LTO3 drive cannot save 533 GB

[Richard Bickers]

Hi Jose,

It looks to me like the compression is working OK. You're giving it 533GB and it's compressing down to 273GB. The mystery to me is why it's hitting EOT (end of tape) at that point.

It's true that's not HP media you're using as HP LTO3 media is yellow. Should work OK with other vendors though.

Marino's method should work well for creating known compressible data on your disk which you can then back up onto tape.

It would be nice to eliminate the application from the issue. The only other method is to use the Device Performance test but that only goes to 16GB max. It will at least show you compression is working for that amount. Sounds like we should increase that value in future...

We might learn more from the ticket. At least we'll know how well your drive has been writing data.

[Richard Bickers]

One more thought... On Windows we recommend customers disable RSM (Removable Storage Manager) which polls the drive every few seconds and which, in turn, causes a flush of data to tape. In most cases this impacts performance because each one requires a subsequent append but if performance is already low it's actually capacity that takes the hit due to the wasted dataset space from each flush.

If there's something similar going on with your system it could have a serious effect on capacity. Can you check if there are any 'background' services that might be talking to the drive?

[Jose M. del Rio]

It' definitely an fbackup issue.
We have tried with dd and everything has gone OK:
- Tape Capacity Log
- Main Partition Remaining Capacity :120182 (MB)
- Main Partition Maximum Capacity :400308 (MB)
It seems fbackup is wasting a looot of space.
We will be playing with fbackup parameters (blocksperrecord, checkpointfreq...).
Or it is maybe related to "fast search marks"...

[Jose M. del Rio]

I forgot to mention we have been saving daily about 520 GB to the tape with no problem.
Our data grown recently to 533 GB and that was when the problem showed up.
So we suspect it's a matter of size.

[Richard Bickers]

Glad you found the culprit. You can't really beat a 'proper' application for effective backup - both for capacity and performance - but that does mean spending money.

If you're interested, the ones HP recommends can be found from our compatibility web pages www.hp.com/go/connect. Follow the link on tape backup and then software compatibility.

For HP-UX it lists:
- CA BrightStor ArcServe 11.x
- HP Data Protector 5.5
- Native TAR, CPIO (wasn't expecting to see these!)
- Symantec Netbackup 5.1
- Legato Networker 7.2
- HP IgniteUX 2 stage boot from tape

If you get to the bottom of the fbackup issue it would be great to post it back out to the forum. You can't be the only one... Thanks.