[Linux-cluster] GFS2 and fragmentation

Scooter Morris scooter at cgl.ucsf.edu
Tue Aug 7 22:06:24 UTC 2012

Hi All,
     We have a RedHat 6.2 cluster with 4 nodes using GFS2 for shared 
filesystems.  One of the filesystems we need to share is 
/var/spool/mail.  In general, with recent upgrades and improvements to 
GFS2, which has been working really, really well.  We're starting to see 
some significant fragmentation on files in the filesystem, though, even 
after recreating the filesystem after the RHEL 6 upgrade.  My 
understanding was that there were fixes in RHEL 6 that made 
defragmentation un-(or less?) necessary, but we're seeing a disturbing 
increase in the amount of fragmentation since the upgrade.  By the way, 
we're seeing numbers in the range of 4,000-6,000 extents/GB for some of 
these files, which seems a bit large.
     So, I've got two questions:

     1. At what point should we be worried about the number of extents?
     2. Are there plans for a defragmentation tool?


-- scooter

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