On Tue, 2005-10-04 at 12:24 -0500, Justin Conover wrote:
tune2fs
-m reserved-blocks-percentage
-r reserved-blocks-count
If what I have read is correct, -m by default uses 5% of the disk
space for "reserved root use" On my server at home with a /home of
1TB thats about 50GB of wasted space.
Is this reserved space actually used by ANYTHING? Like LVM, some kind
of fragmentation?
well for emergency root stuff; logging in without any disk space is
hard; lots of stuff wants to make temporary files etc.
but your second point it true too: most filesystems (ext3 but most
others) start to fragment like hell if they go over about 95% full.
Think of it this way: if you have half your disk empty, the filesystem
can do a proper job of finding non-fragmented space.
If only 0.0001% is free, it has almost no freedom of choice, resulting
in "you get it in whatever order some things become free".
Those are sort of extremes; there's been a bunch of research and the
outcome was that 5% free seems to be sort of the turning point in this
respect.
I suspect that research predates the Tb sized volumes, so I don't know
if it maybe is 1% on such volumes, but then again to some extend the
freedom needed will scale with the FS size