Hardware compression

[Tim_Stainton]

I am using an external HP SCSI C7438A Dat72 drive on Windows SBS 2003 using Backup Exec 10 SBE. When installing I chose to use the Backup Exec drivers, and had not previously installed the HP drivers which came with the tape backup unit.

Everything works fine, but selecting to use hardware compression appears to be no different than selecting no compression at all and I can get no more than about 33GB on the tape and I am using standard HP Dat72 tapes.

I have loaded the latest HP LTT software, updated to the latest firmware, enabled hardware compression and the tests show that I am getting 2.2:1 compression.

What I refuse to believe is that with a wide range of system files, Exchange files and general Word and other database files being backed up, that the actual compression on a real backup can be 1:1. There has to be something which although Backup Exec appears to allow me to use hardware compression, in fact it is not.

Can anyone suggest a way forward or further tests I can carry out?

Thanks.

[Keith_Langmead]

Have you confirmed that the drive actually does hardware compression? I know it's unlikely it wouldn't these days, but you never know, I have seen some other drives which didn't, though they were generally older ones like DDS3/4 drives.

Have you tried using software compression instead and see what results you get then?

[Tim_Stainton]

Hi.

All the documentation says it supports hardware compression as does the configuration utility available for it, so I must assume it does. Interestingly, using software compression didn't seem to make much difference either.

Incidently, I need to make sure I am reading the facts correctly. I am going to the device in Devices and on the right-hand side it shows the media in the drive, which is the one I have been testing with. Right-click and select Properties and up comes the Media Properties box and on the Statistics tab are the figures I have been looking at.

Having just done a test full overwrite backup, it shows Used capacity 18.1 BG, Total capacity 33.8 GB Compression ratio 1.18:1 and Bytes written 18.9 GB. How are these figures arrived at?

Thanks.

[Ken_Putnam]

Real World compression ratios are generally more in the 1.2-1.3:1 range that 2:1, so it looks like the drive may be working correctly if you are getting 1.18:1

[Tim_Stainton]

I will try a few other tests and see where it goes.

Thanks.

[Steve_Hammes]

Since installing BE service pack 3 (on 10.1d) my compressions rates have are at 1:1 or below, when they had been at least 1.50:1 or better. I have posted this elsewhere in this forum, but haven't received any replies yet.

I even tried software compression on one backup with similar results. I 'm hoping someone out there can give us some answers, support here seems very minimal.