On Fri, Sep 07, 2001 at 05:59:59PM +0200, Manuel Bouyer wrote:
> On Sun, Aug 26, 2001 at 09:13:39PM -0400, Thor Lancelot Simon wrote:
> > 
> > On several different machines, all with "options NTP" and ntp4, with
> > several different SCSI host adapters, both in 1.5 and in current with
> > thorpej-scsipi, I've noticed that if I push the 'st' driver hard, two
> > things happen:
> > 
> > 1) Output periodically pauses; the result is that the tape doesn't stream
> >    for more than perhaps 30 seconds at a time.  Whether I have four striped
> >    SCSI disks feeding a DLT8000 on a separate SCSI bus or a single IDE disk
> >    feeding a DLT2000XT, I can sustain well above the drive's continuous
> >    write rate for some time, but inevitably there's a pause that causes
> >    the tape to stop streaming.
> > 
> > 2) ntpd periodically must adjust the clock by about 0.5-1.5 *seconds* while
> >    the tape drive is in use.
> 
> Do you see complete wedges of the machine (keyboard input stops, etc ..) ?

Only occasionally, and always during a tape error condition; Matt may have
actually more-or-less explained that problem, too.

Normally, if I do something like write a few GB of data to tape, everything
proceeds as normal during the backup, but once it's over NTP adjusts the
clock by 0.5-1.5 seconds at once.

Actually, it may occur during long backups, too; I can't remember.  I'll do
some more testing tonight.  If it happens _only_ at the end, that might
implicate the close routine (rewinding, perhaps) though I can't see how.