[Xen-users] RE: Concurrent local write error in DRBD with GPL PV drivers

[Philippe Lang <philippe.lang@xxxxxxxxxxxxxx>]

Hi,

There's was no answer to my post of last week. Does anyone know how to contact 
directly the maintainers of the GPL PV driver maybe?

Before starting using our new servers in production, we'd like to know if the 
drbd error mentioned is not problem at all, or if we have better wait until 
this case is being investigated.

One more precision: we use Debian Lenny for the dom0 OS.

Best regards,

-------------------------------------------------------------
Attik System              web  : http://www.attiksystem.ch
Philippe Lang             phone: +41 26 422 13 75
rte de la Fonderie 2      gsm  : +41 79 351 49 94
1700 Fribourg             pgp  : http://keyserver.pgp.com 


> -----Message d'origine-----
> DeÂ: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-
> bounces@xxxxxxxxxxxxxxxxxxx] De la part de Philippe Lang
> EnvoyÃÂ: vendredi 7 mai 2010 10:33
> ÃÂ: xen-users@xxxxxxxxxxxxxxxxxxx
> ObjetÂ: [Xen-users] Concurrent local write error in DRBD with GPL PV
> drivers
> 
> Hi,
> 
> We are about to start using in production Windows 2003 64bits XEN VMs
> running on top of a DRBD cluster. We have installed the latest GPL PV
> optimized drivers. (gplpv_2003x64_0.11.0.213.msi)
> 
> Sometimes, when the VM writes on disk, we can see the following error
> in the DRBD log:
> 
> May  6 17:45:48 s3 kernel: [198887.626841] drbd0: blkback.35.hda[3549]
> Concurrent local write detected! [DISCARD L] new: 26745079s +4096;
> pending: 26745079s +4096
> 
> This error is discussed in the following thread of the DRBD mailing
> list:
> 
> http://lists.linbit.com/pipermail/drbd-user/2009-April/011873.html
> 
> Basically, it is due to the fact that a write occurs at a specific
> location, while another "in-flight" write is taking place at the same
> location. In order to avoid a cluster desynchronization, DRBD drops the
> second write.
> 
> We were able to reproduce this problem, with the help of a Windows
> program called "PerformanceTest" from Passmark Software. When doing a
> "Disk Random Seek +RW" test, the logs gets filled with the error
> mentioned at the top of this message.
> 
> We have tested a VM *without* the gplpv drivers, and *no error*
> appears. We have tested previous drivers versions (0.11.0.188,
> 0.10.0.142), and the same error appears.
> 
> So, we have the feeling there is some kind of error in the driver,
> although we have never experienced a single VM crash. Can we safely
> ignore the "Concurrent local write error" mentioned in the log, or is
> that really a bug that should be corrected before using the driver in
> production?
> 
> Best regards,
> 
> -------------------------------------------------------------
> Attik System              web  : http://www.attiksystem.ch
> Philippe Lang             phone: +41 26 422 13 75
> rte de la Fonderie 2      gsm  : +41 79 351 49 94
> 1700 Fribourg             pgp  : http://keyserver.pgp.com

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