From mboxrd@z Thu Jan  1 00:00:00 1970
To: 9fans@cse.psu.edu
From: Wladimir Mutel <mwg@alkar.net>
Message-ID: <8ur18f$11jj$2@pandora.alkar.net>
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References: <20001113201911.6003E199EB@mail.cse.psu.edu>
Subject: Re: [9fans] AFS-client for Plan9 - ?
Date: Tue, 14 Nov 2000 09:58:14 +0000
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anothy@cosym.net wrote:
> //Local caching would be great, I think.

> okay, let me say off the bat i have no idea how
> AFS handles caching, so this comparison may be
> totally inapropriate. but for fs caching in
> Plan 9 (without 9pAFS), take a look at cfs(4)
> and the -C option to mount in bind(1).

> if your goal is talking to AIX or other Unix
> boxes, take a look at u9fs(4).

	Here is a quote from their doc
http://oss.software.ibm.com/developerworks/opensource/afs/docs/html/AdminGd/auagd007.htm :

AFS Implements Save on Close

When an application issues the UNIX close system call on a file, the Cache
Manager performs a synchronous write of the data to
the File Server that maintains the central copy of the file. It does not
return control to the application until the File
Server has acknowledged receipt of the data. For the fsync system call,
control does not return to the application until the
File Server indicates that it has written the data to non-volatile storage
on the file server machine. 

When an application issues the UNIX write system call, the Cache Manager
writes modifications to the local AFS client cache
only. If the local machine crashes or an application program exits without
issuing the close system call, it is possible that
the modifications are not recorded in the central copy of the file
maintained by the File Server. The Cache Manager does
sometimes write this type of modified data from the cache to the File
Server without receiving the close or fsync system call,
for example if it needs to free cache chunks for new data. However, it is
not generally possible to predict when the Cache
Manager transfers modified data to the File Server in this way. 

The implication is that if an application's Save option invokes the write
system call rather than close or fsync, the changes
are not necessarily stored permanently on the File Server machine. Most
application programs issue the close system call for
save operations, as well as when they finish handling a file and when they
exit. 


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