I think this would be a great place in the ML to look. https://ceph-users.ceph.narkive.com/AthYx879/ceph-volume-migration-and-disk-... <https://ceph-users.ceph.narkive.com/AthYx879/ceph-volume-migration-and-disk-partition-support> Reed
On Mar 19, 2021, at 2:17 PM, Marc <Marc@f1-outsourcing.eu> wrote:
I have asked exactly the same question 1 year ago or so. Sage told me to show evidence of a significant impact, because they did not measured one.
If I remember correctly is the idea behind this that not all storage devices are available as /dev/sdX as normal disk and lvm sort of solves this problem. (Maybe related to some nvme devices)
Maybe you can search for it in the mailing list ;)
-----Original Message----- From: Nico Schottelius <nico.schottelius@ungleich.ch> Sent: 19 March 2021 20:12 To: ceph-users <ceph-users@ceph.io> Subject: [ceph-users] LVM vs. direct disk acess
Good evening,
I've seen the shift in ceph to focus more on LVM than on plain (direct) access to disks. I was wondering what the motivation is for that.
From my point of view OSD disk layouts never change (they are re-added if they do), so the dynamic approach of LVM is probably not the motivation.
LVM also adds another layer of indirection and it seems it would be of disadvantage performance wise as well as added complexity for management. The former is probably only a minor degradation, the latter is something I see more as obstacle for maintenance.
At ungleich we are using a custom script [0] to format a disk with two partitions, one for the metadata, one for the rest, which seems to be more simple.
I assume there are good reasons not to do as we do, but I was wondering what the practical reasons actually are.
Best regards,
Nico
[0] https://code.ungleich.ch/ungleich-public/ungleich-tools/- /blob/master/ceph/ceph-osd-create-start
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