free disk space on this md device. I see following:
> > >
> > > 1 GB free - load > 5
> > > 5 GB free - load < 1
> >
> > What filesystem are you using? If it is reiserfs, and you have < 10%
> > of the disk free, it is very unhappy. A patch to fix this is available.
>
> I'm using ext2. I suspect high ext2 fragmentation, because when
> there are 'only' 1GB free the disk is _really_ busy. I doubt
> that it takes lot of time to find free blocks.

OK, I just re-read your initial posting, and see you have a 70GB RAID,
so 1GB free is about 1.4% free, which makes for bad performance no
matter what filesystem you have. In general, ext2 will have this 1%
free space spread evenly across all of the disk, so while 1GB is still
a lot of space, it is still a nearly full filesystem.

Cheers, Andreas

--
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert

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