[Users] which file system for shared disk?

Yuriy Demchenko demchenko.ya at gmail.com
Thu Jul 11 10:58:09 UTC 2013


On 07/11/2013 02:45 PM, Piotr Szubiakowski wrote:
>
>
>> On 07/11/2013 12:52 PM, Piotr Szubiakowski wrote:
>>>
>>>>> The way that oVirt manage storage domains accessed via FC is very 
>>>>> smart.
>>>>> There is separate logical volume for each virtual disk. But I 
>>>>> think that
>>>>> logical volume at the same time could be "touched" only by one 
>>>>> host. Is
>>>>> it possible that two host access read/write the same logical 
>>>>> volume and
>>>>> there is no data corruption?
>>>>
>>>> hence a shared disk over block storage using LVM must be 
>>>> pre-allocated, so no LV changes (lv extend) would be needed.
>>>> (also, it cannot have snapshots, since it would become qcow)
>>>
>>> Ok, but this is the hypervisor view. For a guest OS this LV is 
>>> normal RAW block device. I wonder if someone test this feature and 
>>> access shared disk from many VM's at the same time?
>> I did a brief tests - 3 vms, shared disk, cman/pacemaker + gfs2 - had 
>> no problems using it, no data corruption. although that was only 
>> basic tests, like create/move/delete files, no extensive usage/stress 
>> or something like that.
>
> Thanks Yuri,
> Is fencing handled by the cman/pacemaker? I read about the fanced 
> daemon and it seems to be difficult to use it together with oVirt.
>
> Piotr
yea, fencing handled by pacemaker, stonith resource fence_rhev - 
parameters according to man page, with one exception - had to add 
/pcmk_host_list="vmname" /additional parameter, so pacemaker would know 
that this stonith device belongs to that VM.
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