Backup Exec 12.5 Compression

[areosol]

Hi Guys,

since a few days i´v a problem with our daily backup. We use a HP Tape Drive LTO4

Now the disk capacity is full and the backup needs a second disk. The data is not more than before.

I can see the compression rate is set to 1.0:1 which I dont think is right. The compression on each of the jobs is set to hardware and then software if no hardware is available. On old disk the compression rate is 1.2:1

I had this problem 8 month before, and then i update the tape drive firmware, this solve the problem. But now the drivers / firmware is up to date.

I don´t know what to do, anyone have ideas ?

thanks very much

[CraigV]

Hi,

1. Make sure you're using the Symantec drivers for the tape drive.

2. Check the tape statistics on the Media tab and see if there are excessive Hard Write Errors. This indicates either a problem with the tape/s or the drive.

3. Stop the BE services, download and install HP Library and Tape Tools (HP LTT). There is a compression test you can run that will tell you what compression you can get). Also run the device diagnostics to make sure there are no hardware issues on the drive itself.

Thanks!

[Larry_Fine]

http://www.symantec.com/docs/TECH50960

http://www.symantec.com/docs/TECH6076

[pkh]

It could be that you are compressing data which are already compressed.  This may result in more data than what you have started with.  See my article on this subject

https://www-secure.symantec.com/connect/articles/compression-short-explanation

You can test whether your data is compressible by using software compression.  To calculate the compression ratio, check how much data is written onto your tape and divide that by the actual amount of data backed up which can be obtained from the joblog.  The software compression ratio is roughly the same as that of the hardware compression.

[areosol]

Hi, i checked the tape drive and with the hp tape tools, everything is ok. The compressio test works. Now i start the scsi tracer, i set up a test backup and on the scsi tracer the value of the mode-selcect and mode-sense operations is 40 which means that the compression is not active. But in the device settings compression is enabled, í´m really confused. Also in the media libary the tape with the test backup show´s a compression 1.1:1

[Larry_Fine]

Now i start the scsi tracer, i set up a test backup and on the scsi tracer the value of the mode-selcect and mode-sense operations is 40 which means that the compression is not active.
But in the device settings compression is enabled, í´m really confused.

Be aware that BE turns compression on & off a bunch of times (I have no idea why), so it is vital to find the right line.

If you are sure that you interpreted the SCSI trace correctly, I would suggest trying to delete that job and re-create it.

If the tape is showing a 1.1:1 compression, then compression is actually on.

[areosol]

I tried a few tests.

When i backup a few folder on the server - the tape compress the files 1.2:1.

But the whole backup will still not compress.

So the compression in general will work – but why it doesn´t compress my normal backup ?

[Larry_Fine]

When i backup a few folder on the server - the tape compress the files 1.2:1.

But the whole backup will still not compress.

The 1.2:1 number is showing that compression IS working.  The fact that you are not getting compression on your whole backup is either due to a setting in that particular job or the data on the whole disk job is basically uncompressible.

[areosol]

This is really strane, before a few days, the backup finished on 1 tape. The settings didn´t changed.

Since there there is a bit more data but this should not be the reason.