Ganeti

A cluster virtualization manager.

What can it do?

• Manage clusters of physical machines
• Deploy Xen/KVM/lxc virtual machines on them
  • Live migration
  • Resiliency to failure (data redundancy over DRBD)
  • Cluster balancing
  • Ease of repairs and hardware swaps

Ideas

• Making the virtualization entry level as low as possible
  • Easy to install/manage
  • No specialized hardware needed (eg. SANs)
  • Lightweight (no "expensive" dependencies)
• Scale to enterprise ecosystems
  • Manage symultaneously from 1 to ~200 host machines
  • Access to advanced features (drbd, live migration)
• Be a good open source citizen
  • Design and code discussions are open
  • External contributions are welcome
  • Cooperate with other "big scale" Ganeti users

Terminology

• Node: a virtualization host
• Nodegroup: an omogeneous set of nodes
• Instance: a virtualization guest
• Cluster: a set of nodes, managed as a collective
• Job: a ganeti operation

Technologies

• Linux and standard utils (iproute2, bridge-utils, ssh)
• KVM/Xen/LXC
• DRBD, LVM, or SAN
• Python (plus a few modules)
• socat
• Haskell (optional)

Node roles (management level)

• Master Node
  • runs ganeti-masterd, rapi, noded and confd
• Master candidates
  • have a full copy of the config, can become master
  • run ganeti-confd and noded
• Regular nodes
  • cannot become master
  • get only part of the config
• Offline nodes, are in repair

Node roles (instance hosting level)

• VM capable nodes
  • can run virtual machines
• Drained nodes
  • are being evacuated
• Offlined nodes, are in repair

Initializing your cluster

The node needs to be set up following our installation guide.

gnt-cluster init [-s ip] ... \
  --enabled-hypervisors=kvm cluster

gnt-cluster

Cluster wide operations:

gnt-cluster info
gnt-cluster modify [-B/H/N ...]
gnt-cluster verify
gnt-cluster master-failover
gnt-cluster command/copyfile ...

Adding nodes

gnt-node add [-s ip] node2
gnt-node add [-s ip] node3

Adding instances

# install instance-{debootstrap, image}
gnt-os list
gnt-instance add -t drbd \
  {-n node3:node2 | -I hail } \
  -o debootstrap+default web
ping i0
ssh i0 # easy with OS hooks

gnt-node

Per node operations:

gnt-node remove node4
gnt-node modify \
  [ --master-candidate yes|no ] \
  [ --drained yes|no ] \
  [ --offline yes|no ] node2
gnt-node evacuate/failover/migrate
gnt-node powercycle

gnt-instance

Instance operations:

gnt-instance start/stop i0
gnt-instance modify ... i0
gnt-instance info i0
gnt-instance migrate i0
gnt-instance console i0

-t drbd

DRBD provides redundancy to instance data, and makes it possible to perform live migration without having shared storage between the nodes.

Recovering from failure

# set the node offline
gnt-node modify -O yes node3

Recovering from failure

# failover instances to their secondaries
gnt-node failover --ignore-consistency node3
# or, for each instance:
gnt-instance failover \
  --ignore-consistency web

Recovering from failure

# restore redundancy
gnt-node evacuate -I hail node3
# or, for each instance:
gnt-instance replace-disks \
  {-n node1 | -I hail } web

gnt-backup

Manage instance exports/backups:

gnt-backup export -n node1 web
gnt-backup imoport -t plain \
  {-n node3 | -I hail } --src-node node1 \
  --src-dir /tmp/myexport web
gnt-backup list
gnt-backup remove

htools: cluster resource management

Written in Haskell.

• Where do I put a new instance?
• Where do I move an existing one?
  • hail: the H iallocator
• How much space do I have?
  • hspace: the H space calculator
• How do I fix an N+1 error?
  • hbal: the cluster balancer

Controlling Ganeti

• Command line (*)
• Ganeti Web manager
  • Developed by osuosl.org and grnet.gr
• RAPI (Rest-full http interface) (*)
• On-cluster "luxi" interface (*)
  • luxi is currently json over unix socket
  • there is code for python and haskell

(*) Programmable interfaces

Job Queue

• Ganeti operations generate jobs in the master (with the exception of queries)
• Jobs execute concurrently
• You can cancel non-started jobs, inspect the queue status, and inspect jobs

gnt-job list
gnt-job info
gnt-job watch
gnt-job cancel

'big-scale' features

• Nodegroups (2.4/2.5)
• Routed networking
• vm_capable and master_capable nodes (2.3)
• Job priorities (2.3)
• Out of Band management (2.5)
• Cluster merger

gnt-group

Managing node groups:

gnt-group add
gnt-group assign-nodes
gnt-group evacuate
gnt-group list
gnt-group modify
gnt-group remove
gnt-group rename
gnt-instance change-group

Other recent improvements

• New KVM features (vhost, hugepages) (2.4)
• IPv6 (2.3)
• Privilege separation (2.4)
• Inter-cluster instance move
• SPICE (2.5)
• Master network turnup hooks (2.5)

Future roadmap

• Distributed storage (ceph, sheepdog)
• Better OS installation
• Better self-healing
• KVM enhancements
  • block device migration
  • USB redirect
• Networking enhancements
  • Pool and subnet management
  • Better low-level deployment
• More hypervisors/hv-customizations

Running Ganeti in production

What should you add?

• Monitoring/Automation
  • Check host disks, memory, load
  • Trigger events (evacuate, send to repairs, readd node, rebalance)
  • Automated host installation/setup (config management)
• Self service use
  • Instance creation and resize
  • Instance console access

People running Ganeti

• Google (Corporate Computing Infrastructure)
• grnet.gr (Greek Research & Technology Network)
• osuosl.org (Oregon State University Open Source Lab)
• fsffrance.org (according to docs on their website and trac)
• ...

Conclusion

• Check us out at http://code.google.com/p/ganeti.
• Or just Google "Ganeti".
• Try it. Love it. Improve it. Contribute back (CLA required).

Questions? Feedback? Ideas? Flames?