Re: Ceph Ansible Repo

[David McBride <dwm37@cam.ac.uk>]

On 06/03/14 13:19, Gandalf Corvotempesta wrote:
> 2014-03-06 13:07 GMT+01:00 David McBride <dwm37@cam.ac.uk>:
>> This causes the IO load to be nicely balanced across the two SSDs,
>> removing any hot spots, at the cost of enlarging the failure domain of
>> the loss of an SSD from half a node to a full node.
> 
> This is not a solution for me.
> Why not using LVM with a VG striped across both SSD ?
> I've never used LVM without raid, what happens in case of failure
> of a phisical disks?  The whole VG is lost ?

Yes.  A stripe-set depends on all of the members of an array, whether
managed through MD or LVM.

Thus, in a machine with two SSDs, which are striped together, the loss
of *either* SSD will cause all of the OSDs hosted by that machine to be
lost.

(Note: if you want to use LVM rather than GPTs on MD, you will probably
need to remove the '|dm-*' clause from the Ceph udev rules that govern
OSD assembly before they will work as expected.)

Kind regards,
David
-- 
David McBride <dwm37@cam.ac.uk>
Unix Specialist, University Computing Service