Azure B series VM’s, cheap burstable CPU

The new B series VM is now in preview. These are extremely cheap VM’s that offer burstable CPU performance.

What exactly does that mean? Well, basically you can not run these VM’s at 100% CPU 24/7. The VM CPU will run at a predefined baseline, As you run the VM you acquire credits for every hour of run time. Once enough credits have been acquired the VM can burst up to 100%.

This is very similar to AWS T2 instances and is perfect for small web servers, Dev/Test servers and so on that don’t require high CPU usage. The VM will run most of the time at low CPU usage and if required can burst for a short period of time up to 100% as long as you have the required credit to do so.

The B series VM’s are of course priced accordingly with a 2 Core, 4GB VM priced at$20.09 and a larger 4 Core, 16GB VM priced at just $80.36. These are preview prices and based on past experience we can expect these prices to double when general availability is reached. Even then these are still very low prices.

The following table details the VM specs and time to acquire credits for a full burst.

Size vCPU’s Memory: GiB Local SSD: GiB Base CPU Perf of VM Max CPU Perf of VM Credits Banked / Hour Max Banked Credits
Standard_B1s 1 1 4 10% 100% 6 144
Standard_B1ms 1 2 4 20% 100% 12 288
Standard_B2s 2 4 8 40% 200% 24 576
Standard_B2ms 2 8 16 60% 200% 36 864
Standard_B4ms 4 16 32 90% 400% 54 1296
Standard_B8ms 8 32 64 135% 800% 81 1944

So as you can see for example, the B2s will only supply 40% baseline performance (20% of each core). To burst it requires 864 credits, and for each hour of runtime 36 credits are assigned. meaning that it can burst exactly once every 24 hours of run time. This is the same for all the b series, they can burst to 100% of all cores for one hour after every 20 hours of running.

You can also see the official post here