So I have seen estimates here and there stating that upwards of 80% of VI installations are SAN attached. For me personally, the number is more towards 95% but I still do have some clients that choose, due to fiscal restraints, to forgo the SAN. From my perspective, ESX without shared storage is like Tivo without the remote. Its just not quite the same experience.
But for those 5% - 20% Storage Challenged customers out there, while saving for a SAN, operations must continue forward. One aspect that has come up recently with my clients is replication of Virtual Machines. With a traditional SAN, there are plenty of options, however with DAS, the options are limited. Vizioncore and Veeam both make the job of replication a little easier to tackle.
Vizioncore distributes vReplicator and Veeam distributes Veeam Backup.
While vReplicator's sole purpose is replication, Veeam's offering is primarily backup and restoration. Veeam adds in replication to Backup 2.0 as a feature. In my opinion, both products do a great job replicating VMs from one site to the next. They both will replicate from DAS to SAN, SAN to SAN, SAN to DAS and DAS to DAS. They are both VirtualCenter aware which means once you set the jobs up, they will track all migrations of the VMs through VirtualCenter and continue to replicate from the new ESX host.
Both have differential engines to make sure you are not sending GOBs of traffic across the wire during replication events. Just the deltas.