One-to-Many and Multihop Volume Sets

The Sun SNDR software enables you to create one-to-many and multihop volume sets.

In a one-to-many volume set, you can replicate data from one primary volume to many secondary volumes residing on one or more hosts. One primary and each secondary host volume is a single volume set (each secondary volume requires its own unique secondary bitmap volume). When you perform a forward resynchronization, you can synchronize one volume set or all volume sets; in this case, issue a separate command for each set. You can also update the primary volume by using a specific secondary volume. FIGURE 1 shows one primary and three secondary host volumes and therefore three volume sets: A and B1, A and B2, and A and B3.

Note – You can group one-to-many sets that share a common primary volume in a single I/O group to operate on all sets simultaneously instead of issuing a separate command for each set. See also “Order-Dependent Writes and Volume Set Grouping” on page 13.

In a multihop set, the secondary host volume of one volume set can be the primary host volume of another volume set. FIGURE 1 shows one primary and one secondary host volume; the secondary host volume B becomes the primary host volume A1 to the secondary host volume B1.

	One-To-Many		Secondary host volume		B1
			/dev/rdsk/c0t0d0s5		B1


A Primary host volume			Secondary host volume		B2
A Primary host volume					B2
/dev/rdsk/c0t0d0s5			/dev/rdsk/c0t0d0s7
			Secondary host volume		B3
			/dev/rdsk/c0t0d0s9

	Multihop

Primary host volume		Secondary host volume		Secondary host volume

/dev/rdsk/c0t0d0s5 /dev/rdsk/c0t0d0s5 /dev/rdsk/c0t0d0s5

One volume set

Another volume set

A = Primary host volume

B = Secondary host volume

FIGURE 1 One-to-Many and Multihop Volume Sets

18 Sun StorEdge Network Data Replicator 3.0 Configuration Guide • June 2001