Its very similar to the way you would test to see if
Pasta is done. The old Italian way (at least an old
Italian told me this) is to throw a piece of pasta
against your refrigerator and see if it sticks...sorry,
must be the holidays...
No, no formula just the disclaimer - Your mileage may
vary. MPX was implemented to support slower clients or
networks being backed up to fast tape drives. There
are several factors that I would pay attention to when
increasing my MPX values.
First: Its an attribute of your storage unit, this is
how many streams per drive will you allow.
Second: Its an attribute of the schedule, how many
streams per schedule will this class allow
Third: Its an attribute of the class, Multiple
DataStreams AND Max jobs / Class (this should be
greater than 1)
Another item to look at is the max jobs per client
(default is 1) which is part of the global attributes.
You want to be careful with this because if this value
is higher than 1 and you are backing up a slower client
and MPX is enabled, you may see diminishing returns in
your performance.
What i have done is enable MPX on the storage unit
(DLT) up to 6/drive.
then on the schedule I would start small, say 2 /
schedule in a given class. Also making sure your max
jobs/class is greater than 1 and Multiple Datastreams
has been checked.
Test, evaluate and reconfigure until you have reached
your optimum performance objective.
Caveat: A multiplexed image does *NOT* maintain a tar
compatible header. This means that you will not be
able to use the modified version of tar that is shipped
with NBU to read this tape. In order to do this you
must de-multiplex the image using bpduplicate to
accomplish that task.
I hope this information is helpful.
david chapa
Quoting "Laszlo, Kathy" <KLaszlo AT petro-canada DOT ca>:
> Hello,
>
> Can anyone tell me if there is a formula or method to
configuring the MPX
> factor for each class?
>
> We are having a problem completing our backups on
time (we are out by 5
> minutes).
> I'm hoping by playing with the MPX variable, I can
get the 5 minutes back.
>
> Thanks,
> Kathy
>
> _______________________________________________
> Veritas-bu maillist - Veritas-
bu AT mailman.eng.auburn DOT edu
>
http://mailman.eng.auburn.edu/mailman/listinfo/veritas-
bu
>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
David A. Chapa
Consulting Manager
DataStaff, Inc.
847 413 1144
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