There was a point about thru-put in one of the postings.  Just to clarify,
MPX will increase your aggregate throughput...not the throughput of each
individual stream...

MPX is a great way to keep your drive streaming and avoids the
"shoe-shining" that occurs when it has to wait for data...

Oh and YES, MPX will write as many streams as you have configured at your
STORAGE UNIT and the SCHEDULE of the Backup Policy in question until the
tape is full.

It is also worth noting that when you enable MPX, you forfeit the tar
compatible header that is otherwise found on the NBU tapes.  In other words,
if you wanted to "get data" from this tape using the modified version of gnu
tar that is shipped with NBU, you would have to first de-mux the image, and
this is done using bpduplicate.

Your mileage may vary regarding performance so it may behoove you at some
point in your testing/production of MPX to look at the possibilities of
tuning...

Okay, I'm done.

David

<><><><><><><><><><><><><><><><><><><><>
David A. Chapa
NetBackup Consultant
DataStaff, Inc.
http://www.datastaff.com
847 413 1144
---------------------------------------
http://www.NetBackupcentral.com

-----Original Message-----
From: veritas-bu-admin AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu]On Behalf Of Barda, Boaz
Sent: Monday, May 20, 2002 9:14 AM
To: 'WEAVER, Simon'
Cc: 'veritas-bu AT mailman.eng.auburn DOT edu'
Subject: RE: [Veritas-bu] Multiplexing


Hi,

Lets make it clear:
If you want to backup all your clients in that schedule to one tape you must
set the streams allowed on that tape to at least the amount of streams that
schedule produces.
I.E. If you have 16 PC clients with C and D drives and you have
ALL_LOCAL_DRIVES in the files to back up then you need the tape to allow 32
MPX.

That will make your backup use only one drive for that job.
BUT.... (there is always a but) it will not be time efficient. It will
probably have more data flow then the TAPE can handle.
And there will be a lot of IO wait time wasted.
Secondly 32 MPX per drive may result in media write errors and other
annoying errors. Personally I configure MAX 6 MPX per LTO drive.

Hope it helped,
Boaz.
-----Original Message-----
From: WEAVER, Simon [mailto:Simon.WEAVER AT astrium-space DOT com]
Sent: Monday, May 20, 2002 4:56 PM
To: 'Dave High'
Cc: 'veritas-bu AT mailman.eng.auburn DOT edu'
Subject: RE: [Veritas-bu] Multiplexing


Hi Dave / Everyone
My apologies, I probably did not make myself clear.

Yes I am not looking for a way to put more data onto the tape (Obviously if
it his its 100GB Limit, it will get a new tape and I fully understand that).
But I think the point being made is that I want these 8 clients to utilise
one tape until it is full, and then move onto another tape.

Here is my point. We have a lot of jobs with a lot of clients (16 per backup
policy) and they have a lot of streams. I just wanted to clarify that if I
increased the multiplexing number from 2 to a higher number, would Netbackup
try to place the Data onto the same tape in a single drive? At least until
the tape becomes full :)

Simon Weaver
NT Domain Administrator
Ext. 5544
Tel: 02392-705544 (Direct Dial)
Simon.Weaver AT Astrium-Space DOT com

-----Original Message-----
From: Dave High [mailto:Dave.High AT veritas DOT com]
Sent: 20 May 2002 02:37:PM
To: WEAVER, Simon; 'veritas-bu AT mailman.eng.auburn DOT edu'
Subject: RE: [Veritas-bu] Multiplexing

Simon,

Multiplexing will not help you write "more" info to a tape. A tape can hold
a specific amount of data based on tape format and compression. Once it is
full, it is full. Using Multiplexing can help you use less tapes during a
backup run since more streams are filling up a single tape rather than
loading three tapes and writing to them, but NetBackup will continue loading
and using a tape until it is full, then it will move on to a new tape.

Also, on other thing I wanted to point out about the bpexpdate command is
that it does NOT "erase" a tape it simply removes the NetBackup Catalog
reference to that tape and allows it to be overwritten. The data is still on
the tape until it is overwritten. The only reason I bring this up is for
security reasons. If you need to get rid of the data on the tape, you need
to bpexpdate it, then run a big magnet over it to wipe the data.

Hope this all helps.

dave

-----Original Message-----
From: WEAVER, Simon [mailto:Simon.WEAVER AT astrium-space DOT com]
Sent: Monday, May 20, 2002 5:45 AM
To: 'veritas-bu AT mailman.eng.auburn DOT edu'
Subject: [Veritas-bu] Multiplexing

Firstly, Thank you all for your help with BPEXPDATE. I am glad I am getting
this right now :)

I have one small question about Multiplexing. On the Netbackup PDF's (which
is what I am using) it says you can specify the number of jobs that can
multiplex to a single tape drive! (Words to that effect).

My question is this: I have a backup policy with 8 clients listed. Within
this backup policy I have specified to backup All Local Drives for these 8
clients. I want to use as less tapes as possible (I use 100GB HCART Tapes).
If I increase this Multiplexing number, does it mean that more data will be
written to a single drive in a tape?

We use an ADIC Scalar 100 which consists of 3 tape drives. Because I have no
more slots available to place blank tapes, I was kind of hoping that using
this Multiplexing option will help retain more data on a single tape!

Am I right, or am I reading this incorrectly.!

Thank you

Simon Weaver
NT Domain Administrator
Ext. 5544
Tel: 02392-705544 (Direct Dial)
Simon.Weaver AT Astrium-Space DOT com

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Nothing in this email shall bind Astrium Limited in any contract or
obligation.
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Hertfordshire
SG1 2AS
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