restore command and 4mm tape

[ytakbob]

We use backup by name and restore for specific
data that we want backed up. We write approx 1.5 gig to the
tapes each night. blocking on the tapes are 0.
When attempting to restore from the tapes it takes an very long time to begin restoring...often more than an hour to
see it even find the data in the tape to restore.

by backup command is:
find ./bkp ./Arc ./hci ./hmu ./home ./tmp ./etc ./var/spool/cron/crontabs -fstype jfs | backup -i -v -q -f/dev/
rmt0

my restore is:
restore -xvdqf /dev/rmt0 ./hci/root3.5.4P

is this a normal amount of time for restores from tape ?
I have plenty of CPU and have even niced down the process.
ANy tuning suggestions would be appreciated.

Thanks.
Bob Schmid
bob_schmid@hmis.org
330-746-1010 ext. 1347

 

[bjverzal]

What version of DDS are you running ? It sounds more like a tape function delay versus an AIX system delay.

Bill.

 

[ytakbob]

How do you check DDS version ?
Bob Schmid
bob_schmid@hmis.org
330-746-1010 ext. 1347

 

[bjverzal]

The outside of the tape drive has "DDS2" or "DDS3" or "DDS4" on it.

 

[ytakbob]

THE tape is a DDS-2 120
the drive says DDS2
Bob Schmid
bob_schmid@hmis.org
330-746-1010 ext. 1347

 

[aixqueen]

Well there is this warning on the mksysb (which uses the
backup command for its backup)

WARNING: If the device blocksize is set to 0, mksysb will use a hardcoded value of 512 for the fourth image. This can cause the create and restore to take 5-10 times longer than expected.

I do not know which 4mm you have, but for the 12/24 4mm
they suggest using a block size?

With 'tar', use 262144 as the blocksize and use the flag -N512.
However, if you are using other command like 'backup' use the -b512.

http://www.rs6000.ibm.com/doc_link/en_US/a_doc_lib/aixbman/baseadmn/tape_attr.htm

 

[Guest_imported]

Variable Block Size ( 0 ) is desireable for sending
tapes to other sites for compatibility issues.

However, this does not do well for performance issues when restoring data from the same tape drive. IBM does have some specifications on block sizes and tape drives. It might be on their website. However, if you have the time,
You could experiment with block sizes set to multiples of 1024. Perhaps even 10240.

 

[ytakbob]

IT turns out that the device blocksizes were different.
The device where the tape was created was 0, the device reading the tape back in was at 1024.

I cahnged both to 0 and changed the -b parm of the restore and backup to 512. THings are going muh better.
Thank you all..you got me headed down the right track !

Bob Schmid
bob_schmid@hmis.org
330-746-1010 ext. 1347