[Users] Remote storage and migration

[Dietmar Maurer]

> Hello, list. I've been using OpenVZ since last year. Now I'd like to
> configure the cluster I've been using to use remote storage, so that
> migrations do not require to copy the container's filesystem.
> 
> Reading the wiki and the forum, I've learned that NFS is not
> recommended, but I don't know why. iSCSI has been suggested as a way
> to go, although no success story supported the suggestion. Finally,
> somebody said that he was using GFS without problems, but one of the
> OpenVZ developers said (at that time) that GFS was not recommended due
> to stability issuess.
> 
> I've been told that remote storage with OpenVZ is not a well-known
> area, but I have to ask anyway, so as to leverage in previous
> experiences. Any information is welcome, even more the problems that
> were found with each approach, so that I know were to go and were not
> to.

I am also interested to make openvz more flexible. The new proxmox release
will have a very flexible storage model which supports iscsi/nfs/lvm, but
it is currently KVM only, because openvz lacks that feature.

I am especially interested in mounting devices (lvm) as container root,
something like

# mount -t ext3 /dev/xzy /var/lib/vz/private/777

Looking at the source (vzctl/src/fs_simfs.c vz_mount) it seem to be
easy to implement. If ROOT is a device we use 'ext3' instead of 'simfs'.

But I have no idea how this interacts with the rest of the openvz code?
Does quotas work that way? Or would it be better to use an additional 
configuration option to specify the root device:

ROOTDEV=/dev/xzy
ROOT=...
PRIVATE=...

We then simply mount ROOTDEV first, then use simfs as usual?

I can write that code if some of the OpenVZ developers give me some hints.

- Dietmar