Veritas-bu

[Veritas-bu] rman channels

2004-05-14 11:54:52
Subject: [Veritas-bu] rman channels
From: Mark.Donaldson AT cexp DOT com (Mark.Donaldson AT cexp DOT com)
Date: Fri, 14 May 2004 09:54:52 -0600
Despite their recommendation, what're you're probably seeing here is the
tape drive being "starved".

If you send too little data to the tape drive, then the drive must slow &
stop while more data is being accumulated.  The drive must then back up to
the end of the previous file and start writing the newly arrived data.  This
mechanical movement is very time consuming.

Adding more channels, and multiplexing at the drive, allows the drive to run
more efficiently by keeping the data flow to the drive constant.

I'll be you see this behavior more on your incremental RMAN backups more
than your full backups.  The incremental backups are going to
nickle-and-dime more than a full file backup, having a bigger chance of
starving your drives.

-M

-----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 Dave
Cecchino
Sent: Thursday, May 13, 2004 1:31 PM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] rman channels


Quick question,

I have a netbackup client that is configured to use 4 rman channels on a
sdlt tape drive , normally the filesystem backup runs about 27-30 meg
a/sec
however, 4 rman channels  only runs 4/mb sec , what gives?

I have setup the tape is slave true / and max files per set on the rman
rcv file, and some other tuning parameters, but can't seem to get the
channels to run faster than 4 /mb sec .




X

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