Thursday, December 20, 2018

Clustering & VM Monitoring

Shall we enable VM (and APP) Monitoring in the cluster settings? It's a big challenge for all virtual admins and countermeasures for answering to this big question, is a real matter.
VMware Tools is an important part of VM setup and for some reason it's necessary to install it on every guest OS (Windows, Linux and etc), because of it's role for time synchronization, better device detection and sending heartbeats. When you decide to enable VM monitoring in the cluster level, it will check heartbeat recieving from each VM. If there is no heartbeats or any network/storage traffics from VM (after default 2 min by clustering advanced options "das.iostatsInterval") VM will be restart but for confronting fault VM restarting, it will do it ONLY 3 times for each hour.
So we should ask ourselves in what situations it can be happened? and why VMware Tools shouldn't work? Generally Blue Screen states or any system faults can cause it. so it's better to reset the VM. As the VMware said, there is 3 states (Low/ Medium/ High) options that will configure 4 below custom settings:
1. Failure interval: It's about heartbeat recieving interval, so after this time HA will restart the VM.
2. Minimum Uptime: HA waiting time before VM startup and it's actions. (any heartbeat, storage, network traffics)
3. Maximum per-VM resets: I explained it before ;)
4. Maximum resets time window: Settings 3 will be executed on this time duration. (per hour)

Thanks to GS Khalsa for his related post on VMware.

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