In this case study we discuss how Alice and Bob would architect their clouds with respect to instance entropy, scheduling instances, trusted images, and instance migrations.

Alice has a need for lots of high quality entropy in the instances. For this reason, she decides to purchase hardware with Intel Ivy Bridge chip sets that support the RdRand instruction on each compute node. Using the entropy gathering daemon (EGD) and LibVirt's EGD support, Alice ensures that this entropy pool is distributed to the instances on each compute node. For instance scheduling, Alice uses the trusted compute pools to ensure that all cloud workloads are deployed to nodes that presented a proper boot time attestation. Alice decides to disable user permissions for image uploading to help ensure that the images used in the cloud are generated in a known and trusted manner by the cloud administrators. Finally, Alice disables instance migrations as this feature is less critical for the high performance application workloads expected to run in this cloud. This helps avoid the various security concerns related to instance migrations.

Bob is aware that entropy will be a concern for some of his customers, such as those in the financial industry. However, due to the added cost and complexity, Bob has decided to forgo integrating hardware entropy into the first iteration of his cloud. He adds hardware entropy as a fast-follow to do for a later improvement for the second generation of his cloud architecture. Bob is interested in ensuring that customers receive a high quality of service. He is concerned that providing too much explicit user control over instance scheduling could negatively impact the quality of service. So he disables this feature. Bob provides images in the cloud from a known trusted source for users to use. Additionally, he also allows users to upload their own images. However, users cannot generally share their images. This helps prevent a user from sharing a malicious image, which could negatively impact the security of other users in the cloud. For migrations, Bob wants to enable secure instance migrations in order to support rolling upgrades with minimal user downtime. Bob ensures that all migrations occur on an isolated VLAN. He plans to defer implementing encrypted migrations until this is better supported in nova client tools. However, he makes a note to track this carefully and switch to encrypted migrations as soon as possible.