Compression and Capacity

[A_van_der_Boom]

I have read some questions about tape capacity and compression ratios and checked mine and although I am not unhappy with them I do have some questions.

I am using Ultrium LTO2 tapes 200GB uncompressed / 400GB compressed and backup a variety of data, documents, pictures, movies, databases etc.. When I check the media properties of a tape I see a total capacity of 17.9GB (which is also the used capacity) while the tapes are 200GB, the total amount of bytes writen varies from 260-290GB (depending on the amount of data) The backup itself is divided over 2 tapes and the compression ratio is 16.5:1
When I select the 'Media Type' I see several types of LTO settings, ranging from LTO,LTO-CLN, LTO to LTO (and some others with lower capacity then 200GB)

My questions are
- Why does the avaiable and used capacity only show 17.8GB instead of 200GB ?
- The compresson shows 16.5:1 while most of the time I see comments on that 2:1 ration is a marketing thing, so what is 16.5:1 a miracle or just a mismatch meaning it should say 1.65:1 ?
- The media type is now set on LTO but what does the LTO means, would it help to change this setting. (if one would now what those settings mean) ?

(BE9.1SP2 on W2k3)

Regards
A van der Boom

[Sharvari_Deshmu]

Hello,

I
To resolve the incorrect media capacity issue we request you to perform the following steps:

1 Please check whether the device is "tested" in the compatibility list.If yes then please install latest Vertias drivers.

Harware compatibility list for stand alone:
http://support.veritas.com/docs/271382

Harware compatibility list for auto loaders:

http://support.veritas.com/docs/271383

VERITAS Backup Exec (tm) 9.1 - Device Driver Installer (20050115) - Includes Tape Driver Release (20041231) and Robotic Library Release (45) (Intel Only) http://seer.support.veritas.com/docs/273853.htm

If not tested then please install latest manufacturers and then verify the result.

2. Also please check the device configuration with the help of the technote below:

How to troubleshoot issues with a Robotic Library or Tape Drive in Backup Exec 9.x and 10.0

http://support.veritas.com/docs/255501

3. Please upgrade the firmware also.


II

Regarding compression we would like to inform you that
when using compression it is important to remember that the 2:1 compression ratio frequently assumed or stated in technical documentation is an ideal seldom reached as a practical average.
Some files compress better than others. Text files are probably the most compressible files in general while high-density graphics files like files with .jpg, .gif, .zip, or .cab extensions are not likely to compress at all. Also, many programs, including some database and mail programs, already compress the files they control. Further, Backup Exec offers the choice of either hardware or software compression. When the hardware compression is used, the compression is done by the backup device not by the Backup Exec software. In some cases software compression may be an alternative if poor results are achieved with the use of hardware compression.

Refer to the following TechNote for more information:

http://seer.support.veritas.com/docs/199542.htm


Thanks,

NOTE : If we do not receive your reply within two business days, this post would be marked ‘assumed answered’ and would be moved to ‘answered questions’ pool.

[Sheetal_Risbood]

As per our previous reply, marking the case as assumed answered and moving it to answered questions pool.