Comment by littlestymaar
1 year ago
Except you don't have 3 hosts but 3 thousands, and during the time you're stopping the 9 VMs somebody else is starting 5 or 15 new ones!
Yes it is similar to memory fragmentation in some way, but your argument is like saying an integer stored on the heap costs a full memory page! You realize that it's nonsense. Sure in extreme edge cases it can, but that's not a good metric to know the memory footprint of an integer!
Being able to move VMs is nice as it allows more host use, but it's doesn't mean hosts end up with single idle VMs often!
Of course, it's not gonna be common. But it will occasionally happen, in such a large data center.
Then you need to account for their low share in idle VMs when measuring how much electricity it is responsible for. If it's only the case for 1% of the idle VMs, then you need to count only 1% of the electric power of a host per idle VM (+ the small fraction of a host CPU power that an idle VM consumes). In any case, it's going to be very small (~$20/year)[1] and the “it costs them nothing” is a good approximation of that, or at least a much better one that assuming that the cost they charge you reflects an expense on their side (which is the point that was argued by rafram at the very start of this discussion.
[1]: let say 10W, which at $.2 per kWh[2], ends up costing $17.5 for an entire year!
[2]: electricity prices from [here](https://www.eia.gov/electricity/monthly/epm_table_grapher.ph...) $.2 per kWh is slightly above the rates in California and Rhode Island, which is the highest in the US for industrial use.