USB Dat72 drive

[Dominic McHugh]

I have internal Dat72 USB - using NT Backup with hardware compression switch on I cannot backup more than 36GB

Tape Tools shows the drive is working perfectly - is there somewhere on the drive where we turn on hardware compression

Thanks

[Peter Godron]

Dominic,
welcome to the forums !
The native capcacity is 36Gb, so if your data does not compress well ...
Are you using the correct drivers and device files?

For more info see:
http://search.hp.com/query.html?charset=iso-8859-1&hpvc=sitewide&la=en&qs=&lk=1&rf=0&uf=1&nh=10&st=1&qt=HP+StorageWorks+DAT+72+USB+Internal+Tape+Drive&ocoldqt=Dat72&oc=501424


If you find these links of use :
http://forums1.itrc.hp.com/service/forums/helptips.do?#28

[Dominic McHugh]

Thanks Peter

All of the data are PDF documents does this mean we are already compressed and therefore the native 36gb will be the same as the compressed amount?

[Jaclyn Rothe]

A DAT 72 tape is a 36 GB native and 72 GB compressed.

Many thing can affect this ratio during back ups. Typically for a primarily text back up you will see 1.4:1 up to 1.8:1 ratio in a production environment.

Run the HP StorageWorks Library and Tape Tools Compression test and drive assessment test to determine if hard ware issues exsist.

DownLoad LTT 4.1:
http://h20000.www2.hp.com/bizsupport/TechSupport/DriverDownload.jsp?pnameOID=406731&locale=en_US&taskId=135&prodSeriesId=406729&prodTypeId=12169

If those test pass it is a bottle neck being created on your system that is affecting the ratio.

Slow throughput and old/bad media contribute to low compression settings because it takes time for the drive to write data to the tape, thusly the ratio average drops.

HP drives are designed to default to hardware compression on when the drive is powered on. Some software will disable this ratio in favour of software compression. Hardware compression algorithm is designed to run at a 2:1 ratio, but depending on the Data set your actualy back up ratio will be lower.

PDF fils, graphics, drawings and video are already compressed as much as they can. Text compresses well, exchange and databases will not be compressed during a back up.

[Jaclyn Rothe]

In addition... if you get 36 GB on a tape with all PDF files youa re at capacity becasue those files are alreayd in native sate and have compressed as much as they will compress.

If you back up 72 GB of texct you will fit is all on one media tape becasue it will at least compress by 50%, resulting in a 36GBback up.

[Dominic McHugh]

THanks Jacelyn

I have already tun LTT and it passed all tests no problem

I think you have just confirmed that the backup is fine and the PDFs are not compressible

[Peter Godron · Accepted solution]

Dominic,
thanks for the update. Can you please read
http://forums1.itrc.hp.com/service/forums/helptips.do?#28

Closing the thread whilst identifying the solution helps future problem resolution and awarding points rewards the efforts made by the contributors.

[Dominic McHugh]

Compression on backup has no effect on PDF files