Oracle backups to Data Domain

[rowl]

I am investigating some compression ratios on Data Domain and see some wide ranges in the reported data reduction. In looking over the Data Domain best practices guide for Oracle I see a reference to setting FILESPERSET to 1 in rman. I understand what this does, but does this have a substantial impact on compression? I would like to investigate this further, but to get some cooperation from our DBAs I will need to be able to make some statement of benefit for looking into this.

Thanks,
-Rowl

Note: When I state compression I am saying this in Data Domain terms where this includes both deduplication and lz compression.

 

[GregE]

DataDomain deduplicates, then compresses that deduplicated data. That being said, logic would have it that it wouldn't make any difference how many files per set.

I say that from research and talking with DD techs when I was giving DD a hard look, but I don't have DD in my environment.

 

[johansen]

we have the same "issue" that our tsm server which stores oracle and sql backups has the lowest compression ratio compared to all others (ndmp,exchange,aix, etc). the recommendation from EMC is definitely to set filesperset to "1". but we have this since we implemented the DD and we cannot see any increase in the compression ratio.

 

[rowl]

There is a good document on best practices for Oracle backups to DD. Filesperset=1 and no rman compression are the big ones from what I have seen. Getting the DBAs to make the filesperset=1 and double check no compression in rman raised our compression from 2.4:1 up to 4.9:1 overall and they only changed a small number of backups over. If I use the filesys show compression <file> I see some files reporting well over 20:1 compression. It will take weeks to get our entire environment switched over but so far this looks promising.