Forum Discussion

joe1871's avatar
joe1871
Level 3
10 years ago

Tape Duplication - Is Compression Enabled By Default

I had a backup job that actually spanned three tapes - it has at least 3 TB or more data that it is running a full NDMP backup on.  This is from a NetApp filer, via NDMP, and to Ultrium 5 tapes.  The...
7.5
Backup and Recovery
Managing Backup Devices
NetBackup
Reporting
Windows Server (2003-2008)
  • mph999's avatar
    mph999
    10 years ago

    The drives use hardware compression by default, for example, if on Solaris the path was /dev/rmt/0cbn to the drive, the 'c' bit of 'cbn' means compress.

    So the tape driver / tape drive hardware handles compression.

    I would run a verify on each copy, make sure they check out.

    At the moment, I can't explain the difference, but have seen similar on a multiple in-line copy where one copy used x tapes and the other used x+1 tapes, exactly the same data being sent to each drive at 'almost' exactly the same time.

    Both copies were readable, issue was a fault with the tape drive, one of them wasn't compressing.

     

jim_dalton's avatar
jim_dalton
Level 6
10 years ago

I dont see theres any issue if what you say is true Joe: if you know for a fact that the original backup was not compressed and the duplciate was then its entirely believable. Personally I'd be adressing why the original wasnt compressed as it is unusual. The time to duplicate is no concern: its tape to tape not filer to tape, and the bottleneck in NDMP backups is almost always NDMP unless you are dealing with large files. What speed did the original 3 -tape job run at? Jim