You can use a single set of paired Site Recovery Manager sites to protect virtual machines in both directions. Each site can simultaneously be a protected site and a recovery site, but for a different set of virtual machines.
You can implement bidirectional protection by using either array-based replication or vSphere Replication. If you are using array-based replication, each of the array’s LUNs replicates in only one direction. Two LUNs in paired arrays can replicate in different directions from each other.
For information about the numbers of virtual machines for which you can establish bidirectional protection between two sites, see http://kb.vmware.com/kb/2034768.