Datasheet

to the time it took in variable mode.
z AIX commands used. Depending on the AIX command used system backup/restore time may vary. Some tape drives
are sensitive to the delivery of data to the tape drive. Some applications take the blocksize and block the data block
into larger blocks for transfer to the tape drive. Some applications call this the blocksize, or the buffer size or blocking
factor. Whatever it is called you need to understand that some tape drives performance(data rate)is greatly effected
when the system sends small blocks of data. Try setting the tape drive block size to a large block size and large
blocking factor. You should test your application to see at what blocksize and blocking factor you get the best
performance for the tape drive you are using.
z Options chosen on the AIX commands. Some AIX commands have options that can improve performance. Refer to
the command reference for the commands you are using for the a description of the options.
z Buffer size(the size of the data transfer AIX uses to communicate with the tape drive). Often increasing the buffer size
will reduce the amount of system overhead required to transfer data to or from the tape drive. Reducing system
overhead often results in better performance and faster backup/restore times. Refer to the command reference for the
commands you are using to increase the buffer size.
z Tape drive compression setting On or Off. Not only does the option have to be set but if compression is selected the
tape drive and media must both support compression at the recording density specified.
z The ability of the data to be compressed. Some data, such as text data, is often highly compressible, graphic or binary
data is often not very compressible. Data that is more compressible will normally take less time to backup/restore
because of the use of specialized compression chips in some tape drives.
z AIX command compression option. Compressing data before sending the data to the tape drive may increase elapsed
time depending on the type of data and system activity. Data compression done by the drive will often result in faster
backup/restore, but due to other considerations such as network backup, etc., it may be faster to compress the data
prior to sending the data to the tape drive.
z Clean the tape drive with the approved cleaning method. If the tape head is not clean the drive may have to
rewrite/reread the data. To reduce the need to rewrite/reread data the tape drive should be cleaned as recommended in
the user manuals.
z The physical condition of the tape can have a impact on the time it takes to do a backup or restore. If a tape is not in
the best condition the tape drive may have to rewrite/reread data in order to do the backup/restore. This will this will
increase the time it takes to do the backup/restore.
z Increase the "blocking factor" to put out larger blocks of data which will reduce the number of times the tape drive
and the system have to communicate before writing or reading.
z Block size, can effect the time for backup/restore. Using large blocksizes may improve performance. Using small
block sizes can increase system overhead but before changing to a large blocksize it is necessary to be sure the user
application supports the larger blocksize chosen.
z Very long restore times due to blocksize. If a backup is done with a fixed block length then the restore should be done
with the same fixed block length. If a backup is done with a fixed block length and the restore is done with variable
block length, the restore may work successfully but it may take many more hours to restore than it took to back up the
data. The reason for this is that when AIX reads fixed block length data in variable block mode, a check condition is
issued by the tape drive on every read. AIX must interpret every check condition and determine the proper action to
take. This often will put the tape drive into a mode of reading that will require the tape drive to stop tape motion,
rewind the tape some distance, then start reading again. This will reduce the life expectancy of the tape and increase
the time it takes to backup data.
z Eliminate as many rewinds as you can. Do not write one file then rewind only to then space out to the end of the last
file written to write a new file. Use the .1 parameter on the rmt to reduce tape repositioning. Do not use this option
with the AIX mksysb command as mksysb handles tape positioning and rewind itself.
Device Driver/Robotics Driver(ATAPE)
Atape is the device and robotics driver for the 7332-005, 7332-110, and 7332-220.
Atape is the robotics driver for the 7331-205, 7331-305, 7334-410, and 7336-205.
Note: A minimum Atape level required for microcode download on the 7332-005 or 7332-110 is Atape 2.5.2.10.
To check the level of the Atape driver on a system do the following AIX command:
lslpp -l Atape.driver
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