[OpenAFS] Changing reserved block on ext3 with fs running

Stephan Wonczak a0033@rrz.uni-koeln.de
Wed, 5 Oct 2005 13:20:32 +0200 (MET DST)

  Hi list!
  Quick googling turned up nothing useful, so here goes.
  While installing a couple of new fileservers on Linux, we created
several huge vice-partitions, using ext3 on these. Since we were in a bit
of a hurry, we did not tune the mkfs-parameters, so we are left with the
defaults. We can't do much about the number of inodes, but we are still
sitting with the 5% reserved blocks. Over all partitions this adds to a
lot of wasted space (~500GB).
  Now, obviously we would rather use this space :-)
  We have a throwaway cell similar to our production environment where I
was able to do a bit of testing. (OpenAFS 1.2.13 if that matters) First I
looked at the number of reserved blocks on the vicep-filesystem (ext3):

  tune2fs -l /dev/somedevice

  which gave me some 26000 reserved blocks.

  Then I changed the number of reserved block with

  tune2fs -r 1000 /dev/somedevice

  'df -k' showed the increased usable space, as did 'vos parti'. I then
set the number of reserved blocks to some 36000, and again the change was
reflected correctly in both 'df' and 'vos parti'. To be on the safe side,
I changed everything back to the original values.

  Now the question: Are there any repercussions when changing the number
of reserved blocks in this way, or are there any subtle side effects on
the fileserver?

	Dipl. Chem. Dr. Stephan Wonczak

        Zentrum fuer Angewandte Informatik (ZAIK)
        Regionales Rechenzentrum der Universitaet zu Koeln (RRZK)
        Universitaet zu Koeln, Robert-Koch-Strasse 10, 50931 Koeln
        Tel: ++49/(0)221/478-5577, Fax: ++49/(0)221/478-5590