How do I manage multiple servers effectively ?

[Finley]

We are experiencing an increasing demand since the new year, where the demand seems to be more for linux systems. Currently we are using a bunch of custom bash scripts per customer + ssh keys to login and manage multiple systems but somehow it's becoming difficult doing that looking at the volume of requests that are pouring in.

We've been using XShell, but is there a better one that you can recommend us to use ? My prime requirement is that, I should be able to manage a greater number of systems with best efficiency and should log me in fast.