I received a question a while back about the bandwidth requirements for long distance vMotion, aka live migration across distance. I was digging through some of the KBs around stretched clusters and must say they weren’t really clear, or at least not consistently clear…
Thanks everyone. Is Long Distance vMotion still requiring a minimum of 622 (1Gb) in current versions? /cc @duncanyb
— Kurt Bales (@networkjanitor) October 3, 2012
I contacted support and asked them for a statement but have had no clear response yet. The following statements is what I have been able to validate when it comes to “long distance vmotion”. So this is no VMware support statement, but my observations:
- Maximum latency of 5 milliseconds (ms) RTT (round trip time) between hosts participating in vMotion, or 10ms RTT between hosts participating with Enterprise Plus (Metro vMotion feature).
- <update>As of 2013 the official required bandwidth is 250Mbps per concurrent vMotion</update>
- Source and destination vSphere hosts must have a network interface on the same IP subnet and broadcast domain.
There are no longer any direct bandwidth requirements as far as I have been able to validate. The only requirement VMware seems to have are the ones mentioned above around maximum tolerated latency and layer 2 adjacency. If this statement changes I will update this blog post accordingly.
PS: There are various KBs that mention 622Mbps, but there are also various that don’t list it. I have requested our KB team to clear this up.