cancel
Showing results for 
Search instead for 
Did you mean: 

Lto6 tape capacity is reduced, after data is backed up

trungqui2518
Level 2

Dear company ,

I am using Veritas Backup Exec 16 software, Hp LTO6 Ultrium 6250 tape drive, HP LTO6 tape.

The total amount of data I need to backup is 988 GB. But after the backup is complete, the display value on the tape is 825GB (lose about 150GB).
I have tried to restore some backups randomly, the files are still normal.
I have had this problem several times.
( My backup data is media ) 

Does the problem affect my data?
Please give me advice on the above case.

Regrads,

Trung Nguyen

6 REPLIES 6

Gurvinder
Moderator
Moderator
Employee Accredited Certified
Can you check the tape stats. What’s the compression ratio it shows ?

Dear Gurvinder,

Sorry, for a late reply to you.

In Media properties, Compression ratio: 1.18: 1

Does the ratio affect?
In order to value the actual data capacity equal to the capacity value on tape after backed up, I will adjust that compression ratio ?
You give me advice.

Regrads,

Trung Nguyen

P/s: Please see the attached files for more details.

 

Gurvinder
Moderator
Moderator
Employee Accredited Certified
The compression ratio is governed by the kind of data you backup. It cannot be set. In your case, the compression ratio is 1.18 : 1

If you check the tape statistics, it shows data written on tape is 998 GB and this data when written after compression is 839 GB on tape(since data was compressed and written). 839 GB multiplied by 1.18 should be roughly the data written value.

Dear Gurvinder,

Thank you, I understood the problem.
But let me ask a problem related to the compression ratio above:
Can I check the compression ratio of files (video, audio ..) before backup to the LTO tape?
Or to backup to tape, the new compression ratio value is available.
From there I can calculate how much storage.

Thanks for your supports,

Regrads,

Trung Nguyen

Gurvinder
Moderator
Moderator
Employee Accredited Certified

there is no fixed compression that you get. What if your data size increase and compression remains or not remain same depending on data type etc. Once you start using the tapes, maybe you can look at how many tapes get used in a week if you are appending all your backups. Then for that amount of total data , you can keep that many tapes. As and when data increase you may have to increase the number of tapes.

Dear Gurvinder,

I clear problem .

Thanks for your support.

Regards,

Trung Nguyen