[Lustre-discuss] Frequent OSS Crashes with heavy load

Andreas Dilger adilger at sun.com
Wed Nov 12 09:36:33 PST 2008


On Nov 12, 2008  13:48 +0000, Wang lu wrote:
> May I ask where can I run PIOS command? I think to determine the max thread
> number of OSS, it should be run on OSS, however, the OST directorys are
> unwritable. Can I write to /dev/sdaX? I am confused. 

Running PIOS directly the /dev/sdX will overwrite all data there.  It should
only be run on the disk devices before the filesystem is formatted.  You
can run PIOS against the filesystem itself (e.g. /mnt/lustre) to just create
regular files in the filesystem.

> Brian J. Murrell 写:
> 
> > On Mon, 2008-11-10 at 16:42 +0000, Wang lu wrote:
> >> I have already 512(max number) IO thread running. Some of them are of "Dead"
> >> status. Is it safe to draw conclusion that the OSS is oversubscribed? 
> > 
> > Until you do some analysis of your storage with the iokit, one cannot
> > really draw any conclusions, however if you are already at the maximum
> > value of OST threads, it would not be difficult to believe that perhaps
> > this is a possibility.
> > 
> > Try a simple experiment and half the number to 256 and see if you have
> > any drop off in throughput to the storage devices.  If not, then you can
> > easily assume that 512 was either too much or not necessary.  You can
> > try doing this again if you wish.  If you get to a value of OST threads
> > where your throughput is lower than it should be, you've gone too low.
> > 
> > But really, the iokit is the more efficient and accurate way to
> > determine this.
> > 
> > b.
> > 
> 
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Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.




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