Re: gluster volume + lvm : recommendation or neccessity ?

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2017-10-11 15:37 GMT+02:00 ML <lists@xxxxxxxxxxxxxxx>:
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_Storage/3/html/Administration_Guide/Formatting_and_Mounting_Bricks.html
http://gluster.readthedocs.io/en/latest/Administrator%20Guide/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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