File system performance

[Richard Todd]

dawes at suphys.physics.su.OZ.AU (David Dawes) writes:
>I too am using ESIX rev D with ffs.  One of my file systems became heavily
>fragmented, and got to the point where there were 0 free blocks, and
>5000 free frags.  df reported 10000 blocks free, but attempting to write
>to the file system resulted in "Disk full" errors.  This meant that I
>had an unusable 5MB on a 65MB file system. (BTW, there were plenty of free
>inodes.)

>Is this how FFS is supposed to work, or is there a problem with the ESIX
>implementation?

  Well, that's how FFS works on other machines (I've hit it on Apple Unix
2.0, which includes Berkeley FFS).  Hitting the no-free-blocks limit when
you've got 5M free in fragments is a little unusual; I was hitting the
limit with only ~250K of fragments free on a 282MB filesystem, and on the
(frequent) occasions when the local campus BSD machine fills a partition it
gets down to fairly small values of free-fragment-space (again, in the 
neighborhood of a couple hundred K on ~200MB filesystems).  Evidently you
managed to stumble on a pathological worst-case....
--
Richard Todd	rmtodd at uokmax.ecn.uoknor.edu  rmtodd at chinet.chi.il.us
	rmtodd at servalan.uucp
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