SMP-FT support on Virtual SAN
There have been a number of questions recently about SMP-FT on Virtual SAN. The Symmetric Multi-Processing Fault Tolerance (SMP-FT) is a feature that many VMware customers have been waiting for. With the release of vSphere 6.0, the SMP-FT capability finally became available. This release did not include SMP-FT support when the VM was run on VSAN however. With the release of vSphere 6.0U1, which included VSAN 6.1, there is now support for SMP-FT when the VM is run on VSAN.
There are some caveats when it comes to the different VSAN deployment methodologies:
- On standard VSAN deployments, SMP-FT is supported
- On ROBO/2-node VSAN deployments, SMP-FT is supported (announced at VMworld 2015 in Barcelona)
- On stretched cluster VSAN deployments, SMP-FT is not supported. The latency distances (up to 5 msec RTT) are simply too great for fault tolerance
Another common question is whether the remote witness appliance for both stretched cluster and 2-node/ROBO deployments can be protected by SMP-FT on a remote host and remote datastores. While this could work in theory, it has not been tested. The general consensus is that vSphere HA should be enough to protect the witness appliance.
With this in mind, lets see how one would go about configuring SMP-FT on a standard VSAN deployment.
This is quite straight forward. FT is displayed as an option from the VM drop down action menu in vSphere 6.0u1 for VMs residing on VSAN. If any anomalies are detected, these are reported in a pop-up window. Here is an example taken from my lab setup:
A number of issues are reported in this case. First, one of the nodes in the VSAN cluster does not have Fault Tolerance Logging enabled on any of its VMkernel ports. Secondly, the VM is using devices that will prevent FT. The first is that it has 3D enabled on its video card, and second it has a CDROM device attached. Fix all of these issues before enabling FT once again.
Now when FT is turned on, you are prompted for a datastore to place the secondary VM.
Since this is the VSAN datastore, and we can tolerate failures, we can place the secondary VM on the same VSAN datastore. In the storage field, select “Browse…” and choose the vsanDatastore:
The next step is to select one of the hosts on which to run the secondary VM. Once that is completed, FT is ready to go. This will create an FT view in the VM Summary page, as follows:
In my environment, I enabled FT on a VM that was powered off. I then powered on the VM to look at the various stages that it goes through. You can see the FT status change to starting:
And then change to protected:The VM is now FT protected on VSAN. However, only one view of the VM is available on the hosts and clusters view. To look at the VM in more details, select the host, and then related objects, followed by virtual machines. Here is the primary VM view:
And here is the secondary VM view: