During one of our many discussions at VMworld 2017, I was asked about supporting Fault Tolerance on vSAN Stretched Clusters, more specifically SMP-FT. Now to be clear, we can support SMP-FT on vSAN since version 6.1. The difficulty with supporting SMP-FT on vSAN stretched cluster has always been the possible latency between the data sites, which could be up to as much as 5ms. This is far too high to support SMP-FT on a VM that has data replicating between data sites, and for that reason, we stated categorically that we could not support SMP-FT on VMs deployed on vSAN…
Many of you who are well versed in vSAN will realize that we released a Secondary Failures To Tolerate (SFTT) feature with vSAN 6.6. This meant that not only could we tolerate failures across sites, but that we could also add another layer of redundancy to each copy of the data maintained at each of the data sites. Of course the cross site replication (now referred to as PFTT or Primary Failures To Tolerate) is still based on RAID-1 mirroring and this continues to require a third site for the witness appliance, so that quorum can be obtained in the…
The last of my VMworld 2017 sessions is now available for viewing. This is the vSAN Networking session, which I co-presented with Andreas Scherr. Andreas is responsible for taking care of all of our vSAN proof-of-concept deployments in EMEA. In this session we cover many aspects of vSAN networking design and configuration, such as NIC teaming, load balancing, supported topologies, and so on. The session includes some very interesting demos, highlighting what can go wrong when the networking is not optimal. Hope you like it, and feedback is always welcome.
After publishing the vSAN Networking Guide earlier this year, Paudie O’Riordain and I received numerous questions regarding support on having different stretched clusters hosting each other’s witness appliances. These queries arose because we discussed a 2-node (ROBO) topology which allowed this to sort of configuration (i.e. the cross hosting of witnesses) via special request. But in the networking guide, we explicitly stated that this was not supported with vSAN stretched clusters. However, after some further testing by our engineering teams, we can now relax this restriction if there are 4 independent sites hosting the different stretched clusters. In this case,…
Now that the US VMworld 2017 event in Las Vegas is over for another year, the focus turns to the VMworld 2017 event in Europe. This year, it once again takes place in Barcelona, Spain. A difference this year is that there is not much of a gap between US and European events, with the Europe event taking place in September this year rather than in October like it usually does. Just like the VMworld Las Vegas event, I am co-presenting on three sessions. In additional to that, in Barcelona, I am also hosting a number of Meet-The-Expert round-tables on…
A quick note to let you know that the session that I delivered on day 1 of VMworld 2017 is now available on YouTube. The session is entitled “A Deep Dive into vSphere 6.5 Core Storage Features and Functionality” and I delivered this with Cody Hosterman of Pure Storage. Judging by the feedback, and the number of passing comments I received in the hallways at VMworld over the past 2 days, it seems that this session was very well received indeed. Hope you like it.
Does anyone remember the ATS Miscompare issue? This blog post from 2 years ago might jog your memory. It is basically an issue that arose when we began using ATS, the VAAI Atomic Test and Set primitive, for maintaining the ‘liveness’ of a heartbeat in vSphere 5.5U2. After making this change, a number of customers started to see “ATS Miscompare detected between test and set HB images” messages after upgrading to vSphere 5.5U2 or later. The HB reference in the message is shorthand for heartbeat. In previous releases, we did not use ATS for maintaining the ‘liveness’ of a heartbeat.…