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Revamp about and architecture docs

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Makes these a little simpler to follow and provides some more up-to-date
information based on recent tests and developments.
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Joshua Boniface
2021-10-04 01:42:08 -04:00
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@ -19,21 +19,21 @@ This document contains information about the project itself, the software stack,
## Project Motivation
Server management and system administration have changed significantly in the last decade. Computing as a resource is here, and software-defined is the norm. Gone are the days of pet servers, of tweaking configuration files by hand, and of painstakingly installing from ISO images in 52x CD-ROM drives. This is a brave new world.
Server administration has changed significantly in recent decades. Computing-as-a-resource and software-defined infrastructure is now the norm, and the days of pet servers, painstaking manual configurations, and installing from CR-ROM ISOs is long gone. This is a brave new world.
As part of this trend, the rise of IaaS (Infrastructure as a Service) has created an entirely new way for administrators and, increasingly, developers, to interact with servers. They need to be able to provision virtual machines easily and quickly, to ensure those virtual machines are reliable and consistent, and to avoid downtime wherever possible. Even in a world of containers, VMs are still important, and are not going away, so some virtual management solution is a must.
As part of these trends, Infrastructure-as-a-Service (IaaS) has become a critical component of server administration. Administrators and developers are increasingly interfacing with their infrastructure via programmable APIs and software tools, and automation is a hard requirement. While Container infrastructure like Docker and Kubernetes has become more and more popular in this space, Virtual Machines (VMs) are still a very common feature and do not seem to be going anywhere any time soon.
However, the current state of this ecosystem is lacking. At present there are 3 primary categories: the large "Stack" open-source projects, the smaller traditional "VM management" open-source projects, and the entrenched proprietary solutions.
However, the current state of the free and open source virtualization ecosystem is lacking.
At the high end of the open-source ecosystem, are the "Stacks": OpenStack, CloudStack, and their numerous "vendorware" derivatives. These are large, unwieldy projects with dozens or hundreds of pieces of software to deploy in production, and can often require a large team just to understand and manage them. They're great if you're a large enterprise, building a public cloud, or have a team to get you going. But if you just want to run a small- to medium-sized virtual cluster for your SMB or ISP, they're definitely overkill and will cause you more headaches than they will solve long-term.
At the lower end, projects like ProxMox provide an easy way to administer small virtualization clusters, but these projects tend to lack advanced redundancy facilities that are built-in by default. While there are some new contenders in this space, such as Harvester, the options are limited and their feature-sets and tool stacks can be cumbersome or unproven.
At the low end of the open source ecosystem, are what I call the "traditional tools". The biggest name in this space is ProxMox, though other, mostly defunct projects like Ganeti, tangential projects like Corosync/Pacemaker, and even traditional "I just use scripts" methods fit as well. These projects are great if you want to run a small server or homelab, but they quickly get unwieldy, though for the opposite reason from the Stacks: they're too simplistic, designed around single-host models, and when they provide redundancy at all it is often haphazard and nowhere near production-grade.
At the higher end, very large projects like OpenStack and CloudStack provide very advanced functionality, but these project are sprawling and complicated for Administrators to use, and are very focused on large enterprise deployments, not suitable for smaller clusters and teams.
Finally, the proprietary solutions like VMWare and Nutanix have entrenched themselves in the industry. They're excellent pieces of software providing just about anything you would need, but this comes at a significant cost, both in terms of money and also in software freedom and vendor lock-in. The licensing costs of Nutanix for instance can often make even enterprise-grade customers' accountants' heads spin.
Finally, proprietary solutions dominate this space. VMWare and Nutanix are the two largest names, with these products providing functionality for both small and large clusters, but proprietary software limits both flexibility and freedom, and the costs associated with these solutions is immense.
PVC seeks to bridge the gaps between these 3 categories. It is fully Free Software like the first two categories, and even more so - PVC is committed to never be "open-core" software and to never hide a single feature behind a paywall; it is able to scale from very small (1 or 3 node) clusters up to a dozen or more nodes, bridging the first two categories as effortlessly as the third does; it makes use of a hyperconverged architecture like ProxMox or Nuntanix to avoid wasting hardware resources on dedicated controller, hypervisor, and storage nodes; it is redundant at every layer from the ground-up, something that is not designed into any other free solution, and is able to tolerate the loss any single disk or entire node with barely a blip, all without administrator intervention; and finally, it is designed to be as simple to use as possible, with an Ansible-based node management framework, a RESTful API client interface, and a consistent, self-documenting CLI administration tool, allowing an administrator to create and manage their cluster quickly and simply, and then get on with more interesting things.
PVC aims to bridge the gaps between these three categories. Like the larger FLOSS and proprietary projects, PVC can scale up to very large cluster sizes, while remaining usable even for small clusters as well. Like the smaller FLOSS and proprietary projects, PVC aims to be very simple to use, with a fully programmable API, allowing administrators to get on with more important things. Like the other FLOSS solutions, PVC is free, both as in beer and as in speech, allowing the administrator to inspect, modify, and tailor it to their needs. And finally, PVC is built from the ground-up to support host-level redundancy at every layer, rather than this being an expensive, optional, or tacked on feature.
In short, it is a Free Software, scalable, redundant, self-healing, and self-managing private cloud solution designed with administrator simplicity in mind.
In short, it is a Free Software, scalable, redundant, self-healing, and self-managing private cloud solution designed with administrator simplicity in mind.
## Building Blocks
@ -45,9 +45,9 @@ To manage cluster state, PVC uses Zookeeper. This is an Apache project designed
Additional relational database functionality, specifically for the managed network DNS aggregation subsystem and the VM provisioner, is provided by the PostgreSQL database system and the Patroni management tool, which provides automatic clustering and failover for PostgreSQL database instances.
Node network routing for managed networks providing EBGP VXLAN and route-learning is provided by FRRouting, a descendant project of Quaaga and GNU Zebra. Upstream routers can use this interface to learn routes to cluster networks as well.
Node network routing for managed networks providing EBGP VXLAN and route-learning is provided by FRRouting, a descendant project of Quaaga and GNU Zebra. Upstream routers can use this interface to learn routes to cluster networks as well. PVC also makes extensive use of the standard Linux `iprouting` stack.
The storage subsystem is provided by Ceph, a distributed object-based storage subsystem with extensive scalability, self-managing, and self-healing functionality. The Ceph RBD (RADOS Block Device) subsystem is used to provide VM block devices similar to traditional LVM or ZFS zvols, but in a distributed, shared-storage manner.
The storage subsystem is provided by Ceph, a distributed object-based storage subsystem with proven stability, extensive scalability, self-managing, and self-healing functionality. The Ceph RBD (RADOS Block Device) subsystem is used to provide VM block devices similar to traditional LVM or ZFS zvols, but in a distributed, shared-storage manner.
All the components are designed to be run on top of Debian GNU/Linux, specifically Debian 10.x "Buster" or 11.x "Bullseye", with the SystemD system service manager. This OS provides a stable base to run the various other subsystems while remaining truly Free Software, while SystemD provides functionality such as automatic daemon restarting and complex startup/shutdown ordering.