On Sun, Sep 16, 2001 at 05:22:14PM -0700, Matthew Jacob wrote:
> 
> Do you, perchance, for some really strange reason, use the *block* interface
> to the tape drive? I have to admit that my experiences with things wedging up
> come from some inadvertant testing with the block version (repeat inf: blush).
> 
> I rather suspect that any soft error which causes a check condition will
> reduce streaming. We may need to rethink whether or not all errors should be
> done by the completion thread.

No, I don't use the block device.  And my kernel isn't *reporting* a soft
error on the tape drive ever.  But, I note that:

1) The clock slippage *may* be limited to the end of the backup runs; I
   can't shake the feeling that I've seen it otherwise, but... it may
   only happen when I do the close(); however, it does happen with either
   the rewinding or non-rewinding device.

2) Indeed, I *cannot stream* my DLT8000, though it's being fed via a
   large circular buffer (either the one in Amanda, "buffer" from pkgsrc,
   or a circular-buffer writer of my own) from large sequential files that
   are striped across two IDE disks that can read from them through the
   filesystem at >50MB/sec and is the *only* device on an Advansys LVD
   SCSI adapter.  The data rate rises gradually to about 12MB/sec over the
   course of about 30 seconds, then the tape mechanism stops, the data rate
   falls off, then picks up again.  Quantum have no idea what's going on
   and have advised me to wait for them to fix the drive's variable-speed
   write feature with new firmware.  However, they say that if I can hand
   the drive 12MB/sec of data, it ought to stream indefinitely, much less
   50MB/sec.

Is there a soft error for "internal buffer full" or some such that might be
causing this kind of lossage?

-- 
Thor Lancelot Simon	                                      tls@rek.tjls.com
    And now he couldn't remember when this passion had flown, leaving him so
  foolish and bewildered and astray: can any man?
						   William Styron