Path: utzoo!mnetor!uunet!husc6!uwvax!umn-d-ub!rutgers!bellcore!faline!thumper!ulysses!terminus!rolls!mtuxo!homxb!genesis!hotlr!dkc
From: dkc@hotlr.ATT (Dave Cornutt)
Newsgroups: comp.unix.wizards
Subject: Re: Compressing unix disks
Message-ID: <208@hotlr.ATT>
Date: 14 Mar 88 18:26:07 GMT
References: <1071@ndmath.UUCP> <305@marconi.SW.MCC.COM> <1097@hubcap.UUCP> <4336@pwcs.StPaul.GOV>
Reply-To: dkc@hotlr.UUCP (Dave Cornutt)
Organization: Not much, but I'm working on it
Lines: 17
Summary: 90% of the total, not 90% of the 90%

You're right.  In average use, the threshold where the BSD FFS starts to
have trouble finding free blocks is at 90% of the TOTAL file space
available, NOT 90% of the 90%.  Incidentally, the reserve is there to
avoid performance problems that occur when the disk gets near full;
it wasn't really intended to be a "system manager reserve", in the
same sense that the last slot in the process table is.

Actually, on file systems consisting mostly of large files, I've been
able to push the reserve down as low as 3% without noticable performance
problems.  (You can adjust this using "tunefs".  Make sure the file
system is unmounted first.)  On something big like an Eagle, this could
mean an extra 30Mb to play with.
-- 
Dave Cornutt, AT&T Bell Labs (rm 4A406), Holmdel, NJ (Note new address!)
UUCP:{ihnp4,allegra,cbosgd}!hotly!dkc (path stolen from Shelley)
"The opinions expressed herein are not necessarily my employer's, not
necessarily mine, and probably not necessary"