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Back Up Compression

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Martin_259
Occasional Visitor

Back Up Compression

Hello,

Please help:

I am trying to back up ca 50 GB of data (Lotus Notes databases) on to 40/80 GB DLT tape drive (Storage Works not VS 80)

However I am ubale to do so as the tapes fill up and compression doesn't appear to be working although the option is set on the tape drive and the option to use software compresion is selected as well.

(Back up software is ArcServe 2000)

Thanks
6 REPLIES
Mahesh Kumar Malik
Honored Contributor

Re: Back Up Compression

Hi Martin

See if Windows native backup utility gives you an option to compress and thus test the backup. If it works, then ArcServe2000 has functionality problem.

Regards
Mahesh
Wim Van den Wyngaert
Honored Contributor

Re: Back Up Compression

Your tape may be initialized with the wrong density. Use a blank tape or do whatever to initialize it again.

Wim
Wim
Patrick Wallek
Honored Contributor

Re: Back Up Compression

It is ALWAYS best to assume the LOWEST amount of data for a tape. I *NEVER* count on getting more than the native capacity (no compression) of the tape. A DLT8000 is a 40GB native and 80GB *IF* you get a 2 to 1 compression ratio.

It is entirely possible that it is attempting to compress the data, but if the database is very full, you may not be getting much compression. What you require may not be possible without spanning 2 tapes.
generic_1
Respected Contributor

Re: Back Up Compression

I would just make sure you have enough tapes and that your tape utility supports tape spanning. Also make sure you have the correct tape type. Some tape mediums come in different lengths.
Antoniov.
Honored Contributor

Re: Back Up Compression

Hi,
compression can guarantee 2:1 ratio; may be smaller and sometime may be equal to 1 that means tape doesn't compress any data.
If your database use some compression technique you MUST use 80Gb tape.

Antonio Vigliotti
Antonio Maria Vigliotti
Marino Meloni_1
Honored Contributor
Solution

Re: Back Up Compression

have a check at the following links:

density setting: http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=lpg50551

Be sure to disable SW compression and use only HW : http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=lpg50030

Check also for performance problem that can slower the capacity of a tape : http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=lpg50167

The default capacity (native capacity) is 40 GB, in optimum conditions, and the source data allow compression in a ratio of 2:1, you can get 80 GB. Nowadays, the data comming from the servers are ususaly already optimized, and the compression allowed is very poor. This is the first factor that could reduce the capacity on a tape.
Also other factor can influence the capacity, if the tape is damaged, several blocs will be not available to be written, then total capacity will be reduced.
Another factor is if the drive itself have problem on some channel of the read/write head, this will reduce the capacity because some of these channels will not write data.
One more factor is if the drive cannot write data in a "streaming mode", this means that the data are not arriving from the server at a troughputh high enough to feed the tape, and then, some parts of the tape will stay blank, reducing his capacity.

You can use LTT to identify the cause of this reduced capacity on your drive

marino