Posts Tagged ‘DRS’

High Availabilty. Why Hyper-V delivers better

May 29, 2012 Leave a comment

That’s kind of interesting subject to talk about

Taking as a sample 3 cluster node, where every node has  1(one) connection to a shared storage.

By using VmWare,  if one of the VmWare hosts ever lose the IP storage connectivity ( an fault on the ISCSI nic for example ), your Virtual Machines are on the dark, you will probably receive an Blue Screen. The VmWare monitoring will try to start (vmotion) the Virtual machine on the same host or on any other host that has storage connectivity.

Now, the clever solution from the Hyper-V
if the one of the Hyper-V hosts lose IP storage connectivity ( an fault on the ISCSI nic for example ), the Hyper-V will redirect the Storage traffic to the CSV and the VM  still working : no blue screen, no restart.

In a Hyper-V Failover Cluster with CSV, all storage I/O is Direct I/O meaning each node hosting a virtual machine(s) is writing directly (via Fibre Channel, iSCSI, or SAS connectivity) to the CSV volume.  But in case of lost of Storage connectivity in one of the hosts the traffic will be redirected over the CSV network to another node Host in the cluster which still has direct access to the storage supporting the CSV volume.  This functionality prevents the loss of all connectivity to storage.  Instead, all storage related I/O is redirected over the CSV network. This is very powerful technology as it prevents a total loss of connectivity thereby allowing virtual machine workloads to continue functioning.

Of course there are other fault scenarios to consider and yes, I know that the recommedation is to have redundant storage connection, but that’s kind of expensive solution and does not take the fact that the Hyper-V solution is more clever.

If you ever experienced this situation I would like to hear your input.