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Backup job started to fail due to backup size

Created: 17 Dec 2012 | 4 comments

Dear All,
I am using backup exec 2010 for the Backup Jobs with HP Ultrium-3 drive drive.
I am using Media C7973A 800 GB RW Ultrium-3  LTO

all of sudden the backup job started to fail due to backup size, I checked on the media properties, statistics and found that the total capacity is 391 GB !!!

Media type is set to LTO , I  changed it to LTO 4 (800 GB) but with no effect.

I used HP Storage works library and tape tools and the capacity is seen as 800 GB.

Kindly advice why the media is seen as 391 GB only in Backup Exec ??

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Kiran Bandi's picture

LTO 3/Ultrium 3 medias can hold data of size 400 GB in native mode and 800 GB of data in compressed mode.

It looks like there is no compression being achived on the data that is being backedup. Have you enabled compression in backup job? Also note that the compression ratio that can be achieved a lot depends on the type of data that is being backedup.

To my knowledge, changing media type in software doesn't have any effect on the amount of data that can be stored on a tape.

pkh's picture

A LTO3 tape can only hold 400GB of uncompressed data and changing the media type will not change this capacity.  The reason why it is listed as 391GB is because of overheads, just like when your format a 1TB disk and get 800-900GB of free space.

The 800GB is a marketing thing which assumes a 2:1 compression ratio.  This ratio is hardly achievable in real life.

Take a look at your tape statistics and see how much of actual data is stored on the disk. See my article below on how to interpret the tape statistics.

If you have verified that compression is enabled in your job (check your joblog) and you are getting less data on your tape than the native capacity.  There are a couple of possibly.

1) You have a bad tape which needs to be changed.

2) Your tape drive is faulty

3) You are compressing data which is already compressed, like zipped files, movie and sound clips.  See my article below for an explanation.

Nermeen's picture

I checked on the media and found that ths Compression ratio is 2.3.1

On the Device itslef "Enable Compression" is ticked

I can not find the compression settings in the Backup job itself.

I am facing this issue with many tapes and i didnt find any failures related to the device itself

pkh's picture

Check your joblog and there will be a line saying whether compression is on or off.

If the compression ratio is 2.3:1, then compression is working.  It could be just that your data is too much for 1 tape and a second tape is required.