[OpenAFS-devel] RFC: Status returned by vos for pre-attached volumes on demand-attach

[Jeffrey Altman]

Alistair Ferguson wrote:
> There are at least four options:
> 1. expose all underlying states to vos examine
> 2. expose pre-attached to vos examine
> 3. convert pre-attached to on-line for vos (the current behavior)
> 4. convert pre-attached to off-line for vos
> 
> Option 3 is currently implemented and is the least desirable.
> 
> Our suggestion is that we implement option 1, which will require
> exposing the current volume state onto the inUse field in the
> FillVolInfo function in the volserver.  The vos command would need to be
> modified to be aware of the new values, but unmodified vos commands
> would report off-line for volumes in a
> state other than fully attached.
> 
> Note that options 1 and 2 involve a change in behaviour for sites running
> demand-attach.

The Windows client performs extensive volume status monitoring in order
to export that status info to third party kernel drivers that can use
that state info to fail over between cell clones or redirect offline
paths to alternate locations.   As part of this logic,
RXAFS_GetVolumeStatus is executed on inaccessible volumes to obtain
their current status.   From the perspective of the clients that are
currently shipping, option 3 is the most desirable and option 4 will
break them.

I appreciate the desire to export additional information.  I believe
that this should be done by a new RPC, RXAFS_GetVolumeStatus2, that
documents the new states and their meanings.  Clients that use the new
RPC will be expected to be knowledgeable of the new states.

A proposal to implement this new RPC should be made to the
afs3-standardization mailing list.

Jeffrey Altman