WORD TO THE WISE:  Do the math before you set your MPX value...What is your 
network speed, what is your drive speed, how many MPX before you start seeing 
diminishing returns.  If you are sending too many MPX streams to the drive you 
will end up with WAITING FOR EMPTY BUFFERS in your bptm log on your media 
server, thus meaning that your drive can't keep up.  Alternatively speaking if 
you have WAITING FOR FULL BUFFERS, then perhaps you can increase your MPX 
value, but remember balance is the key when you look to tune your environment.

Dave:  The question about streams, it would depend if he has implemented MDS 
(Multiple Data Streams), if he had, then each Drive would potentially be an 
individual stream.  

Simon: This would only be a potential problem if you have modified the default 
value (1) MAX JOBS PER CLIENT to > 1.  If you do that, you really need to be 
careful.  Its been my experience that NT/2000 (single processor Intel boxes) 
are less likely to push multiple streams of data to the media server.  Your 
mileage may VARY box to box...

David

Quoting David Markham <dave.markham AT icl DOT net>:

> I think you should set it to 8 if you want all clients to backup to 1 tape,
> and watch what happens. I've  just had a thought which someone may want to
> clarify. As there are 2 drives beeing backed up does that mean theres 2
> streams per client, or just the 1 for the job?
> 
> If its the first then you may need to set the mpx to 16 to get the schedule
> to backup to one drive.
> 
> Dave
> 
> -----Original Message-----
> From: WEAVER, Simon [mailto:Simon.WEAVER AT astrium-space DOT com]
> Sent: 21 May 2002 06:24
> To: 'dave.markham AT icl DOT net'
> Cc: veritas-bu AT mailman.eng.auburn DOT edu
> Subject: RE: [Veritas-bu] Multiplexing
> 
> 
> Thank you all,
> So Dave, if I have a Backup Policy with 8 clients and they all backup the
> C:
> Drives and E: Drives, what Multiplex number should I use? At the moment I
> have set it for 4 to see what happens.
> 
> Thanks
> 
> Simon Weaver
> NT Domain Administrator
> Ext. 5544
> Tel: 02392-705544 (Direct Dial)
> Simon.Weaver AT Astrium-Space DOT com
> 
> -----Original Message-----
> From: David Markham [mailto:dave.markham AT icl DOT net]
> Sent: 20 May 2002 03:19:PM
> To: WEAVER, Simon; 'Dave High'
> Cc: veritas-bu AT mailman.eng.auburn DOT edu
> Subject: RE: [Veritas-bu] Multiplexing
> 
> Yes if they are backed up from the same schedule, and they use tapes all
> from the same pool.
> 
> You will need to make sure the max mpx per Drive is set higher than 2 also.
> 
> Dave
> 
> -----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 WEAVER,
> Simon
> Sent: 20 May 2002 14:56
> 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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> Gunnels Wood Road
> Stevenage
> Hertfordshire
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> The views of the author may not necessarily constitute the views of Astrium
> Limited.
> Nothing in this email shall bind Astrium Limited in any contract or
> obligation.
> Astrium Limited
> Gunnels Wood Road
> Stevenage
> Hertfordshire
> SG1 2AS
> 
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