Gluster users - May 2017 - VM going down

Niels,

Allesandro's configuration does not have shard enabled. So it has
definitely not got anything to do with shard not supporting seek fop.

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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Il 11/05/2017 09:05, Krutika Dhananjay ha scritto:
> Niels,
>
> Allesandro's configuration does not have shard enabled. So it has
> definitely not got anything to do with shard not supporting seek fop.
>
> Copy-pasting volume-info output from the first mail:
>
Hi,
I know sharding is not enabled, I had the impression it's not stable
enough to be used yet.

Beside that as said the seek error is triggered when the VM is started
up not when it's suddenly stopped.

Though the problem still persists, yesterday I had a new down of one VM.

My next step will be to start qemu with debugging to see where it
crashes (or if it shutsdown by itself for some reasons)

If anybody has any other hint I would greatly appreciate.
If needed I might provide all the /var/log of the host/s.

Alessandro

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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