Compression Dropped

[rgomez]

Hi,

After a few tests I was able to check that my backups are not being compressed. I've done the 2GB txt file text with hardware compression and got about 34:1 compression ratio.

Backing a few User Folders with regular Word, Excel, Images, etc files with around 230GB (just for testing porpuses) it shows 372GB of 781.5GB used, but only 208GB of data is shown on the software. Running bigger Backup Jobs the server swaps tape at around 500GB of data.

I'm backing up from a Windows Server 2008 R2 x64 server to Backup Exec 2010 R3 - LTO4 Drive on MSL2024 Libary

Things done prior to testing:

- Disabled AV on source server (not installed for backup server)

- New SCSI Cable

- Different SCSI Controller

- Different Server Hardware

- Fresh Windows Installation

- Fresh Backup Exec installation (using trial)

- Multiple Tapes tested

I'm changed from hardware to software compression and it's running the job right now, but I'm pretty sure result will be the same. What might be the cause for this? Has been a working enviroment for around 2 years, nothing changed.

An interesting thing might be that with Backup Exec 2015 I can write 780GB to each tape.

Best Regards

[rgomez]

Now I'm really confused. After running the Same Job only with Software Compression I got:

The Byte Count is exactly the same for both Jobs but the Software compression took 10 more minutes.

186.4GB of Data and a 413.4GB of 781.5GB on the Capacity graph.

against

208.2GB of Data and a 372.0GB of 781.5GB on the Capacity graph (Hardware Compression)

My guess would be that It's compressing but not showing correct data to the Software and it's swapping tape before it's full? Is that possible?

[rgomez]

Here is the Hardware Compression Tape:

And the Software one:

[pkh · Accepted solution]

Your test with the text file file shows that hardware compression is working correctly for your tape drive.

If your data fail to compress, then it is the nature of the data.  For example, if you are compressing data which is already compressed, like zipped files, pictures, movies, etc, then you may end up with more data than you started with.  See my article below

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

The other possible reason is that your tapes have a lot of errors, thus reducing its overall capacity.

[Larry_Fine]

If you are not able to even obtain the native capacity of your tapes, then you may have a clogged head in your tape drive.  See this technote for more info.  As this is hard to troubleshoot, you will probably need to get your hardware vendor involved.

http://www.symantec.com/docs/TECH193200