In Microsoft Azure, What server size/series uses credits and slows down if the credits run out?

In Microsoft Azure, What server size/series uses credits and slows down if the credits run out?

• F series
• D series
• B series
• A series

EXPLANATION

 B-series 

These are known as “burstable” VMs.  They are very useful but the way they work is a bit complicated.  B-series are used for non-CPU intensive workloads (e.g. domain controllers, file servers) and cost about 50% of an equivalently sized Ds-series VM.  The reason they’re cheaper is because Azure imposes a quota on how much of the total CPU cores can be used.  This quota is usually a fraction of the total available CPU. 
For instance, B2m’s quota is 60% of a single CPU, which is 30% of the 2 CPUs visible in the VM.  Every second that the VM is using less than its quota (less than 60% of a single CPU) it is “banking credits”.  These banked credits can be used to burst up to the total available CPUs (100% of 2 CPUs, in this example) when needed.  While bursting, the VM is consuming its banked credits.  Once credits run out, the VM’s CPU utilization is throttled down to its 60% quota.
Why use B-series VMs?  They are cheaper.  For approximately the same price that you would pay for a Ds-series VM, you can get a B-series with double the CPUs and double the RAM.  However, they should only be used for workloads that are either not CPU intensive or “bursty”, meaning they only occasionally need all the CPU but most of the time the CPU is idle. 
For instance, an Active Directory domain controller is not utilizing its CPU very heavily on a regular basis.  However, when Windows Updates run, the VM will use all its available CPU horsepower.  B-series are perfect for Domain Controllers since they bank credits while idle and then consume them when needed to update or do some other CPU intensive task.

• Purpose: General, non-CPU intensive workloads (e.g. AD domain controllers, file servers) 
• CPU clock speed: varies 
• vCPU-to-RAM ratio: varies from 1:1 to 1:4 for VMs larger than B2s 
• Storage supported: Standard and Premium 
• Approximate average list price per CPU: ranges from $13/month to $40/month 

Nerdio Tips:

• Don’t use B-series VMs for CPU intensive workloads 
• When a B-series VM is first provisioned, it doesn’t have any banked credits and is subject to its quota limit on the CPU, which means it’s slow.  Once the VM is running idle for some time, credits get banked and the VM performance improves when it needs to burst. 
• Don’t shut down B-series VMs overnight when they are not in use.  This will not allow the VMs to bank credits for the following day of usage.