Hello,
there are two concepts: the mirror group and the mirror port. On the 2530, I don't know how many groups you can do. On the 1910 you can do one, on the 3600 you can do 4, so I guess it's between 1 and 4!
In a specific group, I don't know if there is a maximum number of mirror port. On the 1910, you can put at least 6 ports. One thing to consider is the bandwitch: if you want to monitor 6 or 7 Gb ports on 1 Gb port, I hope the mirror ports don't exceed 10% bandwitch...
Regards,
Alexis