[DRBD-user] Severe disk IO problems

Andreas Kurz andreas at hastexo.com
Fri Sep 6 14:48:43 CEST 2013

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

On 2013-08-30 19:31, Stephen Marsh wrote:
> Hi all,
> I've recently upgraded to DRBD 8.4.3 (protocol C) on CentOS 6.4 (kernel
> 3.10.10) with Xen 4.3.0 on hardware RAID10 with an Infiniband 20Gbit/sec
> replication link.
> For a few days now, we've been experiencing a very strange issue whereby
> (seemingly randomly) the system will become almost unresponsive, with
> iowait going to 100% on some (but not all) domUs and dom0, but even the
> domUs whose load remains stable will still be incredibly sluggish. The
> problem occurs even when the resources are in standalone mode.

One thing that I would check: if you are running the credit scheduler,
dom0 may have run out of credits. Check/increase credit scheduler domain
weights and make sure dom0 gets enough CPU time to serve i/o requests
...  explained here in the Xen wiki http://goo.gl/fqtS6Y


Need help with Linux-HA?

> Sometimes it self-corrects, but it's becoming more severe and is now
> less likely to go away without a reboot. Earlier today, the system
> running as primary was at 0.02 load, and the slave (which was doing
> nothing other than receiving updates from the master, no domUs running)
> went to 13 load and was pretty much dead.
> I've tried a variety of tuning options, including enabling
> disable_sendpage, but nothing is making it any better. Nothing is
> printed to the logs.
> My next thought is to try downgrading to DRBD 8.3, but considering
> support ends in December, I'd much prefer to continue using 8.4.
> I'm very much hoping that someone more experienced than myself will be
> able to offer some words of wisdom. :)
> Thanks
> Regards,
> Stephen Marsh
> _______________________________________________
> drbd-user mailing list
> drbd-user at lists.linbit.com
> http://lists.linbit.com/mailman/listinfo/drbd-user

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