[9fans] venti

["Russ Cox" <rsc@plan9.bell-labs.com>]

[A side note:

A number of people have reported not being able to connect
to sources.cs.bell-labs.com.  Our external DNS seems to be
very slow.  I'm not sure exactly what's wrong, but until we
fix it you can use:

	echo 'dom=sources.cs.bell-labs.com sys=sources ip=204.178.31.8' >>/net/ndb
	echo -n refresh >/net/cs

as a workaround.]

There's a new command venti/wrarena, which complements rdarena.
 From ventiaux(8):

          venti/wrarena [ -o fileoffset ] [ -h host ] arenafile [
          clumpoffset ]

          Wrarena writes the blocks contained in the arena arenafile
          (typically, the output of rdarena) to a Venti server.  It is
          typically used to reinitialize a Venti server from backups
          of the arenas.  For example,

               venti/rdarena /dev/sdC0/arenas arena.0 >external.media
               venti/wrarena -h venti2 external.media

          writes the blocks contained in arena.0 to the Venti server
          venti2 (typically not the one using /dev/sdC0/arenas).

          The -o option specifies that the arena starts at byte
          fileoffset (default 0) in arenafile . This is useful for
          reading directly from the Venti arena partition:

               venti/wrarena -h venti2 -o 335872 /dev/sdC0/arenas

          (In this example, 335872 is the offset shown in the Venti
          server's index list (344064) minus one block (8192).  You
          will need to substitute your own arena offsets and block
          size.)

          Finally, the optional offset argument specifies that the
          writing should begin with the clump starting at offset
          within the arena.  Wrarena prints the offset it stopped at
          (because there were no more data blocks).  This could be
          used to incrementally back up a Venti server to another
          Venti server:

               last=`{cat last}
               venti/wrarena -h venti2 -o 335872 /dev/sdC0/arenas $last >output
               awk '/^end offset/ { print $3 }' output >last

          (Of course, one would need to add wrapper code to keep track
          of which arenas have been processed.)

Russ