Veritas-bu

[Veritas-bu] multiplexing & Confused

2004-12-29 20:39:25
Subject: [Veritas-bu] multiplexing & Confused
From: Dean <dean.deano AT gmail DOT com> (Dean)
Date: Thu, 30 Dec 2004 12:39:25 +1100
> My questions are
> 
> 1) If i run the policy how many jobs will be active
> and how many will be in queue

 For each client, there will be one job per filesystem/partition (5 in
your case), plus one for "System_State". You will have up to 8 active
jobs per drive, but no more than 4 from one client active at the same
time (max job per client=4). You only have one client, so only 4
streams will be active. All four will go to one tape drive (stu mpx =
8).

> 2) Will the multiplexing(8) will effect for only one
> drive? or both drives

8 streams per drive in the st unit. If you have 2 drives, you can run
up to 16 streams concurrently.


> 3)Also if some one explain this terms ( Multiplexing,
> Multiple DataStream,)

Hmm... I think of it this way:
Multi-streaming is at the client - reading the data from the client in
multiple streams, multple jobs in the activity monitor.
Multi-plexing is at the tape drive. Multiple streams are written
(multiplexed) to the tape drive concurrently. They could come from one
or several clients.

> 4) What is difference between setting MTX value in
> storage unit and policy
> schedule? 

MPX at the storage unit is an overall setting for those tape drives.
MPX in the policy is just for that policy. You might have a policy
with MPX of 32, but the storage unit MPX is only 4, so no more than 4
streams will run at once, the rest will queue. I usually set all
policies to max MPX = 32 and then control it all at the storage unit
level.

> How the maximum jobs per client setting will
> affect this??

Max jobs per client is how many jobs (streams) will run concurrently
from one client. In your example, each client will generate 6 streams,
but only 4 will run at a time, the others will queue.

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