Date: Wed, 9 Jun 2004 22:10:45 +0200 From: Stijn Hoop <stijn@win.tue.nl> To: Bill Moran <wmoran@potentialtech.com> Cc: freebsd-questions@freebsd.org Subject: Re: Improper shutdown of system / Fragmentation Problems / Boot Message-ID: <20040609201045.GE11712@pcwin002.win.tue.nl> In-Reply-To: <20040609155900.3fb65c2a.wmoran@potentialtech.com> References: <200406091845.i59Ij8Y12090@clunix.cl.msu.edu> <200469142140.786530@IBM-R40> <20040609194439.GD11712@pcwin002.win.tue.nl> <20040609155900.3fb65c2a.wmoran@potentialtech.com>
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--/e2eDi0V/xtL+Mc8 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jun 09, 2004 at 03:59:00PM -0400, Bill Moran wrote: > Stijn Hoop <stijn@win.tue.nl> wrote: > > On Wed, Jun 09, 2004 at 02:21:40PM -0500, Scott wrote: > > > As a newbie to FreeBSD, I may be way off base, but it seems=20 > > > very logical to me that the size of your drive or partition=20 > > > would make a difference on at what percentage full one would=20 > > > start to notice problems. > > >=20 > > > In terms of megs/gigs 80% of 120 gigs still has a lot of=20 > > > work space left. 80% of 4 gigs is not much. I would think=20 > > > with a larger drive/partition, one could run at a higher=20 > > > percentage before trouble started. > > >=20 > > > It makes sense to me anyway :) > >=20 > > That's what one would like, but UFS doesn't work that way. It's > > allocation algorithm assumes 10% of the disk is free -- regardless > > of actual size. Or so I've been told (multiple times). > >=20 > > IMHO this is a bit ridiculous -- I mean, given 1 TB of space (nearly > > feasible for a home server right now), why would an FS allocator need > > 10% of that if the files on the volume are averaging 10 MB? > >=20 > > But then again, and this is worth noting -- I'm certainly nowhere near = as > > clueful as others on how to design a stable & fast file system. Seeing= as > > UFS1 is still in use, and has been for the last 20 years (think about > > it!), I think maybe the tradeoff might make sense to an expert... > >=20 > > BTW, note that you really need to consider the perfomance drop for your= self > > -- like others said, if the files on the volume change infrequently, > > performance matters little, and space more so. >=20 > I think you've missed the point. I most certainly do that a lot of the time :) > The designers of UFS/FFS did not design the filesystem to require 10% free > space in order to perform well. OK, I did not know that. > They developed the best, fastest (thus the name "fast file system") files= ystem > algorithms they could come up with. That I knew, and still experience every day :) > Then, during testing, they found that these algorithms started to perform > really poorly when the filesystem got really full. Thinking this might be > important, they tested further until they knew exactly what point the > performance started to drop off at. They then went one step further and > developed another algorithm in an attempt to maintain as much performance > as possible even when the filesystem got very full. This is why you'll > occasionally see the "switching from time to space" message when your > filesystem starts to fill up. The filesystem drivers are doing their best > to degrade gracefully. I understand. > Now, I'm not going to say that there is no more that can be done. I thin= k the > fact is that the two algorithms work well enough that nobody has bothered= to > invest the research into improving them. (That combined with the fact th= at > disk space keeps getting cheaper and cheaper, makes it unlikely that anyo= ne > will invest much $$$ into researching how to use that last 10% while still > maintaining top performance). Well, although disk is cheap, seen absolutely it's still a lot of space tha= t's "wasted". I do understand the issues, and your posts, this and the previous reply, have made things clearer -- thanks.=20 --Stijn --=20 "I'm not under the alkafluence of inkahol that some thinkle peep I am. It's just the drunker I sit here the longer I get." --/e2eDi0V/xtL+Mc8 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAx27FY3r/tLQmfWcRAiKTAJ9HwAA768plNqWEzXJov2ckDEVOOwCbBPOe qja04TRUD5Itcr/6w/N06bA= =D9GC -----END PGP SIGNATURE----- --/e2eDi0V/xtL+Mc8--
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