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.
––––
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Cloud Engineer
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On 06 Mar 2014, at 14:28, David McBride <[email protected]> wrote:
> On 06/03/14 13:19, Gandalf Corvotempesta wrote:
>> 2014-03-06 13:07 GMT+01:00 David McBride <[email protected]>:
>>> 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 <[email protected]>
> Unix Specialist, University Computing Service
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