Re: [9fans] fossil+plan9: disk full revisited

[geoff@plan9.bell-labs.com]

Fossil does not eliminate duplicate blocks nor compress blocks, but
venti does both, and it is intended that serious use of fossil should
be backed with venti (which arenas should be stored on a RAID or
equivalent).  Using fossil without a backing venti gives the
equivalent of an `other' partition on Ken's file server: scratch
space.

The fossil write buffer needs to be only as large as the largest set
of blocks dirtied between dumps to venti, loosely speaking, so it can
typically be much smaller than the venti arenas backing it.  Edith,
our current primary file server, has 400GB of venti arenas, with
another 100GB available but not yet configured, and 34GB of fossil
write buffer, of which df reports 3% used.  87% of the arenas are
used.  (Yes, we have a new, larger file server ready to replace
edith.)