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