[PVE-User] Why are images and rootdir not supported on CephFS?

Frank Thommen f.thommen at dkfz-heidelberg.de
Sun Feb 16 17:26:01 CET 2020

Thank you for the link.

Even though Fabian Gruenbichler writes in the bugreport 
(https://bugzilla.proxmox.com/show_bug.cgi?id=2490#c2) that Ceph RBD 
offers all features of CephFS, this doesn't seem to be true(?), as 
CephFS supports "vztmpl iso backup snippets" and Ceph RBD "images 
rootdir" (https://pve.proxmox.com/pve-docs/chapter-pvesm.html), so these 
two storage types are complementary and RBD cannot replace CephFS.

What would be a good practice (CephFS and RBD are already set up): 
Create an RBD storage on the same (PVE based) Ceph storage that already 
has CephFS on top of it and use one for templates and backups and the 
other for images and rootdir?

Won't it create problems when using the same Ceph pool with CephFS /and/ 
RBD (this is probably rather a Ceph question, though)

Additionally this might create problems with our inhouse tape backup, as 
I don't think it supports backing up object storage...


On 15/02/2020 00:38, Gianni Milo wrote:
> This has been discussed in the past, see the post below for some answers...
> https://www.mail-archive.com/pve-user@pve.proxmox.com/msg10160.html
> On Fri, 14 Feb 2020 at 22:57, Frank Thommen <f.thommen at dkfz-heidelberg.de>
> wrote:
>> Dear all,
>> the PVE documentation on
>> https://pve.proxmox.com/pve-docs/chapter-pvesm.html#_storage_types says,
>> that "[File level based storage technologies] allow you to store content
>> of any type".  However I found now - after having combined all available
>> disks in a big CephFS setup - that this is not true for CephFS, which
>> does not support images and rootdir.
>> What is the reason, that of all filesystens, CephFS doesn't support the
>> main PVE content type? :-)
>> Ceph RPD on the other hand, doesn't support backup.
>> This seems to rule our Ceph (in whatever variant) as an unifying, shared
>> storage for PVE.  Or do I miss an important point here?
>> Frank
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