[Gluster-users] VM going down

Niels de Vos
Thu, 11 May 2017 12:09:46 -0000

On Thu, May 11, 2017 at 12:35:42PM +0530, Krutika Dhananjay
wrote:
> Niels,
>
> Allesandro's configuration does not have shard enabled. So it has
> definitely not got anything to do with shard not supporting seek fop.

Yes, but in case sharding would have been enabled, the seek FOP would be
handled correctly (detected as not supported at all).

I'm still not sure how arbiter prevents doing shards though. We normally
advise to use sharding *and* (optional) arbiter for VM workloads,
arbiter without sharding has not been tested much. In addition, the seek
functionality is only available in recent kernels, so there has been
little testing on CentOS or similar enterprise Linux distributions.

HTH,
Niels


> Copy-pasting volume-info output from the first mail:
>
> Volume Name: datastore2
> Type: Replicate
> Volume ID: c95ebb5f-6e04-4f09-91b9-bbbe63d83aea
> Status: Started
> Snapshot Count: 0
> Number of Bricks: 1 x (2 + 1) = 3
> Transport-type: tcp
> Bricks:
> Brick1: srvpve2g:/data/brick2/brick
> Brick2: srvpve3g:/data/brick2/brick
> Brick3: srvpve1g:/data/brick2/brick (arbiter)
> Options Reconfigured:
> nfs.disable: on
> performance.readdir-ahead: on
> transport.address-family: inet
>
>
> -Krutika
>
>
> On Tue, May 9, 2017 at 7:40 PM, Niels de Vos <ndevos at redhat.com>
wrote:
>
> > ...
> > > > client from
> > > >
srvpve2-162483-2017/05/08-10:01:06:189720-datastore2-client-0-0-0
> > > > (version: 3.8.11)
> > > > [2017-05-08 10:01:06.237433] E [MSGID: 113107]
> > [posix.c:1079:posix_seek]
> > > > 0-datastore2-posix: seek failed on fd 18 length 42957209600
[No such
> > > > device or address]
> >
> > The SEEK procedure translates to lseek() in the posix xlator. This can
> > return with "No suck device or address" (ENXIO) in only one
case:
> >
> >     ENXIO    whence is SEEK_DATA or SEEK_HOLE, and the file offset is
> >              beyond the end of the file.
> >
> > This means that an lseek() was executed where the current offset of
the
> > filedescriptor was higher than the size of the file. I'm not sure
how
> > that could happen... Sharding prevents using SEEK at all atm.
> >
> > ...
> > > > The strange part is that I cannot seem to find any other
error.
> > > > If I restart the VM everything works as expected (it stopped
at ~9.51
> > > > UTC and was started at ~10.01 UTC) .
> > > >
> > > > This is not the first time that this happened, and I do not
see any
> > > > problems with networking or the hosts.
> > > >
> > > > Gluster version is 3.8.11
> > > > this is the incriminated volume (though it happened on a
different one
> > too)
> > > >
> > > > Volume Name: datastore2
> > > > Type: Replicate
> > > > Volume ID: c95ebb5f-6e04-4f09-91b9-bbbe63d83aea
> > > > Status: Started
> > > > Snapshot Count: 0
> > > > Number of Bricks: 1 x (2 + 1) = 3
> > > > Transport-type: tcp
> > > > Bricks:
> > > > Brick1: srvpve2g:/data/brick2/brick
> > > > Brick2: srvpve3g:/data/brick2/brick
> > > > Brick3: srvpve1g:/data/brick2/brick (arbiter)
> > > > Options Reconfigured:
> > > > nfs.disable: on
> > > > performance.readdir-ahead: on
> > > > transport.address-family: inet
> > > >
> > > > Any hint on how to dig more deeply into the reason would be
greatly
> > > > appreciated.
> >
> > Probably the problem is with SEEK support in the arbiter
functionality.
> > Just like with a READ or a WRITE on the arbiter brick, SEEK can only
> > succeed on bricks where the files with content are located. It does
not
> > look like arbiter handles SEEK, so the offset in lseek() will likely
be
> > higher than the size of the file on the brick (empty, 0 size file). I
> > don't know how the replication xlator responds on an error return
from
> > SEEK on one of the bricks, but I doubt it likes it.
> >
> > We have https://bugzilla.redhat.com/show_bug.cgi?id=1301647 to support
> > SEEK for sharding. I suggest you open a bug for getting SEEK in the
> > arbiter xlator as well.
> >
> > HTH,
> > Niels
> >
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