I’ve posted about vSphere HA advanced settings various times in the past, and let me start by saying that you shouldn’t play around with them unless you have a requirement to do so. But if you do, there is a KB article which I can highly recommend as it lists all the known and lesser known advanced settings. I had the KB article updated with vSphere 5.5 advanced settings yesterday (Thanks KB team for being so responsive!) but it also applies to vSphere 5.0 and 5.1. Recommended read for those who want to get in to the nitty gritty details of vSphere HA.
I had a question last week around HA’s datastore heartbeating, the question was if datastore heartbeating still worked if you only have 1 datastore in your environment. I can understand where the question comes from as HA throws this error that you need to have 2 datastores at a minimum for HA datastore heartbeating to function correctly. I want to point out that even though HA says that 2 datastores is the minimum, even when only one datastore is available it will be used for heartbeat purposes. Yes this error will be there on your cluster, and yes you can suppress it using “das.ignoreInsufficientHbDatastore“. I figured others might be hitting the same error and have the same question so why not document it?!
I have been digging for a long time now to figure out what the minimum bandwidth requirements are per concurrent vMotion. After a long time I finally managed to get a statement. In the past the statement was made that 622Mbps was the minimum required bandwidth for vMotion, it appears that this is incorrect for vSphere 5.0 and higher. With vSphere 5.0 a new feature called Stun During Page Send (SDPS) was introduced and this has decreased the bandwidth requirements from 622Mpbs down to 250Mbps per concurrent vMotion.
Always nice to know right?!