Re: [9fans] kenfs config? (was: OT: scsi sense error code hardware

[Axel Belinfante <Axel.Belinfante@cs.utwente.nl>]

> There's still the question of how to initialise the second device in
> the mirror-to-be.  I would have copyworm-ed f(w5w1) to f(w2).  I'm
> nervous that copying from cw0f(w5w1) may not yield exactly the same
> bytes as copying from f(w5w1).

Ok, thanks! I've tried looking at the code but (at this time of day)
initially only got more confused - /sys/src/fs/port/config.c:^wormof
seems not get the worm part of a cw, which is what I would expect it
to do (instead, it seems to take are of a cw within an fworm?).


I then realized that the copyworm code I run today was older:
  /n/sourcesdump/2003/0314/plan9/sys/src/fs/port/config.c 
it did copy the  f(w5w1) part of cw0f(w5w1) (the written blocks).

  copying worm from f(w5w1) to fw2, starting in 8 seconds
  limit 1505835
  copying worm
  fworm: read 0
  0 not written
  fworm: read 1
  1 not written
  block 20000 Tue Oct 17 15:57:26 2006
  [...]
  copied 1505835 blocks from f(w5w1) to fw2


Even earlier today I had tried the same with the slightly newer kernel
(code from march 14 2003) which I had patched to allow recover to work,
and then it not only did not give exactly the same bytes, but it failed:

  copying worm from cw0f(w5w1) (worm cw0f(w5w1)) to fw2, starting in 8 seconds
  devsize(cw0f(w5w1)) = 1505936
  fworm: read 0
  i/o error reading cw0f(w5w1) block 0
  panic: no blocks to copy on cw0f(w5w1)

I did not compare in detail, but the code seems to be essentially
the same as in the current version on sources.
my first superblock seems to be block 2 - that explains fworm: read 0?

related to the 'fworm of mirror' vs. 'mirror of fworms':
I guess that copyworm would not be able to deal with the case of
'cached worm where worm is mirror of fake worms' (or would it?)

Axel.
(turns out I have to redo the copy anyway because confused by
the big numbers of half-k and 4k blocks I chose a too small w2 disk
that won't allow much growth - but is was big enough to hold the
written part of f(w5w1) so I guess at least I have a backup)