From: Mark McLoughlin [mailto:markmc@redhat.com]
...
> [IH] this may change (more than one type of storage)
More than one type or no type restriction at all? i.e. we have:
<datacenter type="nfs"
...
Do you suggest we move to:
<datacenter
<storage_type>nfs</storage_type
<storage_type>iscsi</storage_type
or are you saying that in future the storage type attribute will go
away?
[IH] will stay. May allow mixed FC/iScsi.
...
...
> > 4) Require a data center to be specified at creation time
and
> > use that to choose a host from one of the clusters in the data
> > center. We could remember that data center and allow no data
> > center to be specified when invoking 'attach' later.
> [IH] this requires that setting the storage domain all hosts will
already
> have access to it in the cluster. Sounds a bit limiting.
Okay, where am I going wrong with this logic:
- At creation time, all we need is any host with access to the
storage
- I can't see an obvious use case where one would create a storage
domain and not immediately attach it to a datacenter
[IH] creating an export
domain, to allow V2V to it. it has to be detached
(or inactive, not sure) from all data centers to be used by V2V. there is
also a powershell verb which allows to init a data center by passing a group
of storage domains today (look at init-datacenter which accepts a list of
storage domains). I'm not sure what was the use case which merited this one.
- Before attaching a storage domain to a datacenter, all hosts in the
datacenter should have access to the storage
- Therefore it makes sense to specify a datacenter (rather than a
host) when creating a storage domain
> One could also later attach it to another storage domain.
> Btw - a storage domain can be attached to multiple data centers,
And all hosts within the multiple datacenters should have access to the
storage, right?
> and may have a different status in each of them.
Huh? That would suggest a storage domain's status needs to be modelled
like:
<datacenter
....
<storage_domain_statuses
<storage_domain_status
<storage_domain href="..."/
<status>....</status
</storage_domain_status
</storage_domain_statuses
How is this expressed with the powershell API - do you get a different
storage domain object from get-storagedomain depending on which
datacenter ID you supply?
[IH] yes. A storage domain may have an error in one data
center (hosts not
able to access it, moved to maintenance, lockes, etc., but be viable in
another).
Also, which of the two statuses do you mean:
StorageDomainStatus { Unknown, Uninitialized, Unattached, Active,
InActive, Locked }
[IH] this is per domain, and is shown per data center.
StorageDomainSharedStatus { Unattached, Active, InActive, Mixed,
Locked
[IH] this is an aggregation of the per data center statuses, to show a
single status for the data center, without drilling down to different data
centers it is attached to.
}
What is the difference between the two?
[IH] first is shown on the storage domain
tab, data center subtab (or data
center tab, storage domain subtab). Second is shown in the main storage
domain tab.
> > 5) Same as (4), except we automatically attach the storage domain
to
> > the cluster as part of the creation. We would still have
'detach'
> > and 'attach' actions, though.
> [IH] this makes creation of a storage domain an action that has to be
> synchronized on all hosts in a data center.
Could you explain that a bit further?
[IH] I think that before adding a storage
domain to a data center, there is
a check all hosts can see it correctly (not sure. there is a difference
between first add, and later operations).
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