Hammer fileystem disk full problem

Matthew Dillon dillon at apollo.backplane.com
Sat Jun 15 11:50:07 PDT 2013

:>     hammer reblock <fs> 90
:>     Each PFS needs to be independently reblocked.
:>                                         -Matt
:Thanks, Matt!  After doing just the 10% on each PFS, I had recovered enough
:space to get back in operation.  I read the man page, but I'm still not
:clear on what exactly the fill percentage does?

    Basically HAMMER1 doesn't keep track of free space on a block-by-block
    basis.  It keeps track of free space on a segment (~2MB) by segment
    basis and iterates through the segment until it fills up.  In order
    to free space, the segment has to become 100% empty.

    By default the reblocker will reblock out of all storage segments,
    which can temporarily require more storage during the run until it
    sorts things out.  This is desireable for normal operation because
    it defragments the disk quite well.  But it doesn't work well if the
    filesystem is completely full.

    Telling the reblocker to only reblock out of storage segments that
    are underutilized has a better chance of clearing those segments
    out and freeing them up before the reblocker would otherwise run out
    of space.  Once things get cleaned up enough there should be enough
    free space to run the reblocker in normal mode.


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