HP SPS_DAT 320 USB External Tape Drive

[ahmad barakat]

Hi ..
I have SPS_DAT 320 tape drive and i have a problem with compressed data ,i can't take a backup more than 150 GB size.

thanks..
Ahmad

[Torsten.]

You unlikely have an USB tape connected to a hp-ux system, right?

however, if your data is already compressed, around 150GB is the maximum.

[ahmad barakat]

dear

please note i worked under windows OS ,and my data size is 240 GB And I take my backup by hp data protector 6.11 ,i can't complet the backup i recived mount request msg on 150 GB

[Bill Hassell]

A DAT 320 will *NOT* store 320 GB of data. The 320 GB number is a marketing ploy that began more than 20 years ago when compression was first offered DDS (misnamed DAT) drives. The compressed value assumes that the data being backed up is highly repetitive, things like text files with trailing spaces and other repeated patterns. Of course, that detail is missing in the product descriptions, with the exception that some ads might say "up to 320 GB compressed". Your mileage may vary...

So to determine if your data can be compressed, you'll need to run compress on each file to determine approximately what the compressed size will be. Then expand the file back again and add the result to your total. The total for all files will roughly indicate how much tape will be needed.

In other words, you are getting the result that the tape drive can produce -- your files are not very compressible (typical for binary files) so you will only get 150-160 GB maximum.

See http://en.wikipedia.org/wiki/Digital_Data_Storage

[Mike Miller_8]

When the tape's full it doesn't really matter what your compression ratio is - the tape is full. Most archive software already have logic in them to compress the data as it's written to tape so trying to compress the files within windows will likely not help.

Your best bet is to see if there are any temp files (or other files)that can be deleted (or just mount a second tape).

I agree with Bill, the tapes should list their native storage capacity when they market them.