[Users] which file system for shared disk?

Piotr Szubiakowski piotr.szubiakowski at nask.pl
Thu Jul 11 12:49:40 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.
It's great news for me!

Many thanks,
Piotr
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