persistence type for ssh vip

You cannot use Cookie based persistence for SSH, because Cookies are a specific feature to HTTP protocol.

With SSH, I think you have to use source IP persistence. I'm wondering, why do you need to use persistence? SSH connections tend to be long-lived, and If you're load-balancing some SSH servers, then I have to assume that it means each pool member is identical, and it doesn't matter which server the user connects to, which makes me wonder why you need persistence.