It is extremely easy to add a server just for Indexing, but is that really beneficial. Is Indexing a bottleneck on the current server? To give an educated answer we need to know how many users (daily archive volume),server specs (CPU/RAM/Virtual?), what problem are you trying to solve, etc...
1. Yes it is possible
2. No, you for example cant have two archiving tasks for the same Exchange server.
These answers are pretty generally.
If you want more detailleid information, you need to let us know what you are trying to aim at.
currently we are running EV 10 on single server(and different SQL server) and now facing performance issue while searching .
we are thinking of adding new server for indexing only.
current user count is 750.
What are the speof the server and what type of storage? 750 users is well under any capacity issues for most servers. CPU, memory, virtual?, storage type, etc... With only 750 users I wouldn't expect to need a 2nd server.