TITLE    : Howto increase Magstar tape drive performance.
OS LEVEL : AIX
DATE     : 09/06/2000
VERSION  : 1.0

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When a Magstar tape drive is added to a system, the block size is set to
zero by default. The performance of the Magstar can be increased by
altering the block size and blocking factors of the archive command.

Note:	ensure that you have the latest version on the atape.driver installed
	on you system. The latest drivers can be found at
	ftp://index.storsys.ibm.com/devdrvr/AIX/

In the tests below a 4 gig filesystem was archived using different 
tape drive block sizes and cpio blocking factors :-


(1):	chdev -l rmt1 -a block_size=0
	rmt1 changed
	time find /data -print | cpio -ocB > /dev/rmt1
	7926820 blocks

	real    34m58.88s
	user    1m46.80s
	sys     2m17.78s

(2):	chdev -l rmt1 -a block_size=1024
	rmt1 changed
	time find /data -print | cpio -ocB > /dev/rmt1
	7926820 blocks

	real    2h34m0.89s
	user    1m41.24s
	sys     2m17.89s

(3):	chdev -l rmt1 -a block_size=1024
	rmt1 changed
	time find /data -print | cpio -ocC1024 > /dev/rmt1
	7927808 blocks

	real    2h40m20.00s
	user    1m42.12s
	sys     1m28.74s

(4):	chdev -l rmt1 -a block_size=262144
	rmt1 changed
	time find /data -print | cpio -ocC1024 > /dev/rmt1
	7927808 blocks
	
	real    17m57.45s
	user    1m39.93s
	sys     1m29.49s


Tests conducted using an RS6000 43P model 150 and a Magstar MP 
3570 model B00.