[Gluster-users] [ovirt-users] Ovirt/Gluster replica 3 distributed-replicated problem
Ravishankar N
ravishankar at redhat.com
Thu Sep 29 14:50:57 UTC 2016
On 09/29/2016 08:03 PM, Davide Ferrari wrote:
> It's strange, I've tried to trigger the error again by putting vm04 in
> maintenence and stopping the gluster service (from ovirt gui) and now
> the VM starts correctly. Maybe the arbiter indeed blamed the brick
> that was still up before, but how's that possible?
A write from the client on that file (vm image) could have succeeded
only on vm04 even before you brought it down.
> The only (maybe big) difference with the previous, erroneous
> situation, is that before I did maintenence (+ reboot) of 3 of my 4
> hosts, maybe I should have left more time between one reboot and another?
If you did not do anything from the previous run other than to bring the
node up and things worked, then the file is not in split-brain. Split
braine'd files need to be resolved before they can be accessed again,
which apparently did not happen in your case.
-Ravi
>
> 2016-09-29 14:16 GMT+02:00 Ravishankar N <ravishankar at redhat.com
> <mailto:ravishankar at redhat.com>>:
>
> On 09/29/2016 05:18 PM, Sahina Bose wrote:
>> Yes, this is a GlusterFS problem. Adding gluster users ML
>>
>> On Thu, Sep 29, 2016 at 5:11 PM, Davide Ferrari
>> <davide at billymob.com <mailto:davide at billymob.com>> wrote:
>>
>> Hello
>>
>> maybe this is more glustefs then ovirt related but since
>> OVirt integrates Gluster management and I'm experiencing the
>> problem in an ovirt cluster, I'm writing here.
>>
>> The problem is simple: I have a data domain mappend on a
>> replica 3 arbiter1 Gluster volume with 6 bricks, like this:
>>
>> Status of volume: data_ssd
>> Gluster process TCP Port RDMA Port Online Pid
>> ------------------------------------------------------------------------------
>> Brick vm01.storage.billy:/gluster/ssd/data/
>> brick 49153 0 Y 19298
>> Brick vm02.storage.billy:/gluster/ssd/data/
>> brick 49153 0 Y 6146
>> Brick vm03.storage.billy:/gluster/ssd/data/
>> arbiter_brick 49153 0 Y 6552
>> Brick vm03.storage.billy:/gluster/ssd/data/
>> brick 49154 0 Y 6559
>> Brick vm04.storage.billy:/gluster/ssd/data/
>> brick 49152 0 Y 6077
>> Brick vm02.storage.billy:/gluster/ssd/data/
>> arbiter_brick 49154 0 Y 6153
>> Self-heal Daemon on localhost N/A N/A
>> Y 30746
>> Self-heal Daemon on vm01.storage.billy N/A N/A
>> Y 196058
>> Self-heal Daemon on vm03.storage.billy N/A N/A
>> Y 23205
>> Self-heal Daemon on vm04.storage.billy N/A N/A
>> Y 8246
>>
>>
>> Now, I've put in maintenance the vm04 host, from ovirt,
>> ticking the "Stop gluster" checkbox, and Ovirt didn't
>> complain about anything. But when I tried to run a new VM it
>> complained about "storage I/O problem", while the storage
>> data status was always UP.
>>
>> Looking in the gluster logs I can see this:
>>
>> [2016-09-29 11:01:01.556908] I
>> [glusterfsd-mgmt.c:1596:mgmt_getspec_cbk] 0-glusterfs: No
>> change in volfile, continuing
>> [2016-09-29 11:02:28.124151] E [MSGID: 108008]
>> [afr-read-txn.c:89:afr_read_txn_refresh_done]
>> 0-data_ssd-replicate-1: Failing READ on gfid
>> bf5922b7-19f3-4ce3-98df-71e981ecca8d: split-brain observed.
>> [Input/output error]
>> [2016-09-29 11:02:28.126580] W [MSGID: 108008]
>> [afr-read-txn.c:244:afr_read_txn] 0-data_ssd-replicate-1:
>> Unreadable subvolume -1 found with event generation 6 for
>> gfid bf5922b7-19f3-4ce3-98df-71e981ecca8d. (Possible split-brain)
>> [2016-09-29 11:02:28.127374] E [MSGID: 108008]
>> [afr-read-txn.c:89:afr_read_txn_refresh_done]
>> 0-data_ssd-replicate-1: Failing FGETXATTR on gfid
>> bf5922b7-19f3-4ce3-98df-71e981ecca8d: split-brain observed.
