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Re: Local repository access / AFS?

From: Greg Hudson <ghudson_at_MIT.EDU>
Date: 2002-09-25 16:34:59 CEST

On Wed, 2002-09-25 at 03:11, Markus Mårtensson wrote:
> Would it be safe to assume that multiple users could access a
> repository database at the same time on a distributed filesystem?

That depends on what kind of locking Berkeley DB uses. AFS supports
advisory locks, but not range locks. Unfortunately, it looks like
Berkeley DB might use range locks based on a quick inspection of the
code; I can't be sure.

There is also an efficiency question; AFS isn't really designed for
one-huge-file-with-many-accessors. Its 64K chunking would probably make
a single accessor be reasonably efficient, but it may be that making one
change anywhere in the file will invalidate the cache of anyone
accessing any part of the file, which is no good.

Ignore Branko's comments about umasks; AFS doesn't care about Unix mode
bits, but you're probably familiar with that.

> If it is not currently possible to do, what parts of the code would
> require changes?

After 1.0 comes out (some sunny day), I hope to start work on a
filesystem back end with a direct mapping to the underlying filesystem.
It would be much more AFS-friendly.

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Received on Wed Sep 25 16:38:39 2002

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