Forum Discussion

thomas_crowe's avatar
thomas_crowe
Level 2
13 years ago

Question about MSDP and Automated Image Replication (AIR)

I am working with Netbackup 7.1 and researching AIR with MSDP.  I have come across the statement "If you are using MSDP for A.I.R, only the deduplicated data gets replicated. If the target already ha...
7.1.x and Earlier
Backing Up
Backup and Recovery
Deduplication Option
Features
NetBackup
Windows
  • RiaanBadenhorst's avatar
    RiaanBadenhorst
    13 years ago

    Hi,

     

    Its just doing optimized duplication as you would within a NetBackup domain when using SLP's to duplicate from one MSDP to another MSDP (or PureDisk to PureDisk). Remember these are storage devices that work at a layer "below" netbackup. The storage devices talk to each other to find out, what's new, what's already stored, and what to send.

     

    You don't configure any load balancers. The setup should reflect a regular push configuration where only the local media server is listed/configured in each storage unit respectively.

The_real_Alex_D's avatar
The_real_Alex_D
Level 4
13 years ago

The communication takes place at the storage server level.  In the case of MSDP the media server IS the storage server but for PDDO, OST and 50xx appliances the storage server is separate from the media server. 

The behavior is the same for both inter-domain (optimized duplication) and intra-domain (auto image replication) communication.  (It's also very similar to client side deduplication during the initial backup.)  It all comes down to the signature associated with the data segment.  Each segment has a unique signature(kind of like the check sum if you like) that is stored on each storage device along with the segment.  (Exactly how the segment and signature are stored depends on the device.)

During a duplication the source storage server sends each segment signature to the target storage server.  The target storage server checks to see if it already has that segment.  If it doesn't it asks the source storage server to send over the segment. 

That's pretty much all there is to it.  No need for any fancy load balancing and the good thing is that because each signature is unique even where you have multiple sources duplicating to the same target you will never have to send the same segment twice.