Ceph setup on Centos 7, eternal oom ceph-mon?

Question

linux

This is my first time setting up Ceph, but every time I run ceph-deploy on servers, I make all three monitors. then they become unavailable via ssh for some time, and VNC shows that the OOM-killer has worked.
Servers with 8 gigs of RAM, 2 processors, and 300 gigs of disk.
I didn't even add disks to ceph.
I don’t know what to do yet, suddenly someone has already come across this, tell me someone?