mixing ESXi 5.1/5.5 and ESXi 6 in one HA/DRS-cluster

Hello Community,

I´m sorry if this question is answered in another thread, but i used google and the community search and haven´t found an answer.

Are there any known issues when mixing ESXi 5.5 and ESXi 6 hosts in one DRS/HA-cluster?

I know that we have to have a look at the virtual machines hardware versions (hardware version 10/11) and the VMware tools version (6) due to compatibility, but are there any other potential problems I´m not thinking of at the moment?

Is this a supported configuration for a longer time?

The background is that we have 10 hosts (all at ESXi 5.1 at the moment) and three of them are not supported to run ESXi 6, only 5.5U2 and will be replaced in the next year.

Thanks in advance for any answers!

Kind regards,

Paul