VSAN and Disconnecting Hosts: Be Careful How You Remove Host Resources!
There are a lot of people testing the waters with VMware VSAN, and one of the challenges with bringing a new technology on board is understanding the management processes to keep it running. Shared-nothing clustered storage is probably one of the more challenging environments to maintain just because of the nature of how sensitive it may be to change.
The Somewhat Unwritten Guides for VSAN
VMware VSAN is still relatively new, and with more production instances popping up around the world, customers are asking some interesting questions. One such question that came up in the VMTN Communities page was around whether disconnecting an ESXi node from VSAN would affect the overall capacity.
The short answer is “yes”. But the question comes around what exactly is being disconnected? In the case of this question, the real answer is that the customer should not “disconnect” which detaches the host from vCenter altogether, but the system should leave the VSAN cluster during maintenance.
By actively and safely leaving the VSAN cluster, it not longer participates as a VSAN node and it will safely remove from the active cluster. This could be chalked up to semantics, but with clustered storage, those semantics can lead to unfortunate results if we go the wrong way.
As more of the use-cases arise for VMware VSAN, we will see more great documentation of processes and operational best practices. One lesson that we can learn with any such system is to make sure that we are asking the right question 🙂
Also, here is quick video that shows just how easy it is to add VSAN to your VMware environment: