Filesystem question

David Collier-Brown David.Collier-Brown at
Thu Oct 12 19:57:35 GMT 2000

Michael Tokarev wrote:
> BTW, but is the OS filesystem cache was introduced for this!?
> I see that all unices around me (linux, solaris, sco) have very
> intelligent fs cache, that can work far better than samba implementation.
> For our site, I see disk access only when the first client accesses
> the directory, subcequent accesses takes results from fs cache
> (for all other clients also) -- there is no disk activity there.
> If samba will have its own cache implementation, then on this system
> this actually will _decrease_ performance, will require more additional
> resources (notably RAM) and decrease stability.  I recall that kernel
> know far more information about filesystem than samba can have, and
> kernel knows also available RAM size that can be used for caches,
> and it keeps cache only once while samba will keep it in each smbd
> process...

	That particular cache doesn't have behavioral
	knowledge about the usage pattern, and has to
	be pretty general.  This causes me annoyance,
	as I expect far faster directory searches than
	I get, even when the directory blocks are all
	in core and most of the inodes are cached as well.

	OS vendors do work on this (I'm happy to say
	I benchmarked a Solaris 8 improvement in this
	very area this spring), but some things are
	appropriate to cache in applications which know
	the usage pattern of their users.

	As an example, we **don't** cache the stuff you
	send to a client when they ask for a directory 
	traversal, and so have to pull it back from the OS
	even though we know the application is going to
	(stupidly) ask for it again!

	Some careful groveling over the requests sent
	by Windows Explorer may well point to places where
	both we and Microsoft can improve things.

David Collier-Brown,  | Always do right. This will gratify some people
185 Ellerslie Ave.,   | and astonish the rest.        -- Mark Twain
Willowdale, Ontario   | //
Work: (905) 415-2849 Home: (416) 223-8968 Email: davecb at

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