[OpenAFS] recovering corrupted save on file

[Jeffrey Altman]

This is a cryptographically signed message in MIME format.

--------------ms070700080400030000080307
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit

The cache does not store files it contains blocks.  There is no
guarantee that a file will be entirely contained in the cache.

You do not specify which OS you are using.  On Windows the cache
file is simply a paging file for dedicated virtual memory.  Assuming
the afsd_service.exe is shut down cleanly it would be possible to
write code that could walk the contents of the cache to piece together
the blocks of the file that exist.  However, no such tools currently
exist.  The tool would have to be able to determine the cell, volume,
vnode, and unique values for the file in order to find the correct
stat cache entry and data buffers.

Jeffrey Altman


David Bear wrote:
> We have one room in one building that on occasion has some very
> strange network disruption. It last about 8 minutes. When it clears
> everything works fine.
> 
> The problem is that if someone has a file stored in an afs server open
> on their client, AND they perform a save when the network has its
> tantrum, the file is corrupted; either truncated to 0 bytes or filled
> with garbage.
> 
> Is there any possible way to recover a file like this from the local
> cache manager? I assume the local machine would commit some form of
> the file to the local disk -- stored by the cache manager and then
> actual write to the network would happen later. 
> 
> Of course we are trying to troubleshoot the network -- but at this
> university that's not something that happens very fast... especially
> when the problem is only intermittent.

--------------ms070700080400030000080307
Content-Type: application/x-pkcs7-signature; name="smime.p7s"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="smime.p7s"
Content-Description: S/MIME Cryptographic Signature
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--------------ms070700080400030000080307--