Someone pointed out a shocking fact in LET that KVM, the new popular virtualization type, can be over-committed even more then the infamous OpenVZ
The KVM hypervisor supports overcommitting CPUs and overcommitting memory. Overcommitting is allocating more virtualized CPUs or memory than there are physical resources on the system. With CPU overcommit, under-utilized virtualized servers or desktops can run on fewer servers which saves power and money.
Gee. It has been a while since I’ve last written here, and it will be a while again for my next post as I will be on holidays from next Monday (visiting families in Hong Kong and Taiwan). Let me share one small utility program that I wrote quite a while ago.
We all know that the Linux command free(1) is pretty useless inside an OpenVZ VE, even those with meminfo virtualised. So I basically wrote this little util to grab the data from the dreadful user_beancounters and format them into something useful. It’s written in C and only depends on libc so it’s pretty light weight. It also does a little bit of analysis instead of just dumping the data, which I will explain later on.
Update (26-Aug-2010): From my experience, they have very huge iowait and hence I/O problems on their VPS servers. You have to wait for like 10-15 seconds for a ‘uptime’ command to execute which is pretty pathetic. So in my opinion, it was useless for me.