Newbie question - HP Dat72

[573910707]

Hi there,

It's my first time on the forum, so I apologise if I'm asking a question that's already been answered. I've had a good search but haven't been able to find the answer anywhere.

I have a HP StorageWorks DAT72 drive (32GB native capacity, 72GB compressed) connected to my windows 2000 server. Each night a backup runs, and the size of the backup is around the 48GB mark. Recently the backups have been ejecting the tapes when it gets near to completion, and requests another tape to finish the job.

On the backup job selections I have selected "Use hardware compression or use software if unavailable". I know that the drive has compression, and that the tapes can therefore hold a lot more than 48GB of data.

Could anyone think where I may be going wrong?

Many thanks
Ian

[Ken_Putnam]

2:1 compression is a marketing thing, not an engineering thing (see http://seer.support.veritas.com/docs/199542.htm )

If you are getting 48GB on a 32GB (native) tape, you are getting about 1.5:1 compression. I geneally figure on about 1.3:1, so you are ahead of the game at this point

[Ajit_Kulkarni]

Hello,

The answer given to you querry by the Forum participant is correct. The technote given gives the detailed explanation it. However to add to it,Compression can be done through hardware (if your hardware supports it) or through software. Hardware compression is the feature of the drive you are using rather than Backup Exec software whereas, software data compression compresses the data using the software before it is sent to the storage device.
Twice the native capacity of a media is usually given as the maximum possible amount of data that could be written to a tape. It should be noted that this figure is rarely, if ever, achieved. This is due to the varied types of data that are found in most environments(text files, graphic files, already compressed files).

Hope it clarifies the issue. Do revert for any further querries.

NOTE : If we do not receive your intimation within two business days, this post would be "assumed answered" and archived.

Regards.

[573910707]

Hi there

Your kind assistance answered my query perfectly.

Many thanks for your kind help.