[ACI] Resource buffer

Author: dlepow

articles/container-instances/container-instances-container-groups.md

@@ -1,6 +1,6 @@
 ---
 title: Introduction to container groups
-description: Learn about container groups in Azure Container Instances, a collection of instances that share a lifecycle and resources such as storage and network
+description: Learn about container groups in Azure Container Instances, a collection of instances that share a lifecycle and resources such as CPUs, storage, and network
 ms.topic: article
 ms.date: 11/01/2019
 ms.custom: mvc
@@ -53,6 +53,9 @@ For example, in a group with two container instances each requesting 1 CPU, one
 
 In this scenario, you could set a resource limit of 2 CPUs for the container instance. This configuration allows the container instance to use up to the full 2 CPUs if available.
 
+> [!NOTE]
+> A small amount of a container group's resources is used by the service's underlying infrastructure. Your containers will be able to access most but not all of the resources allocated to the group. For this reason, plan a small resource buffer when requesting resources for containers in the container group.
+
 ### Minimum and maximum allocation
 
 * Allocate a **minimum** of 1 CPU and 1 GB of memory to a container group. Individual container instances within a group can be provisioned with less than 1 CPU and 1 GB of memory. 

articles/container-instances/container-instances-faq.md

@@ -50,10 +50,13 @@ Use the smallest image that satisfies your requirements. For Linux, you could us
 
 ### How many cores and memory should I allocate for my containers or the container group?
 
-This really depends on your workload. Start small and test performance to see how your containers do. [Monitor CPU and memory resource usage](container-instances-monitor.md), and then add cores or memory based on the kind of processes that you deploy in the container. 
+This really depends on your workload. Start small and test performance to see how your containers do. [Monitor CPU and memory resource usage](container-instances-monitor.md), and then add cores or memory based on the kind of processes that you deploy in the container.
 
 Make sure also to check the [resource availability](container-instances-region-availability.md#availability---general) for the region you are deploying in for the upper bounds on CPU cores and memory available per container group. 
 
+> [!NOTE]
+> A small amount of a container group's resources is used by the service's underlying infrastructure. Your containers will be able to access most but not all of the resources allocated to the group. For this reason, plan a small resource buffer when requesting resources for containers in the container group.
+
 ### What underlying infrastructure does ACI run on?
 
 Azure Container Instances aims to be a serverless containers-on-demand service, so we want you to be focused on developing your containers, and not worry about the infrastructure! For those that are curious or wanting to do comparisons on performance, ACI runs on sets of Azure VMs of various SKUs, primarily from the F and the D series. We expect this to change in the future as we continue to develop and optimize the service.