Re: [patch] pagecache-2.3.9-H3, bmap & ext2fs cleanup patch

Matti Aarnio (matti.aarnio@sonera.fi)
Sun, 27 Jun 1999 21:01:00 +0300


On Sun, Jun 27, 1999 at 10:08:11AM -0700, Linus Torvalds wrote:
> The best argument for having the filesystem know about devices is to have
> filesystems that can "migrate" files from one device to another. It can be
> done other ways too, but basically it is really nice for "intelligent"
> filesystems that do (for example) dynamic load balancing or that have
> multiple levels of caching.

Eee... Big blue MVS rearing its head ?
Actually there are other uses for such things too, and likely
more common ones.

> Basically I'm talking about hierarchical filesystems: everything looks
> like one large filesystem, but the filesystem itself can dynamically move
> things from a slow medium to a fast medium according to usage patterns.
> Old stuff that is seldom used is on a slow disk (or disk arrays), while
> stuff that is used regularly is on a fast one.

Yes, and ultimate storage medium is magnetic tape (for files).
A careless egrep thru the filesystem causes massive randomish
tape activity (at the robot), of course..

Still, one can do a 'find' thru the entire filesystem, and stat()
will yield sensible info. ( + possible magic flag telling the
file is actually offline ...)

> I'm not writing one, and I don't know of anybody _else_ writing one
....
> Linus

Me neither -- not now, anyway, but e.g. SGI XFS (as I understand
it) can use that facility too.

/Matti Aarnio

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