[Linux-cachefs] multiple clients and FS coherency

David Howells dhowells at redhat.com
Wed Nov 10 12:18:51 UTC 2004


> I was wondering if linux cachefs can make my life easier - 2 specific
> questions:
> 1.  When I re-sync image back from my laptop (after a disconnect),
> would it be faster (would linux cachefs Write-back only changed
> blocks/pages instead of the whole file)?

That's a question for the netfs designers. CacheFS doesn't care. There are
plans afoot to permit the netfs to log uncommitted changes in the cache, but
it's up to the netfs to dictate how they're used.

> 2.  If multiple clients are working on the emulated disk file, does
> cachefs pretty much rely on the underlying netfs to provide the
> coherency/locking?

CacheFS is hidden from the user by the netfs. As far as the user is concerned,
CacheFS does not exist, except to affect performance of the netfs. Think of it
like this:

	+---------+       +---------+       +---------+
	|         |       |         |       |         |
	|         |       |         |       |         |
	| Network |<----->|  NetFS  |<----->|  User   |
	|         |       |         |       |         |
	|         |       |         |       |         |
	+---------+       +---------+       +---------+
                               |
                               |
			  +---------+
			  |         |
			  |         |
			  | CacheFS |
			  |         |
			  |         |
			  +---------+

David




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