BTW: I am reducing it to 2% since.. long long time. I haven't seen an issue arising from this at all.
regards Peter On Mon, Aug 24, 2015 at 10:17 AM, Trent W. Buck <[email protected]> wrote: > David Zuccaro <[email protected]> > writes: > > > On 21/08/15 12:24, Trent W. Buck wrote: > >> > >> By default mke2fs reserved 5% of the filesystem for uid 0. > >> This is also used as a staging area to reduce fragmentation. > >> > >> df does not include this area in the "free" size, > >> so if you fill a disk *as root*, > >> you must remove >5% for df to show any change. > >> > >> 30G is about 2% of 1.4T, so that's not enough. > >> > >> You can remove this reserved area using tune2fs, > >> but that is a bad idea. > >> > >> > >> > > Thanks Trent, that would explain the anomaly. I did not know that that > > the 5% reserved area was accessible to root (I was running the back up > > as root). Would it be ok to reduce the reserved area to say 1%? > > It won't hurt. > > Without reserved space, you will get more fragmentation (if you > repeatedly fill the filesystem). > > BUT you're running the backup as root, > so it effectively ignores that reserved space ANYWAY. > > e2fsck -f reports fragmentation as a percentage, > but I'm not sure how believable that number is. > > * * * > > You could just put up with it. > IME fragmentation isn't a big deal on ext. > > You could change the reserved user ID from 0 (using tune2fs), > so the root-owned rsync can't use the reserved space. > > You could run a defrag program occasionally. > This mostly consists of writing a new copy of each file, > along these lines (untested, pre-coffee): > > nice ionice -c3 find -O3 /srv/backup -xdev -type f -links 1 -size +1M \ > -exec cp -v {} {}~ \; \ > -exec mv -v {}~ {} \; > > ...but it is easy to break unusual files (e.g. hard-linked, sparse) > without realizing until it's too late. > > Last time I looked, all of the ext defrag programs were written by > recent Windows refugees and I didn't trust them to get edge cases right > any better than the above. > > _______________________________________________ > luv-main mailing list > [email protected] > http://lists.luv.asn.au/listinfo/luv-main >
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