>> [Input/output error]
>> [2016-09-29 11:02:28.128130] W [MSGID: 108027]
>> [afr-common.c:2403:afr_discover_done] 0-data_ssd-replicate-1:
>> no read subvols for (null)
>> [2016-09-29 11:02:28.129890] W
>> [fuse-bridge.c:2228:fuse_readv_cbk] 0-glusterfs-fuse: 8201:
>> READ => -1 gfid=bf5922b7-19f3-4ce3-98df-71e981ecca8d
>> fd=0x7f09b749d210 (Input/output error)
>> [2016-09-29 11:02:28.130824] E [MSGID: 108008]
>> [afr-read-txn.c:89:afr_read_txn_refresh_done]
>> 0-data_ssd-replicate-1: Failing FSTAT on gfid
>> bf5922b7-19f3-4ce3-98df-71e981ecca8d: split-brain observed.
>> [Input/output error]
>>
>
> Does `gluster volume heal data_ssd info split-brain` report that
> the file is in split-brain, with vm04 still being down?
> If yes, could you provide the extended attributes of this gfid
> from all 3 bricks:
> getfattr -d -m . -e hex
> /path/to/brick/bf/59/bf5922b7-19f3-4ce3-98df-71e981ecca8d
>
> If no, then I'm guessing that it is not in actual split-brain
> (hence the 'Possible split-brain' message). If the node you
> brought down contains the only good copy of the file (i.e the
> other data brick and arbiter are up, and the arbiter 'blames' this
> other brick), all I/O is failed with EIO to prevent file from
> getting into actual split-brain. The heals will happen when the
> good node comes up and I/O should be allowed again in that case.
>
> -Ravi
>
>
>> [2016-09-29 11:02:28.133879] W
>> [fuse-bridge.c:767:fuse_attr_cbk] 0-glusterfs-fuse: 8202:
>> FSTAT()
>> /ba2bd397-9222-424d-aecc-eb652c0169d9/images/f02ac1ce-52cd-4b81-8b29-f8006d0469e0/ff4e49c6-3084-4234-80a1-18a67615c527
>> => -1 (Input/output error)
>> The message "W [MSGID: 108008]
>> [afr-read-txn.c:244:afr_read_txn] 0-data_ssd-replicate-1:
>> Unreadable subvolume -1 found with event generation 6 for
>> gfid bf5922b7-19f3-4ce3-98df-71e981ecca8d. (Possible
>> split-brain)" repeated 11 times between [2016-09-29
>> 11:02:28.126580] and [2016-09-29 11:02:28.517744]
>> [2016-09-29 11:02:28.518607] E [MSGID: 108008]
>> [afr-read-txn.c:89:afr_read_txn_refresh_done]
>> 0-data_ssd-replicate-1: Failing STAT on gfid
>> bf5922b7-19f3-4ce3-98df-71e981ecca8d: split-brain observed.
>> [Input/output error]
>>
>> Now, how is it possible to have a split brain if I stopped
>> just ONE server which had just ONE of six bricks, and it was
>> cleanly shut down with maintenance mode from ovirt?
>>
>> I created the volume originally this way:
>> # gluster volume create data_ssd replica 3 arbiter 1
>> vm01.storage.billy:/gluster/ssd/data/brick
>> vm02.storage.billy:/gluster/ssd/data/brick
>> vm03.storage.billy:/gluster/ssd/data/arbiter_brick
>> vm03.storage.billy:/gluster/ssd/data/brick
>> vm04.storage.billy:/gluster/ssd/data/brick
>> vm02.storage.billy:/gluster/ssd/data/arbiter_brick
>> # gluster volume set data_ssd group virt
>> # gluster volume set data_ssd storage.owner-uid 36 && gluster
>> volume set data_ssd storage.owner-gid 36
>> # gluster volume start data_ssd
>>
>
>
>
>
>>
>>
>> --
>> Davide Ferrari
>> Senior Systems Engineer
>>
>> _______________________________________________
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>> Users at ovirt.org <mailto:Users at ovirt.org>
>> http://lists.ovirt.org/mailman/listinfo/users
>> <http://lists.ovirt.org/mailman/listinfo/users>
>>
>>
>
>
>
>
> --
> Davide Ferrari
> Senior Systems Engineer
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