[Gluster-users] gluster volume + lvm : recommendation or neccessity ?

[Ivan Rossi]

2017-10-11 15:37 GMT+02:00 ML <lists at websiteburo.com>:

> After some extra reading about LVM snapshots & Gluster, I think I can
> conclude it may be a bad idea to use it on big storage bricks.
>
> I understood that the LVM maximum metadata, used to store the snapshots
> data, is about 16GB.
>

LVM metadata  aer used to store changed METADATA, not data.
thin-provisioned snapshots usually may grow up to the local unallocated
capacity.


> So if I have a brick with a volume arount 10TB (for example), daily
> snapshots, files changing ~100GB : the LVM snapshot is useless.
>
> LVM's snapshots doesn't seems to be a good idea with very big LVM
> partitions.
>
> Did I missed something ? Hard to find clear documentation on the subject.
>

LVM documentation (RH has very good docs available via web) and even the
lvcreate man page is OK. not a lightweight read but OK. You need
thin-provisioned lvm pools to have snapshots in gluster.


>
> Le 11/10/2017 à 09:07, Ric Wheeler a écrit :
>
>> On 10/11/2017 09:50 AM, ML wrote:
>>
>>> Hi everyone,
>>>
>>> I've read on the gluster & redhat documentation, that it seems
>>> recommended to use XFS over LVM before creating & using gluster volumes.
>>>
>>> Sources :
>>> https://access.redhat.com/documentation/en-US/Red_Hat_Storag
>>> e/3/html/Administration_Guide/Formatting_and_Mounting_Bricks.html
>>> http://gluster.readthedocs.io/en/latest/Administrator%20Guid
>>> e/Setting%20Up%20Volumes/
>>>
>>> My point is : do we really need LVM ?
>>> For example , on a dedicated server with disks & partitions that will
>>> not change of size, it doesn't seems necessary to use LVM.
>>>
>>> I can't understand clearly wich partitioning strategy would be the best
>>> for "static size" hard drives :
>>>
>>> 1 LVM+XFS partition = multiple gluster volumes
>>> or 1 LVM+XFS partition = 1 gluster volume per LVM+XFS partition
>>> or 1 XFS partition = multiple gluster volumes
>>> or 1 XFS partition = 1 gluster volume per XFS partition
>>>
>>> What do you use on your servers ?
>>>
>>> Thanks for your help! :)
>>>
>>> Quentin
>>>
>>
>> Hi Quentin,
>>
>> Gluster relies on LVM for snapshots - you won't get those unless you
>> deploy on LVM.
>>
>> Regards,
>> Ric
>>
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>
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