What is the best way to set up monitoring of a dedicated server with the possibility of notification?

Question

linux

What is the best way to be aware of the status of a dedicated server with virtual machines on board?
I want to be aware of the failure of software raid 1, the fall of virtual machines, and, perhaps, some other critical processes.
How best to organize it, an email notification will do.
Particularly interested in the state of the raid.
Upd1:
Raid on mdadm .
Virtual machines inside proxmox on openvz .
There is only one physical server so far, so far only notification of a critical situation is required.
Later I will put monitoring on a free virtual machine, one of the reviews below.

Answer 1

raid
interface31.ru/tech_it/2013/12/ubuntu-server-nastr...

Answer 2

The state of the raid can be monitored by mdadm, without any third-party programs at all. Look at its monitor mode, and the config /etc/mdadm.cof or /etc/mdadm/mdadm.conf, depending on the distribution.
For other things, see zabbix or, pardon the expression, nagios.

Answer 3

monit + munin + nagios
monit - will monitor critical processes, and if they are not available, restart. It will also send emails about such incidents
munin - will draw various graphs that sometimes help determine in which "place" the problem
is nagios - monitors anything, and sends an email in case of problems
For a large fleet of servers and virtual machines, I use this bundle , copes with 5+
As for RAID, I use this one https://exchange.nagios.org/directory/Plugins/Oper...

Answer 4

I have mdadm during installation on Ubuntu asking if I want to send notifications to e-mail.