Gluster users - Feb 2017 - lvm layout for gluster -- using multiple physical volumes

Hi all,

I want to use lvm for two reasons:

- gluster snaphosts
- ability to dynamically add space to a brick.


Here's what i'd like to do:

1. create two more physical volumes
2. create a single volume group from those physical volumes
3. create a single logical volume
4. make the single logical volume a brick

So my questions are this:

1. is there any issue with adding and remove LVM physical volumes from the
logical volume group that backs the gluster brick?
2. is there any issue with having multiple physical volumes in the LVM
volume group?
3. will disk size increase more  with gluster because LVM is being used
instead a filesystem like XFS?

Thanks,
Joe
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On Fri, Feb 10, 2017 at 10:30 PM, Joseph Lorenzini <jaloren at gmail.com>
wrote:
> Hi all,
>
> I want to use lvm for two reasons:
>
> - gluster snaphosts
> - ability to dynamically add space to a brick.
>
>
> Here's what i'd like to do:
>
> 1. create two more physical volumes
> 2. create a single volume group from those physical volumes
> 3. create a single logical volume
> 4. make the single logical volume a brick
>
> So my questions are this:
>
> 1. is there any issue with adding and remove LVM physical volumes from the
> logical volume group that backs the gluster brick?
I don't see any issue in adding PV to a VG, but without data migration
you cannot
remove a PV from an VG. Unless the PV is not in use.
> 2. is there any issue with having multiple physical volumes in the LVM
> volume group?
AFAIK there is no issues in having multiple PV in a VG.
> 3. will disk size increase more  with gluster because LVM is being used
> instead a filesystem like XFS?
I am not sure what you are asking here.

You will still need a filesystem on top of a LV. So with additional
LVM metadata your total
usable disk size will decrease a little.

I believe you are planning to use thin provisioning because Gluster
snapshots work only with that.
In that case you can create a larger LV (larger than your VG) and when
your pool utilization increase
you can add more space to VG by adding PVs. Otherwise everytime you
increase your VG size and LV
size you have to extend the filesystem as well.

Regards,
Rajesh