One of the primary appeals of the VMware Cloud on AWS service is the ability to focus on value-generating work, leaving the mundane day-to-day to VMware. Delivering on this promise requires a thoughtful segmentation of duties. This pattern is repeated throughout the stack to include one of the more dominant disciplines within the datacenter, storage. Storage management in the VMware Cloud on AWS service empowers customers to shift their focus from the storage platform to the actual applications and data.
How does it work?
VMware is responsible for and in control of the vSAN cluster. Customers declare the type and scale of the desired cluster. Once provisioned, each node in the cluster contributes capacity to the vSAN datastore. The administrator then controls via policy how this capacity is consumed. VMware sets an appropriate default but does not prevent the creation or assignment of custom policies. As a result of this empowerment, there is one essential aspect that is under the customer's control, availability.
By default, the vSAN Default Datastore policy is configured with an appropriate policy. Customers who wish to manage their footprint, the full portfolio and potential of vSAN Storage Policy-Based Management remain available within VMC. Customers can define custom policies that conform to the needs of the underlying application; employing Erasure-Coding where needed to control capacity consumption or a myriad of other options. In practice, we see customers establish a commonsense baseline and then layer in specific policies for individual workloads or data classifications.
This flexible system empowers customers to shape how a VMware Cloud on AWS cluster is consumed without needing to get into the minutia of day-to-day vSphere/vSAN management. That's not to say there aren't a few considerations or rules of the road one must follow within the service.
Minimum Policy configuration
The VMware Cloud on AWS Service Definition and SLA outline the expectations for both VMware and our customers. For any workload to qualify for SLA credits, the configured storage policy must meet the minimum required failures to tolerate. This minimum is based on vSAN’s ability to survive a failure within the AWS cloud. Customers are empowered to opt-out of the SLA and choose to accept the risk, protecting from permanent data loss by other means.
The AWS i3.metal EC2 hosts use local NVMe media. The VMware Cloud service uses a very sophisticated auto-remediation process that replaces any problematic hosts at the first sign of trouble. This proactive system enables customers to run clusters at capacity without the need for a spare or maintenance host, by relying on the cloud to add those hosts when they're needed. However, this network-intensive replacement process can take some time on larger clusters. To protect from a potential double failure scenario, the service requires clusters with more than 6 hosts in a single AZ to use a storage policy capable of surviving 2 failures. Customers are responsible for changing the policy configuration in such scenarios.
Elastic vSAN (r5.metal)
Elastic vSAN uses a different kind of EC2 Nitro instance. These instances are diskless and use Elastic Block Store volumes as local storage. The service has been optimized to use the additional resiliency of EBS to reduce rebuild times. We do this by moving the EBS volumes themselves instead of the data contained therein. This combination allows VMware to protect all Elastic vSAN instances with a 1 Failure to tolerate. Customers may still choose to use a higher availability policy to protect availability gaps caused by unplanned host replacement, but it is not compelled by the SLA.
In addition to the baseline availability requirements, the service also requires a minimum level of free space to be maintained at all times. For VMware to guarantee operational availability, the cluster must have sufficient free capacity to rebuild into in the event of an unplanned failure and or massive policy change. The Service Definition defines that every VMware Cloud on AWS cluster must maintain 25% free space at all times. To ensure availability the service automatically adds a node via Elastic DRS at 20% free space.
The VMware Cloud on AWS service enables customers to focus on value-generating work. Trusting in VMware to maintain the cluster, while retaining ownership for and control over the data itself. This powerful combination empowers customers without restricting capabilities or increasing complexity thanks to vSAN and Storage Policy-Based Management.
To view the latest status of features for VMware Cloud on AWS, visit https://cloud.vmware.com/vmc-aws/roadmap.
- You can learn more about the service at https://cloud.vmware.com/vmc-aws
- Watch: VMware Cloud on AWS: Overview
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- Obtain our VMware Cloud on AWS Solution Brief and TCO 1-pager
- Follow our release notes on continuing updates here: docs.vmware.com/en/VMware-Cloud-on-AWS/0/rn/vmc-on-aws-relnotes.html
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