[OpenAFS-devel] Silly problem: support for partitions vicepa-z, vicepaa-zz

[Jeffrey Hutzelman]

--On Monday, September 15, 2008 04:34:57 PM +0200 Rainer Toebbicke 
<rtb@pclella.cern.ch> wrote:

> We now ran into a silly little naming problem with our vicepX partitions
> - named a bit too generously in order to match RAIDs connected to a FC
> switch.
>
> I am now faced with having a /vicepja-/vicepjd, ..., /vicepka-/vicepkd
> etc... and of course although the file server attaches them bravely, the
> vos utilities and the vldb resist.
>
> The proposed changes are straightforward: continue limiting to 255 the
> total number of partitions on a file server so that the RPCs and array
> declarations don't blow up, but allow partition ids from 0 to 27*26-1.
>
> This goes together with a change in the vlserver where the limitation to
> 255 partitions does not seem to serve a constructive purpose anyway.
>
> Changing the code rather than a silly layout convention sounds drastic,
> but on the other hand running into a difficult-to-remember barrier in
> midst the /vicepiX series is ugly as well, so I consider this more a
> clean-up operation.
>
> Anything that I might have overlooked?

Partition ID's are used to record the location of a volume in the VLDB, and 
the on-disk database format only has room for 8 bits of partition ID.  So 
making a change such as you propose would require a change to the on-disk 
VLDB format.  It may be possible to make such a change in a 
backward-compatible way, but it wouldn't be easy.  I'd suggest instead 
abandoning the idea that vice parititon names have any structure or 
meaning, rather than just being a way of writing an 8-bit number.

-- Jeffrey T. Hutzelman (N3NHS) <jhutz+@cmu.edu>
   Carnegie Mellon University - Pittsburgh, PA