This is something that has kept me busy for a while. For the past 2 years there were some challenges with regards to the use of MCS and XenDesktop/XenApp in combination with vSAN. In fact, Citrix never supported vSAN and MCS, and it actually did not work either. PVS worked great in combination with vSAN however. Some customers though prefer to use MCS. After various discussions, emails and engineering discussions it seems that the problem customers faced has finally been resolved.
Citrix recently announced a hotfix that will allow you to use MCS with XenDesktop/XenApp 7.12 and vSAN version 6.0, 6.2 or 6.5. You can find the hotfix and details here: https://support.citrix.com/article/CTX219670
I would like to thank a couple of folks for making this happen, from Citrix: Christian Reilly (Thanks for connecting me to everyone!), Vishal Ganeriwala, Paul Browne, Yuhua Lu, Rick Dehlinger, Amanda Austin and from VMware Weiguo He, Tony Kuo and Sophie Ting Yin. Thanks everyone for making this happen in between releases. I am certain our joint customers will appreciate this! Note, that it is not a full statement of support (yet), but a great step in the right direction!
For those interested in XenDesktop/XenApp with vSAN, make sure to read this great reference paper by Sophie Yin. It provides a lot of detail around performance etc.