Dear Kern,
in message <[EMAIL PROTECTED]> you wrote:
>
> All your reasoning is absolutely perfect up to this previous point. In
> looking at the Bacula error messages that you list above, it is always an I/O
> error writing a Bacula block that produces the problem. Once Bacula gets an
Argh... Thanks for pointing this out. So I always misinterpreted the
events.
> IMO, the source problem is coming when writing the buffers (a write()
> request)
> and not subsequent ioctl(WEOF). Also, between the write() that fails and the
> ioctl(WEOF), Bacula will issue some other ioctl(), which varies according to
> the OS. This ioctl() on a Linux machine, for example, is ioctl() MTIOCTOP
> with mt_op=MTIOCLRERR. In all cases, the purpose of this ioctl() between the
> write() and the ioctl(WEOF) is to attempt to clear any error condition in the
> SCSI driver to permit a valid EOF to terminate the Volume. On Linux, this
> may not be necessary, but on other OSes such as FreeBSD, the SCSI driver
> locks out virtually all I/O operations after a serious error.
OK.
> My best guess is that the problem is some sort of kernel SCSI lock race
> condition. As a consequence, I would recommend that you concentrate on
> writing lots of buffers as fast as you can, but from multiple processes,
> possibly to the same or different drives. In fact, you might try firing off
> several hundred write processes, and possibly a few read processes to another
> drive.
I will try that, but you just blowed my theory of why we see the
problem only with bacula, but never (yet) with any other program
writing to tape.
> When the SCSI driver complains about an unexpected disconnect, it is very
> likely because it either missed an interrupt or it issued a command at a bad
> time (i.e. a missing lock), or it overran the SCSI command queue.
I will try to run some tests...
Best regards,
Wolfgang Denk
--
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: [EMAIL PROTECTED]
"...this does not mean that some of us should not want, in a rather
dispassionate sort of way, to put a bullet through csh's head."
- Larry Wall in <[EMAIL PROTECTED]>
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