Re: Best Backup Blocksize for 110SDLT Tape?

From: Tom Simpson (thomas.simpson1_at_nospam.comcast.net)
Date: 03/05/04 

Date: Thu, 04 Mar 2004 23:53:05 GMT

Thanks for the clarification. That number seemed way bigger than I
expected...that's why I questioned it.

I was trying to point out a possible origin for the old system manager's
aversion to larger block sizes. I doubt it has anything to do with problems
on newer drives...

One other (obvious) thing that was not pointed out here is that if you are
writing small save sets (smaller than your selected block size), the tape
has to write the whole block, so space and time may be wasted in that
situation. On image backups, that's not an issue.

I normally use the 32K block size to avoid problems when I copy save sets.
I have had many problems recovering data from multi-volume 9-track tapes
(using VMS 7.2-1), but never DLT tapes. So far, I don't have a multi-volume
SDLT backup, so I can't speak to that situation.

Regards,
Tom

"John Santos" <JOHN@egh.com> wrote in message
news:1040303234647.15727A-100000@Ives.egh.com...
> On Thu, 4 Mar 2004, Tom Simpson wrote:
>
> > One factor (especially with older tape drives and lower bit densities)
that
> > could be a problem is the physical length of tape it takes to write a
large
> > block of data. Last time I checked, the standard distance from the EOT
> > marker to the physical end-of-tape is roughly 15-20 feet. If 20 feet is
not
> > enough space to fit a data block, then the backup could fail. The
typical
> > symptom would be the tape runs off the end of the reel (on 9 track tapes
for
> > example).

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