[Lustre-discuss] help tracking down extremely high loads on OSSs

John White jwhite at lbl.gov
Mon Oct 18 11:58:04 PDT 2010


On Oct 18, 2010, at 10:49 AM, Peter Kjellstrom wrote:

> On Monday 18 October 2010, John White wrote:
>> Hello Folks,
>> 	A while back (say 3 weeks ago) we started noticing extremely high loads
>> (load avg around 300 at times) on our OSSs when in production and serving
>> IO.  This cluster was, at the time, on 1.8.2 (we have since upgraded to
>> 1.8.4 but the problem remains).  The load increases fairly predictably as
>> clients generate IO but even 2 clients can produce a load avg above 5.00. 
> 
> Does this impact performance or does it only show up as an unexpectedly high 
> number on the OSSes?

We have gotten reports of scaling issues that we had not experienced prior to this issue cropping up.  Throughput is certainly less predictable than before but we are able to hit the same peaks.

> 
> /Peter
> 
>> An identical file system of ours does not exhibit this behavior (sticks
>> below load avg 1.00 under even the heaviest IO load).  I've looked around
>> bugzilla and haven't found anything.  We've disabled heartbeat on the
>> off-chance that was generating the load (it's not), we've attempted using a
>> different client transport (o2ib->tcp), this did not solve the issue. 
>> There doesn't appear to be any specific non-kernel thread causing the
>> high-load.  The only info in dmesg/syslog pertains to sporadic client
>> evictions or sporadic slow setattr due to heavy IO load (we've since tuned
>> the number of OST threads).  We're basically out of ideas to try.
>> 
>> As reference, this is a 1 MDS/4 OSS cluster backed by a DDN 9900 couplet
>> (15 tiers, 1:1 lun mapping) running the lustre.org rpm build kernel for
>> 1.8.4.  The MDS/OSSs are Dell R710s and the MDT is a Dell MD1000.  Is this
>> a common problem or should a bug be filed?  Any info available upon
>> request.  Thanks for your time. ----------------
>> John White
>> High Performance Computing Services (HPCS)
>> (510) 486-7307
>> One Cyclotron Rd, MS: 50B-3209C
>> Lawrence Berkeley National Lab
>> Berkeley, CA 94720
> _______________________________________________
> Lustre-discuss mailing list
> Lustre-discuss at lists.lustre.org
> http://lists.lustre.org/mailman/listinfo/lustre-discuss

----------------
John White
High Performance Computing Services (HPCS)
(510) 486-7307
One Cyclotron Rd, MS: 50B-3209C
Lawrence Berkeley National Lab
Berkeley, CA 94720




More information about the lustre-discuss mailing list