I am running NetBackup Ent 6.5 (Windows). Our tape library is an HP MSL6000 with dual LTO 3 drives.
We are using all LTO 3 media. I am curious why some media is "full" with seemingly low data volume and other media is "full" with much higher volume.
For example when I run the available_media command and evaluate my media that is listed as Full:
Some media has 366 GB and is full and some media has over 1 TB and is full. I know that LTO 3 has capacity of 400/800.
I am just curious why media fills with vastly different amounts of data (according to NetBackup).
Big difference is when you place DB in a tape and normal files, you can always use a special pool just for DB backups and change your policies to that DB_Pool, this way you dont mix them and that gives you a better usage of the media.
Some media have "bad spot" where data are not written. Also Interblock gab take up space. So you my end up with less capacity than estimated. As a rule of thumb estimate 400G per tape. Everything above is a discount ;)
From : http://www.computerhope.com/jargon/i/intergap.htm
Also known as an Interblock gap and abbreviated as IBG or IRG, an Interrecord gap is a break between data records on hard drive and magnetic tape that serves as a safety margin for data overwrites. Interrecord gaps are also used as a marker for the end of data.