Guaranteeing SSH access on a stressed server

I had an issue some time ago with a server in which Apache and Snort was occupying 100% of the processor, making the sshd unresponsive through remote access. I had to go physically to the server to log on a local TTY and then stop apache/snort.

I'm wondering if there's a way of guaranteeing ssh connectivity on a situation of 100% loaded CPU/memory. Setting a "nice" priority would be enough?

Thank you!

Other than using an out-of-band method, there's no way to guarantee that SSH will be available on a fully loaded server. If your service is so loaded that it can't even serve a basic SSH terminal to you, then you have other problems.

Yes, renice and giving it a lower nice value will improve the performance in heavy loads, but instead using something like pam_security (example shown here) will prevent Apache/whatever from becoming unmanageable to begin with.

Your general-purpose solution for this is an out-of-band management tool, like Dell iDRAC, IBM Remote Supervisor, or HP iLO. It can always present a console (whether or not the OS can respond to it depends on your specific situation), and apply desired power states as needed.