[Gluster-users] corruption using gluster and iSCSI with LIO

[Olivier Lambert]

Okay, used the exact same config you provided, and adding an arbiter
node (node3)

After halting node2, VM continues to work after a small "lag"/freeze.
I restarted node2 and it was back online: OK

Then, after waiting few minutes, halting node1. And **just** at this
moment, the VM is corrupted (segmentation fault, /var/log folder empty
etc.)

dmesg of the VM:

[ 1645.852905] EXT4-fs error (device xvda1):
htree_dirblock_to_tree:988: inode #19: block 8286: comm bash: bad
entry in directory: rec_len is smaller than minimal - offset=0(0),
inode=0, rec_len=0, name_len=0
[ 1645.854509] Aborting journal on device xvda1-8.
[ 1645.855524] EXT4-fs (xvda1): Remounting filesystem read-only

And got a lot of " comm bash: bad entry in directory" messages then...

Here is the current config with all Node back online:

# gluster volume info

Volume Name: gv0
Type: Replicate
Volume ID: 5f15c919-57e3-4648-b20a-395d9fe3d7d6
Status: Started
Snapshot Count: 0
Number of Bricks: 1 x (2 + 1) = 3
Transport-type: tcp
Bricks:
Brick1: 10.0.0.1:/bricks/brick1/gv0
Brick2: 10.0.0.2:/bricks/brick1/gv0
Brick3: 10.0.0.3:/bricks/brick1/gv0 (arbiter)
Options Reconfigured:
nfs.disable: on
performance.readdir-ahead: on
transport.address-family: inet
features.shard: on
features.shard-block-size: 16MB
network.remote-dio: enable
cluster.eager-lock: enable
performance.io-cache: off
performance.read-ahead: off
performance.quick-read: off
performance.stat-prefetch: on
performance.strict-write-ordering: off
cluster.server-quorum-type: server
cluster.quorum-type: auto
cluster.data-self-heal: on


# gluster volume status
Status of volume: gv0
Gluster process                             TCP Port  RDMA Port  Online  Pid
------------------------------------------------------------------------------
Brick 10.0.0.1:/bricks/brick1/gv0           49152     0          Y       1331
Brick 10.0.0.2:/bricks/brick1/gv0           49152     0          Y       2274
Brick 10.0.0.3:/bricks/brick1/gv0           49152     0          Y       2355
Self-heal Daemon on localhost               N/A       N/A        Y       2300
Self-heal Daemon on 10.0.0.3                N/A       N/A        Y       10530
Self-heal Daemon on 10.0.0.2                N/A       N/A        Y       2425

Task Status of Volume gv0
------------------------------------------------------------------------------
There are no active volume tasks



On Thu, Nov 17, 2016 at 11:35 PM, Olivier Lambert
<lambert.olivier at gmail.com> wrote:
> It's planned to have an arbiter soon :) It was just preliminary tests.
>
> Thanks for the settings, I'll test this soon and I'll come back to you!
>
> On Thu, Nov 17, 2016 at 11:29 PM, Lindsay Mathieson
> <lindsay.mathieson at gmail.com> wrote:
>> On 18/11/2016 8:17 AM, Olivier Lambert wrote:
>>>
>>> gluster volume info gv0
>>>
>>> Volume Name: gv0
>>> Type: Replicate
>>> Volume ID: 2f8658ed-0d9d-4a6f-a00b-96e9d3470b53
>>> Status: Started
>>> Snapshot Count: 0
>>> Number of Bricks: 1 x 2 = 2
>>> Transport-type: tcp
>>> Bricks:
>>> Brick1: 10.0.0.1:/bricks/brick1/gv0
>>> Brick2: 10.0.0.2:/bricks/brick1/gv0
>>> Options Reconfigured:
>>> nfs.disable: on
>>> performance.readdir-ahead: on
>>> transport.address-family: inet
>>> features.shard: on
>>> features.shard-block-size: 16MB
>>
>>
>>
>> When hosting VM's its essential to set these options:
>>
>> network.remote-dio: enable
>> cluster.eager-lock: enable
>> performance.io-cache: off
>> performance.read-ahead: off
>> performance.quick-read: off
>> performance.stat-prefetch: on
>> performance.strict-write-ordering: off
>> cluster.server-quorum-type: server
>> cluster.quorum-type: auto
>> cluster.data-self-heal: on
>>
>> Also with replica two and quorum on (required) your volume will become
>> read-only when one node goes down to prevent the possibility of split-brain
>> - you *really* want to avoid that :)
>>
>> I'd recommend a replica 3 volume, that way 1 node can go down, but the other
>> two still form a quorum and will remain r/w.
>>
>> If the extra disks are not possible, then a Arbiter volume can be setup -
>> basically dummy files on the third node.
>>
>>
>>
>> --
>> Lindsay Mathieson
>>
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