[OpenAFS] Volume rename with active volumes

[Jeffrey Altman]

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File handles on the location operation system are associated with the
AFS File ID (volumeId, vnodeId, uniquifier) and not the volume name.  A
volume rename is a modification the volume location database that does
not alter the volumeId nor its location.  Therefore, client systems that
are actively using the volume will not be immediately affected by the
rename.

The rename will be noticed when one of two things happens:

 1. The old mount point contents are evaluated and the volume name
    does not exist.

 2. The new mount point contents are evaluated and the volume name
    does not exist.

The clients treat the volume location information as being valid for two
hours.  One possible course of action would be to alter the mount point
so that the target refers not to the old volume name but to the
volumeId.  Then wait two hours and perform the volume rename followed by
updating the mount point to refer to the new volume name.

Jeffrey Altman

On 9/2/2011 5:04 PM, Richard Brittain wrote:
> Hi,
>   we need to rename some data volumes, but they tend to be busy most of=

> the time, so I did some experiments with 'vos rename' and 'fs mkmount' =
etc.
>=20
> As expected, most clients get an error if the vos rename has happened,
> but not the rmmount/mkmount/release (since the mount points are
> replicated).
> However, a client with an open file on the volume seemed to be fine and=

> continued to work after rename, and even reported the correct voluume
> name to 'fs lq'.
>=20
> I tried two tests:
>  - hold a file open for writing and append lines.  Most or all of the
> activity would be to the local cache.
>  - repeatedly open/append/close a file.  I assume this pushed it out to=

> the fileserver.  This also worked without error.
>=20
> Given this, is it safe to rename active volumes ?.  I can't figure out
> how the active clients get this right.
>=20
> Thanks,
>=20
>  Richard


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