Re: dump problems


the only indication I can see, is that one of the dump procs. is
waiting on
sbwait, and probably it's some deadlock, which is similar to what I
keep
seeing here, i'll try now with SCHED_ULE to see if it make a
difference.


I'm running SCHED_ULE on these already, if your not I guess it's not the
scheduler?

I can get it to 'work' by fiddling with the b flag (blocksize), which still
points to some timming/deadlock problem.
ie:
dump 0abf 64 /some/backup/file /file/to/backup
now works, but
dump 0abf 64 - | restore rbf 64 -
hangs as before. (i don't think the b 64 in restore is needed).

ok, it is time to look at the sources, this program has been around since the
beginin of time,
or at least since Unix V6 :-), and it has been hacked ever since. but now that
most of you never heard of 9track tapes, etc, I was wondering if there is a
point in hacking at
it again.
pros: dump/restore has never failed me till now.
cons: there are other programs tar/cpio/gtar/etc, but they each have their
nits.
so here are some questions:
- is the readers/writer split realy needed now? my guess it was put in in the
old
days to get tapes streaming - which is btw, what's not working.
- is it/will it be needed for ZFS? [dump is for ufs ...]

danny

Assumption:
Since dump was written, much has changed, and in the days of single-core/UP
the Caltech hack
(see /usr/src/sbin/dump/tape.c) works. On newer multicore hardware it will
enter into deadlock
and thus hang, specially if 'tape' is a file or pipe.

While I'm now putting on the surgical cap to dissect tape.c, any further
insight is welcome.

cheers,
danny



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