Ultrium 960 hardware compression RHEL

[caterpillerrbcmail.ru]

Hi.
I have RHEL4 up 4 x86 and Ultrium 960 with S/N HU10702WJ1, Firmware Rev : G54D/Standalone.
I install TapeWare on my RHEL, set it to use hardware compression, but can’t write more than 412 GB to the original media 400/800Gb,
I try to write my data with TAR, tar cvf /dev/st0 /* and write 412GB, bun no more!
Then, thinking that hardware compression was not used? When I was writing to media,
i’m download hp_ltt and test my Ultrium 960. Test show that Hardware compression work correct with 2.62:1 ratio
In test I see that tool “hp_ltt” use /dev/sg0, but TAR can’t write to this device!!!!!!!!!
Help me please, how I can write my data (oracle base) with hardware compression with TAR or other soft!

[Marino Meloni_1]

If you can store 412GB, this mean that the compression is working, usualy if compression is not working you never go over the natice cartridge capacity.
If you want to test the funtion, and have some space on disk, you can use LTT and create data with know compressibility (using system performance pre restore test) then you should create lets says 600 GB data with 2:1 compressibility ratio.
then save them to the tape, if you can store the data, the compression is working.
You should also take into account that the capacity of the cartridge may be reduced due to other factor, bad blocks, and some time bad communication, and also slow data source.
If the tape is streaming at full speed, probably you have no one of the suggested problems, if the speed is less than the minimum streaming of the drive, you should alsoinvestigate in that direction

[Richard Bickers]

Another thing you can try is to run the back up and then afterwards use LTT to pull a support ticket.

Under drive->performance you will find the compression ratio that the drive actually achieved with the data. You can also see that compression is enabled under drive->configuration.

The 400GB figure stated with the media already allows for some data loss due to error rate degradation. You might get an extra 5% if everything is perfect so 412GB is within that range. It may be that you've not got DC switched on or your data really is uncompressible but that's most unusual for databases.

Feel free to post the ticket if you'd like us to look through it. There's a lot of other info in there which can be useful too.

Good luck, Richard. (LTT team)