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DTL 8000

castro_2
Regular Advisor

DTL 8000

I want to kwon which is the block_size in DTL 8000 and there is a way to change it.
Thanks
Regards
9 REPLIES
A. Clay Stephenson
Acclaimed Contributor

Re: DTL 8000

That question really has no meaning. Blocksize is the sole responsibility of the application itself. In fact, the application might use variable blocking so that 1 block might be 1024 bytes and the next 256KB and the next might be 64 bytes.

Some tape commands allow you to specify a blocksize but you can always use the dd command to reblock data more to your liking.
If it ain't broke, I can fix that.
Michael Schulte zur Sur
Honored Contributor

Re: DTL 8000

Hi,

what os is the machine running, it is connected to?

Michael
castro_2
Regular Advisor

Re: DTL 8000

Hp-uX 11.00.
Thanks
Regards
Michael Schulte zur Sur
Honored Contributor

Re: DTL 8000

Hi,

if I am not mistaken, then there is no permanent way.

tar for examples has the b option to change blocksize.

Michael
Curtis Ballard
Honored Contributor

Re: DTL 8000

What application are you using? tar? dd? Data Protector? As indicated in the earlier postings there is no hard block size for DLT on HP-UX. For Windows based systems it is usually stuck at 64K because that is the default maximum block size but HP-UX doesn't have that problem. On HP-UX I like to use a 256K block size.
Vincent Farrugia
Honored Contributor

Re: DTL 8000

Hello,

As far as I know, the recommended block size for DLT8000 is 32K. This value comes from experimentation. Really, it depends on the application, though. For "average" purposes, though, 32K is the recommendation.

HTH,
Vince
Tape Drives RULE!!!
David Ruska
Honored Contributor

Re: DTL 8000

Vincent,
A while back we did some testing on block sizes, and found that even 32K had some degradation (particularly with newer firmware >=V59 which apparently added more per-block overhead).

From Quantum's FAQs (#D67 on slow throughput):
"Check the blocks size assigned to the tape drive and make sure it is between 64k to 128k from the backup application device configuration."

So, 32K probably isn't bad but going larger might help.
The journey IS the reward.
Vincent Farrugia
Honored Contributor

Re: DTL 8000

Thanks :-)
Tape Drives RULE!!!
David Ruska
Honored Contributor

Re: DTL 8000

You're welcome, your highness.

(sorry to nitpick)
The journey IS the reward.