We have SLP used in backup which has duplication to tape operation once backup completed. Problem is duplication to tape is running very slow causing SLP backlog to increase. I have increase the buffer setting on media servers but no much improvement in duplication to tape. Yes backup to tape is running with good speed 50-70 mbps but not getting good performance in duplication.
Below is the environmental details.
Media/Master server : Netbackup 7.7.3 all are suse linux
We are using Datadomain for backup destination then SLP to perform duplication to tape.
IBM tape library which has 21 LTO 4 tape drives and all is running fine and used in duplication. I have calculated total size written to tape is 15TB per day which is not enough to handle backlog while backup to disk is approx 100 TB per day
Please suggest if anything can be done.
How many media servers do you have?
And what is the network speed between DD and media servers?
Dedicated network between media servers and DD?
How many simultaneous duplications? And what is the spread between the media servers?
(I guess DD is not SAN attached to media servers, right?)
Have you considered the data path during duplication?
i.e. DD -> rehydrate -> network -> Media server -> tape drive.
Compare this with backup :
Client -> network -> Media server -> tape drive.
Have you enabled bptm and bpdm logs (level 3) on media servers to evaluate results of buffer sizes before and after making changes?
80MB/sec per stream is what you can expect from a data domain running DDOS 5.x (first hand experience). I do not have information if this has been improved in DDOS 6.x
The re-hydration speed in a Data Domain is depending on the age of data. Newer data re-hydrate faster than older data, this is due to internal block optimization with-in the Data Domain.
So - if you know data has to be stored on tape for a extended time - consider to duplicate data to tape in the beginning of the SLP instead of when data is about to expire (the active/postponed option in the SLP configuration).
In the SLP configuration there is a section called "State of secondary operation processing" - you can either select to process the duplication at birth of backup (The "active" option) or at the end of a copy (backup) life time (postponed option).
Active is the default - and is likley what you have configured - in this case you can't do anything. However if SLP is configured with the Postponed option , you should consider to switch to "active" when the backlog issues is resolved.
Hope this explain