One of the fun elements of being briefed about a product that is not yet released, and probably has not had its form finalized, is that only part of the product is revealed. This week at Pure Accelerate the Pure Cloud Block Store (CBS) was launched in its production form. The CBS is an implementation of the Flash Array that runs on AWS rather than on-premises. In my earlier post about CBS, I talked about the storage architecture, S3 object storage for performance, EC2 Instance Store for a read cache and EBS IO1 for the write buffer. This storage architecture remains in place in the CBS but is not attached to the controller as I thought. The EC2 instances that have the IO1 and Instance Store are called Virtual Disks. The basic CBS has seven of these as a “disk shelf.” The controllers in CBS have boot volumes, all the data and metadata storage are in the Virtual Disks, which is the same architecture as a physical Flash Array. One other element that I did not foresee is a DynamoDB table to store system configuration, rather than having this configuration on the disks.
Deploying the CBS is done through the AWS Marketplace, which in turn deploys a Cloud Formation Template (CFT) into your VPC. This first implementation does not appear to offer a large amount of customization; the number and size of EC2 instances are fixed in the CFT. It does seem that the inflexibility is in part due to how the AWS marketplace works and that post-deployment reconfiguration should be possible. Another option is to customize the CFT yourself before deploying the CBS.
In the diagram of the CFT, you can see the private subnet that connects the virtual disk EC2 instances and the controller instances, along with a Clients subnet where EC2 instances can consume the CBS storage. Notice that there is a public subnet with a NAT gateway, this allows the CBS to phone-home to Pure1 for remote management and support. Also, notice that there are VPC endpoints for both S3 and DynamoDB, these allow the CBS to access AWS services without going to the public IP addresses. These endpoints keep data access inside the private subnet in the VPC, which is good for security and performance. Pure’s use of AWS features and services shows a great understanding of the platform and should help customers get value from CBS without excessive cost.
© 2019, Alastair. All rights reserved.