VMC on AWS Outposts offers several node configurations starting with a minimum of three-node configuration (with one additional dark capacity node) to a maximum of nine nodes (with one additional dark capacity node). The dark capacity is used as an auto-remediation task in case of host failures. However, the replacement of the physical hardware can take up to 48 hours from the time a confirmation has been provided, subject to logistical constraints.
Figure 10.13 – VMC on Outposts single-rack configurations
Depending on the organization footprint, a VMC sizing exercise determines the number of nodes required. Each rack, as denoted in the figure, has one additional node reserved for dark capacity that triggers autoscaling in case of a hardware failure or physical health deterioration of any of the active nodes.
Similar to other hyper-converged infrastructure offerings, a VMC on Outposts rack can only scale out. Additional bare-metal hosts can be added to scale the compute and/or storage capacity. There are some functional restrictions in terms of scaling out. Organizations can pick any of the seven configurations available; however, the rack can be scaled out in increments of three nodes at a time.
Each rack, in addition to the Amazon EC2 i3en.metal server(s), has additional nodes used for LCM functions and a pair of ONDs. For organizations who are looking to scale their VMC infrastructure beyond the maximum capacity of nine nodes in a single rack, there is a multi-rack option that can scale up to a maximum of four racks.
Let us look at the scalability of VMC on AWS Outposts single-rack and multi-rack configurations:
| Single rack | Multi-rack | |
| Rack capacity | Min: Three nodes Max: Nine nodes in a single rack | Min: Three nodes Max: Nine nodes in a single rack |
| Outposts logical unit capacity | Single rack: Maximum of nine active nodes | 16 racks: Maximum of 36 active nodes across 4 racks |
| Number of SDDCs | 1 SDDC, 10 clusters (subject to availability of nodes) | 1 SDDC, 10 clusters (subject to availability of nodes) |
| Connectivity to organization network | A pair of ONDs connect to a pair of CNDs | A pair of ONDs connect to a pair of CNDs for configurations up to four racks For multi-rack configurations, the ONDs in each rack connect to ONDs in all the other racks |
| Service link connectivity to AWS Region | A logical Outposts unit establishes a single service link connection back to the AWS Region, independent of the number of racks in the Outposts logical unit (each rack does not establish its own service link) |
Table 10.9 – Comparing single-rack and multi-rack configurations
Multi-rack network connectivity
A VMC on AWS Outposts multi-rack configuration can accommodate multiple racks, with a maximum capacity of four racks within a single Outposts logical unit. The classification of a logical Outposts unit may vary based on its size and scale, with different categorizations to suit various deployment scenarios.
In a VMC on AWS Outposts multi-rack environment, note the following:
- The ONDs in each rack are redundantly interconnected with the ONDs in the other racks to provide highly available network connectivity between them. AWS is responsible for ensuring network availability within the Outposts infrastructure.
- Both ONDs in each rack are also connected with a pair of CNDs.
- A single service link is established for connectivity back to the AWS Region.
The following diagram shows the VMC on Outposts multi-rack architecture that spans four racks, offering greater capacity and scalability.