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Re: filesystem fragmentation stats?



On Sat, 9 Jul 2005, evilninja wrote:
Damian Menscher schrieb:
That said, is there a way to check the overall level of fragmentation of
a live ext3 filesystem?  I know about filefrag, but that's for specific
files.  And I think e2fsck tells you, but only if you take the
filesystem offline for the scan.

"tune2fs -l" tells you about "Fragments per group", and "fsck.ext2 -nv" opens the fs read-only and print some nice stats after that.

I noticed the "Fragments per group", but haven't been able to find anything that documents what it means. Could someone here comment?


Running e2fsck -nvf gave the info I was looking for:

On my mail partition:
      93 inodes used (0%)
      30 non-contiguous inodes (32.3%)
         # of inodes with ind/dind/tind blocks: 44/17/0
   60540 blocks used (45%)
       0 bad blocks
       0 large files

      80 regular files
       4 directories
--------
      84 files

On my home partition:
  191326 inodes used (7%)
   11084 non-contiguous inodes (5.8%)
         # of inodes with ind/dind/tind blocks: 21649/707/0
 4581594 blocks used (86%)
       0 bad blocks
       0 large files

  174096 regular files
   15787 directories
       5 fifos
     274 links
    1421 symbolic links (1356 fast symbolic links)
       8 sockets
--------
  191591 files


So, interestingly, the home directories haven't gotten too fragmented despite being at >90% usage for several months (much of that time at
95%). Apparently the 5% reserved for the system factors in here.
That's certainly a relief!

On the other hand, the mail spools are getting horribly fragmented (>30%), probably because mail programs are deleting messages out of the middle of the spools? It's hard to imagine any other reason for 30% fragmentation on a filesystem that's less than half full. (Another system I manage also shows high fragmentation for the mail spool, so I think this must be a generic problem.)

Damian Menscher
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