Is 1 vCPU on Google Compute Engine basically half of 1 physical CPU core?

Question

Google's Machine types page states that:

For the n1 series of machine types, a virtual CPU is implemented as a single hardware hyper-thread on a 2.6 GHz Intel Xeon E5 (Sandy Bridge), 2.5 GHz Intel Xeon E5 v2 (Ivy Bridge)...etc

Assuming that a single physical CPU core with hyper-threading appears as two logical CPUs to an operating system, then if the n1-standard-2 machine that is described as 2 virtual CPUs and 7.5 GB of memory, then this essentially means 1 CPU core, right?

So if I'm trying to follow hardware recommendations for an InfluxDB instance that recommends 2 CPU cores, then I should aim for a Google Compute Engine machine that has 4vCPUs, correct?

Answer 1

Typically when software tells you how many cores they need they don't take hyper-threading into account. Remember, AMD didn't even have that (Hyper-Threading) until very recently. So 2 cores means 2 vCPUs. Yes, a single HT CPU core shows up as 2 CPUs to the OS, but does NOT quite perform as 2 truly independent CPU cores.

Answer 2

That's correct, you should aim for a GCE machine-type that has 4vCPUs... When you're migrating from an on-premises world, you're used to physical cores which have hyperthreading. In GCP, these are called vCPUs or virtual CPUs. A vCPU is equivalent to one hyperthread core. Therefore, if you have a single-core hyperthreaded CPU on premises, that would essentially be two virtual CPUs to one physical core. So always keep that in mind as oftentimes people will immediately do a test. They'll say, "I have a four-cores physical machine and I'm going to run four cores in the cloud" and ask "why their performance isn't the same?!!!"