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HP 36/72 GB DAT DRV compression...

Calvin_30
Occasional Visitor

HP 36/72 GB DAT DRV compression...

I am a novice here, please help me with this question, thanks a lot.
How can a hp DAT 72 tape achieve its compressed capacity (i.e.
72 GB)? As I tried with BrightStor ARCserve Backup, it only can store up to
36 GB capacity even if I selected "Compress backup data on the tape" or "Compress Files Before Backup".
What should I do?
Thank you.
2 REPLIES
Stuart Whitby
Trusted Contributor

Re: HP 36/72 GB DAT DRV compression...

This figure is not guaranteed. I'm not sure how ArcServe reports this, but if you do software compression and can successfully get a 2:1 compression ratio, then you have already written 72GB onto this drive, even though only 36GB of compressed data has been written. If hardware compression is enabled, it should show the correct figure. If this data is in an already highly compressed format (such as JPG or MPG files) then you will be unlikely to achieve anywhere close to a 2:1 compression ratio. If you are writing text files, then you are likely to achieve very high compression - quite possibly getting 3 or 4 to 1 on this drive.
A sysadmin should never cross his fingers in the hope commands will work. Makes for a lot of mistakes while typing.
Calvin_30
Occasional Visitor

Re: HP 36/72 GB DAT DRV compression...

Thank you for your reply, however, I still got problems...

>> If you do software compression and can successfully get a 2:1 compression ratio, then you have already written 72GB onto this drive, even though only 36GB of compressed data has been written.

1) How can I check the compression ratio and whether those data are compressed or not?

>> If hardware compression is enabled, it should show the correct figure. If this data is in an already highly compressed format (such as JPG or MPG files) then you will be unlikely to achieve anywhere close to a 2:1 compression ratio.

2) How can I enable hardware compression?
3) How can the figure be shown?
4) How about Norton Ghost (.gho) files?

Sorry for many silly question, but I really need help. Thanks. ._.