[OpenAFS] Re: bonnie++ on OpenAFS

Matt W. Benjamin matt@linuxbox.com
Tue, 23 Nov 2010 10:14:44 -0500 (EST)


Is "write-on-close" was an expectation which could be broken?  It is the case that AFS has strongly expressed that its semantics are (in general) _sync-on-close_, and it's meaning is that an application which has closed an AFS file may consider any writes it made to be stable, and visible to other clients.  Write stability is not assured only on close, an application may explicitly sync when convenient.  I'm not sure, first, how a client can ever have been assured that its writes were not stabilised before it closed its corresponding file(s), nor, how it would benefit from this?  For example, the client may not revoke its own operations on the file prior to closing it.  Which is to say, I think the CM is free to stabilise ordinary writes when any convenient opportunity arises.  Feel free to flame now...


> The problem is that we don't make good decisions when we decide to  
> flush the cache. However, any change to flush items which are less  
> active will be a behaviour change - in particular, on a multi-user  
> system it would mean that one user could break write-on-close for  
> other users simply by filling the cache.
> Cheers,
> Simon.
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Matt Benjamin

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