I believe there is a use case behind the lvm journals. For instance you can do: 2 SSDs: * tiny mdadm raid 1 setup for the system; let’s say /dev/sda1 and /dev/sdb1 * then you still have: * /dev/sda2 * /dev/sdb2 They can both host journals, and you usually want to manage them with lvm, this is easier than managing partition. I just open an issue as a feature/enhancement request. https://github.com/ceph/ceph-ansible/issues/9 This shouldn’t be that difficult to implement. –––– Sébastien Han Cloud Engineer "Always give 100%. Unless you're giving blood.” Phone: +33 (0)1 49 70 99 72 Mail: sebastien.han@xxxxxxxxxxxx Address : 11 bis, rue Roquépine - 75008 Paris Web : www.enovance.com - Twitter : @enovance On 06 Mar 2014, at 14:28, David McBride <dwm37@xxxxxxxxx> wrote: > On 06/03/14 13:19, Gandalf Corvotempesta wrote: >> 2014-03-06 13:07 GMT+01:00 David McBride <dwm37@xxxxxxxxx>: >>> 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@xxxxxxxxx> > Unix Specialist, University Computing Service
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