[libvirt] ESX and inaccessible storage pools

Dave Allan dallan at redhat.com
Mon Apr 19 13:41:27 UTC 2010

On Sun, Apr 18, 2010 at 10:55:04PM +0200, Matthias Bolte wrote:
> I'm currently implementing the storage driver for ESX and have a
> mapping problem.
> libvirt storage pools can be either running or inactive just like the
> domain. ESX is a bit different here. A datastore is always active. It
> can be inaccessible, e.g. if an NFS is mounted as datastore but the
> NFS server went unreachable. I discussed this with Daniel on IRC and
> he summarized it like this:
>   <DV> they are defined, the system knows them, but they are not
> available for use
> The question is, what should the ESX driver do with inaccessible datastores?
> Option 1: They could just be represented as inactive storage pools,
> but libvirt's semantic for inactive storage pools includes that the
> user can start an inactive storage pool. That's not possible for an
> inaccessible datastore, so the driver would report an error if a user
> tries to start an inaccessible storage pool.

I don't think this is all that bad an option.  The argument against it
is (I think from what you're saying) that we know in advance that the
pool isn't going to start, so allowing the user to attempt to start it
is pointless.

> Option 2: Just ignore inaccessible datastores and make the ESX storage
> driver to pretend that they don't exist. But this would hide
> information from the user.
> Option 3: Extend libvirt's API for inaccessible storage pools.

This seems like the best option to me since libvirt could then use the
pool status to give some indication to the user that pool start
attempts are going to fail.


> There are possibly other options and I'd like to hear your comments
> and suggestions.
> Matthias
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