[Gluster-devel] Physical HDD unplug test

[qingwei wei]

Hi,

I updated my client to 3.7.14 and i no longer experience split-brain
error. It seems like there is some changes on the client side that fix
this error. Please note that, for this test, i still stick to 3.7.10
server. Will it be an issue with client and server using different
version?

Cw

On Tue, Aug 16, 2016 at 5:46 PM, Krutika Dhananjay <kdhananj at redhat.com> wrote:
> 3.7.11 had quite a few bugs in afr and sharding+afr interop that were fixed
> in 3.7.12.
> Some of them were about files being reported as being in split-brain.
> Chances are that some of them existed in 3.7.10 as well - which is what
> you're using.
>
> Do you mind trying the same test with 3.7.12 or a later version?
>
> -Krutika
>
> On Tue, Aug 16, 2016 at 2:46 PM, qingwei wei <tchengwee at gmail.com> wrote:
>>
>> Hi Niels,
>>
>> My situation is that when i unplug the HDD physically, the FIO
>> application exits with Input/Output error. However, when i do echo
>> offline on the disk, the FIO application does freeze a bit but still
>> manage to resume the IO workload after the freeze.
>>
>> From what i can see from the client log, the error is split-brain
>> which does not make sense as i still have 2 working replicas.
>>
>> [2016-08-12 10:33:41.854283] E [MSGID:
>> 108008][afr-transaction.c:1989:afr_transaction]
>> 0-ad17hwssd7-replicate-0:
>> Failing WRITE on gfid 665a43df-1ece-4c9a-a6ee-fcfa960d95bf:split-brain
>> observed. [Input/output error]
>>
>> So anyone can share their testing experience on this type disruptive
>> test on shard volume? Thanks!
>>
>> Regards,
>>
>> Cheng Wee
>>
>> On Tue, Aug 16, 2016 at 4:45 PM, Niels de Vos <ndevos at redhat.com> wrote:
>> > On Tue, Aug 16, 2016 at 01:34:36PM +0800, qingwei wei wrote:
>> >> Hi,
>> >>
>> >> I am currently trying to test the distributed replica (3 replicas)
>> >> reliability when 1 brick is down. I tried using both software unplug
>> >> method by issuing the exho offline > /sys/block/sdx/device/state and
>> >> also physically unplug the HDD and i encountered 2 different outcomes.
>> >> For software unplug, the FIO workload continue to run but for
>> >> physically unplug the HDD, FIO workload cannot continue with the
>> >> following error:
>> >>
>> >> [2016-08-12 10:33:41.854283] E [MSGID: 108008]
>> >> [afr-transaction.c:1989:afr_transaction] 0-ad17hwssd7-replicate-0:
>> >> Failing WRITE on gfid 665a43df-1ece-4c9a-a6ee-fcfa960d95bf:
>> >> split-brain observed. [Input/output error]
>> >>
>> >> From the server where i unplug the disk, i can see the following:
>> >>
>> >> [2016-08-12 10:33:41.916456] D [MSGID: 0]
>> >> [io-threads.c:351:iot_schedule] 0-ad17hwssd7-io-threads: LOOKUP
>> >> scheduled as fast fop
>> >> [2016-08-12 10:33:41.916666] D [MSGID: 115050]
>> >> [server-rpc-fops.c:179:server_lookup_cbk] 0-ad17hwssd7-server: 8127:
>> >> LOOKUP /.shard/150e99ee-ce3b-4b57-8c40-99b4ecdf3822.90
>> >>
>> >> (be318638-e8a0-4c6d-977d-7a937aa84806/150e99ee-ce3b-4b57-8c40-99b4ecdf3822.90)
>> >> ==> (No such file or directory) [No such file or directory]
>> >> [2016-08-12 10:33:41.916804] D [MSGID: 101171]
>> >> [client_t.c:417:gf_client_unref] 0-client_t:
>> >>
>> >> hp.dctopenstack.org-25780-2016/08/12-10:33:07:589960-ad17hwssd7-client-0-0-0:
>> >> ref-count 1
>> >> [2016-08-12 10:33:41.917098] D [MSGID: 101171]
>> >> [client_t.c:333:gf_client_ref] 0-client_t:
>> >>
>> >> hp.dctopenstack.org-25780-2016/08/12-10:33:07:589960-ad17hwssd7-client-0-0-0:
>> >> ref-count 2
>> >> [2016-08-12 10:33:41.917145] W [MSGID: 115009]
>> >> [server-resolve.c:571:server_resolve] 0-ad17hwssd7-server: no
>> >> resolution type for (null) (LOOKUP)
>> >> [2016-08-12 10:33:41.917182] E [MSGID: 115050]
>> >> [server-rpc-fops.c:179:server_lookup_cbk] 0-ad17hwssd7-server: 8128:
>> >> LOOKUP (null)
>> >> (00000000-0000-0000-0000-000000000000/150e99ee-ce3b-4b57-8c40-99b4ecdf3822.90)
>> >> ==> (Invalid argument) [Invalid argument]
>> >>
>> >> I am using gluster 3.7.10 and the configuration is as follow:
>> >>
>> >> diagnostics.brick-log-level: DEBUG
>> >> diagnostics.client-log-level: DEBUG
>> >> performance.io-thread-count: 16
>> >> client.event-threads: 2
>> >> server.event-threads: 2
>> >> features.shard-block-size: 16MB
>> >> features.shard: on
>> >> server.allow-insecure: on
>> >> storage.owner-uid: 165
>> >> storage.owner-gid: 165
>> >> nfs.disable: true
>> >> performance.quick-read: off
>> >> performance.io-cache: off
>> >> performance.read-ahead: off
>> >> performance.stat-prefetch: off
>> >> cluster.lookup-optimize: on
>> >> cluster.quorum-type: auto
>> >> cluster.server-quorum-type: server
>> >> transport.address-family: inet
>> >> performance.readdir-ahead: on
>> >>
>> >> This error only occur for sharding configuration. Do you guys perform
>> >> this type of test before? Or do you think physically unplug the HDD is
>> >> a valid test case?
>> >
>> > If you use replica-3, things should settle down again. The kernel and
>> > teh brick process needs a little time to find out that the filesystem on
>> > the disk that you pulled out is not responding anymore. The output og
>> > "gluster volume status" should show that the brick process is offline.
>> > As long as you have quorum, things should continue after a small delay
>> > while waiting to mark the brick offline.
>> >
>> > People actually should test this scenario, it can be that power to disks
>> > fail, or even (connections to) RAID-controllers. Hot-unplugging is
>> > definitely a scenario that can emulate real-world problems.
>> >
>> > Niels
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