Windows Server 2003

NBU Duplication Multiplexing

Jim Turner

NBU Duplication Multiplexing

With Data Protector, an object copy allows you to multiplex numerous source streams down to a small number of target drives.  For example, you could read from 30 VTL drives and multiplex those 30 streams down to 4 physical drives in an EML tape library.


It would appear looking at NBU 7.5 that multiplexing in this manner is not possible.  If you only have 4 target physical drives, NBU only allows you to use 4 virtual drives in the VTL to read source images.  If you have 30-40 source images to duplicate, this limitation creates an unnecessary performance bottleneck.


From NBU's duplication help:


Number of Read Drives - The number of drives to use for reading backup images.  When you enter a number of read drives, the same number is entered into the Destination Write Drives field.  You must have an equivalent number of read and write drives available.


Write Drives - The number of write drives.  This value is the same as the number of read drives.


So is there no way at all to read 30 source images from a VTL with 30 drives and multiplex those down to only 4 target physical tape drives?  The 1:1 read:write limitation badly constrains duplication performance.