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README for hptapeperf
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hptapeperf is a tape performance testing utility that sends data
from memory to a tape device. The advantage of this is it allows
the administrator to determine the speed of the device in
absence of the data source, which may distort the true performance
capability of a high performance tape drive.

There are a number of command line arguments:

  -b <blocksize>
                 Specifies the blocksize in bytes to be written to tape.
                 Typical values are: 32768 (32KB), 65536 (64KB).
                 Defaults to 65536.

  -o <device>
                 Specifies the tape device to write to, examples are:
                 /dev/rmt/0mnb      HPUX
                 /dev/rmt/0cbn      Solaris
                 /dev/nst0          Linux
                 No default, must be specified.

  -i <type>
                 Specifies the data pattern to be written to tape,
                 either of:
                 -i 2              
                 -i 3             
                 Defaults to 2.

  -c <count>
                 Specifies how many blocks of <blocksize> to write to the 
                 tape device per write.
                 Defaults to 16.

  -r <reps>
                 Specifies how many writes/reads to perform.
                 Defaults to 4096.

  -R
                 Enables the readback test after writing data to the
                 device (reports read performance in addition to write
                 performance in MB/sec).
                 Defaults is not to readback.

  -v 
                 Be more verbose about what's occurring.
                 [Warning - should be used sparingly as may impact 
                 performance observed due to output of 'w'/'r' per block
                 written/read]

At a minimum, -o <device> should be specified.

Typical full usage would be:

  hptapeperf -i 2 -o /dev/rmt/0mnb -b 65536 -c 16 -r 4096 

Which would utilise the tape device /dev/rmt/0mnb, setting the blocksize
to 64KB (65536 bytes), and transferring (64KB * 16 = 1MB) per write to the
tape device. Overall transfer size is thus (4096 * 1MB) = 4GB in this
instance. 

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Notes:

The compression patterns are at those compressibilities for the DC
engine within HP LTO tape devices (ALDC), other tape devices may find them
more/less compressible depending on the algorithms they utilise. 

An earlier release had to have files twoto and threeto present in the
current working directory. This release eliminates that requirement and
generates the pattern in memory then sends it to the tape device.

11/03/02
