Virtualised architectures
Server consolidation, the hypervisor cluster and its shared storage, live migration, high availability, N+1 sizing, the virtual desktop and hyperconvergence.
- 28 cards
- 6 topics
- Free
The outline, topic by topic
Each topic is weighted the way the exam weighs it.
- Concepts
- Questions
- The numbers
- On the diagram
- Scenarios
- Understand
A few cards from the deck
Server consolidation: what is it?
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Grouping many lightly loaded physical servers onto a few hosts, by turning them into virtual machines.
A server dedicated to a single service stays far from its full capacity most of the time. Grouping saves hardware, space, power and cooling.
In a cluster, what is needed to live-migrate a virtual machine from one host to another without moving its disk?
- Storage both hosts can see, a common network and compatible processors
- A full copy of the machine's disk on the target host, made in advance
- That the machine be shut down cleanly, then restarted on the target host
- A target host with exactly the same amount of memory as the original host
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Storage both hosts can see, a common network and compatible processors
Only memory and processor state are copied while the machine runs; the disk stays in place on the shared storage. Shutting down would describe a cold migration.
A … gives hosts block-level access to storage (Fibre Channel, iSCSI), whereas a … shares it as files (NFS, SMB).
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A SAN gives hosts block-level access to storage (Fibre Channel, iSCSI), whereas a NAS shares it as files (NFS, SMB).
With a SAN the host sees a raw disk that it formats itself; with a NAS it mounts a remote folder. Both suit a hypervisor cluster.
Hypervisor cluster: what is it?
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A set of linked virtualisation hosts, managed together as a common pool of processor and memory in which virtual machines move around.
Machines are no longer tied to a specific host: the cluster places them, rebalances them and restarts them elsewhere after a failure.