Simple KVM service documentation

Guests : Information on managing KVM guests
Hosts : Information on managing KVM hosts

What is the KVM service?

It's some servers on which computing staff can run virtual machines (VMs). We use a lot of VMs - it's cheaper and quicker than buying a real machine each time we need one, and we don't have room for all those machines anyway.

Which KVM server do I choose?

If it's for a student project, put it on amarela.

If it's a little test VM, put it on azul.

Other VMs go on clavichord or harpsichord, as they're the newest and least loaded of the KVM servers.

KVM Server reboots

KVM host reboots will be announced a week in advance, and these reboots will only be cancelled for very good reason. Reboots won't go ahead until the details have been signed off by each affected unit on the KVM server scheduled downtime page. The reboots will take place early morning (8am). Only very critical services will be migrated to another server - if possible. Other guests will be suspended or rebooted depending on what KVM allows.

The MP unit will try and minimize the number of KVM host reboots - we expect 2-3 reboots per host per year.

(Agreed at the 25/09/13 operational meeting)

There's a page which details scheduled downtime for the KVM servers.

Host click host for details	Memory (GB)	Storage Locations see below	Site	Hot Migration see below	Comments
girassol	256	local disk (gp3, gp1)	Forum	Yes, between girassol, gaivota and piano.	SL7. Fully supported. Has many more CPU cores than the other servers, but they're a little slower. Not for student projects.
gaivota	256	local disk (vp3, vp1)	Forum		SL7. Fully supported. Not for student projects.
piano	376	local disk (pp1)	Forum		SL7. Fully supported. Not for student projects.
banjo	192	local disk (bp1)	Appleton Tower	Yes, between banjo, mandolin and azul.	SL7. Fully supported. Not for student projects.
mandolin	192	local disk (wp1)	Appleton Tower		SL7. Fully supported. Not for student projects.
azul	128	local disk (ap1)	Appleton Tower		SL7. Use at your own risk. Azul is our test KVM server. It may occasionally be rebooted at short notice. Not for student projects.
amarela	128	local disk (ap1)	JCMB	Yes, between clavichord and harpsichord, and also to/from amarela in emergencies.	SL7. Fully supported. Put your student projects here!
clavichord	256	local disk (cp1)	JCMB		SL7. Fully supported. Not for student projects.
harpsichord	256	local disk (hp1)	JCMB		SL7. Fully supported. Not for student projects.

About Storage Locations

A guest's disk space is created in one of the host's storage pools. A pool can be a local directory, an NFS mounted directory or an LVM volume group. We are using LVM volume groups for our KVM hosts.

To see how much space is available in a pool, login to the host server, nsu then /sbin/pvs. The "VG" column in the output is a shortened form of the pool's name, so it should be obvious which pool is which.

About Migration

Hot migration is where a virtual machine is moved to another host while it's still up and running. The virtual machine and its users are unaware of the move; it just keeps on running. There is no downtime. Hot migration works between KVM hosts which are at the same site - because they need to be carrying the right subnet. Please ask the MPU to do the migration for you, don't try it yourself.

Bridges

A KVM host has one bridge interface per subnet that it supports. The default bridge, named br0, will be connected to the same subnet as the KVM host. Other bridges are named eg br33 for wire-s33. Note that the KVM hosts are not, themselves, multi-homed: this makes it much easier to add and remove subnets for the KVM guests.

Further KVM documentation

• Red Hat Enterprise Linux 7 documentation list including
  • Virtualization Getting Started Guide
  • Virtualization Deployment and Administration Guide
  • Virtualization Tuning and Optimization Guide
  • Virtualization Security Guide
• virt-manager home page