How many databases we can put in mirroring
Microsoft suggests 10 databases to be mirrored in a single instance, but I have seen more. I guess there will be some performance degradation if there are more than 10.
Also if automatic failover happens all db failover start same time ?
Regarding auto failover, it's depends on which database has issues with mirroring.....if you are asking about a scenario where the whole instance going down and each of the mirroring failover to mirror side.....then, I still think it will failover one by one. I did not encounter this scenario....as of now.