Pros and cons for OpenVZ 7 as compared to KVM
I've been curious about OpenVZ, as I never tried it before (only ran KVM in VPS'es, and on my local servers/workstations I've been running LXC/LXD, Xen, KVM, VirtualBox, VMware).
After testing a bit these are my initial thought. (I might be wrong.)
- Usually cheap(er than KVM)
- Templates, disk usage lower (<400 MB for Debian 10)
- Lower memory usage, more free memory (running the same processes)
- Theoretically it could/should have lower overhead CPU wise? (I haven't experienced/been able to confirm this.)
- For the provider: Easier to monitor/stop/prevent abuse
- Less options for OS selection (share Linux kernel, can't install BSD etc.)
- Monitoring by provider easier
- Server can more often be a bit heavier utilized/more crowded (?)
- Can't load kernel specific stuff/modules (due to shared kernel)
- Not everything works (as an example, stick with iptables, not nftables, for the time being)
There might also be other limitations I should have mentioned?
One thing I've noticed, is for disk I/O, I get something like this on my OpenVZ 7 instances:
Disk Speed: 1st run : 232 MB/s 2nd run : 684 MB/s 3rd run : 774 MB/s
So, 1st run is much slower than the next. I didn't see that as clearly on a KVM node, but I'm not sure if it's really related to KVM vs. OVZ, maybe it has more to do with caching.
I've also noticed on an OpenVZ 7 instance with 2 vCPU that "multi core" CPU benchmark scores were lower than the single core score. But I have no idea of why, so I'll just mention it in case it's relevant.
All in all, if the price is right, OpenVZ 7 might still be a good alternative, if the limitations is something you can live with.
There much I don't know, so there might be vital points I've missed.