internall by Ganeti as an *OpCode* (abbreviation from operation
code). These OpCodes are executed as part of a *Job*. The OpCodes in a
single Job are processed serially by Ganeti, but different Jobs will be
-processed (depending on resource availability) in parallel.
+processed (depending on resource availability) in parallel. They will
+not be executed in the submission order, but depending on resource
+availability, locks and (starting with Ganeti 2.3) priority. An earlier
+job may have to wait for a lock while a newer job doesn't need any locks
+and can be executed right away. Operations requiring a certain order
+need to be submitted as a single job, or the client must submit one job
+at a time and wait for it to finish before continuing.
For example, shutting down the entire cluster can be done by running the
command ``gnt-instance shutdown --all``, which will submit for each
.. warning:: Do not use the Xen or KVM commands directly to stop
instances. If you run for example ``xm shutdown`` or ``xm destroy``
- on an instance Ganeti will automatically restart it (via the
- :command:`ganeti-watcher` command which is launched via cron).
+ on an instance Ganeti will automatically restart it (via
+ the :command:`ganeti-watcher` command which is launched via cron).
Querying instances
~~~~~~~~~~~~~~~~~~
be seamless for the instance. For more than one disk, just pass another
disk parameter (e.g. ``--disk 1:adopt=...``).
+Instance kernel selection
++++++++++++++++++++++++++
+
+The kernel that instances uses to bootup can come either from the node,
+or from instances themselves, depending on the setup.
+
+Xen-PVM
+~~~~~~~
+
+With Xen PVM, there are three options.
+
+First, you can use a kernel from the node, by setting the hypervisor
+parameters as such:
+
+- ``kernel_path`` to a valid file on the node (and appropriately
+ ``initrd_path``)
+- ``kernel_args`` optionally set to a valid Linux setting (e.g. ``ro``)
+- ``root_path`` to a valid setting (e.g. ``/dev/xvda1``)
+- ``bootloader_path`` and ``bootloader_args`` to empty
+
+Alternatively, you can delegate the kernel management to instances, and
+use either ``pvgrub`` or the deprecated ``pygrub``. For this, you must
+install the kernels and initrds in the instance and create a valid GRUB
+v1 configuration file.
+
+For ``pvgrub`` (new in version 2.4.2), you need to set:
+
+- ``kernel_path`` to point to the ``pvgrub`` loader present on the node
+ (e.g. ``/usr/lib/xen/boot/pv-grub-x86_32.gz``)
+- ``kernel_args`` to the path to the GRUB config file, relative to the
+ instance (e.g. ``(hd0,0)/grub/menu.lst``)
+- ``root_path`` **must** be empty
+- ``bootloader_path`` and ``bootloader_args`` to empty
+
+While ``pygrub`` is deprecated, here is how you can configure it:
+
+- ``bootloader_path`` to the pygrub binary (e.g. ``/usr/bin/pygrub``)
+- the other settings are not important
+
+More information can be found in the Xen wiki pages for `pvgrub
+<http://wiki.xensource.com/xenwiki/PvGrub>`_ and `pygrub
+<http://wiki.xensource.com/xenwiki/PyGrub>`_.
+
+KVM
+~~~
+
+For KVM also the kernel can be loaded either way.
+
+For loading the kernels from the node, you need to set:
+
+- ``kernel_path`` to a valid value
+- ``initrd_path`` optionally set if you use an initrd
+- ``kernel_args`` optionally set to a valid value (e.g. ``ro``)
+
+If you want instead to have the instance boot from its disk (and execute
+its bootloader), simply set the ``kernel_path`` parameter to an empty
+string, and all the others will be ignored.
+
Instance HA features
--------------------
Note that the set of characters present in a tag and the maximum tag
length are restricted. Currently the maximum length is 128 characters,
there can be at most 4096 tags per object, and the set of characters is
-comprised by alphanumeric characters and additionally ``.+*/:-``.
+comprised by alphanumeric characters and additionally ``.+*/:@-``.
Operations
++++++++++
top-level queue directory, or look at its contents (it's a
JSON-formatted file).
+Special Ganeti deployments
+--------------------------
+
+Since Ganeti 2.4, it is possible to extend the Ganeti deployment with
+two custom scenarios: Ganeti inside Ganeti and multi-site model.
+
+Running Ganeti under Ganeti
++++++++++++++++++++++++++++
+
+It is sometimes useful to be able to use a Ganeti instance as a Ganeti
+node (part of another cluster, usually). One example scenario is two
+small clusters, where we want to have an additional master candidate
+that holds the cluster configuration and can be used for helping with
+the master voting process.
+
+However, these Ganeti instance should not host instances themselves, and
+should not be considered in the normal capacity planning, evacuation
+strategies, etc. In order to accomplish this, mark these nodes as
+non-``vm_capable``::
+
+ node1# gnt-node modify --vm-capable=no node3
+
+The vm_capable status can be listed as usual via ``gnt-node list``::
+
+ node1# gnt-node list -oname,vm_capable
+ Node VMCapable
+ node1 Y
+ node2 Y
+ node3 N
+
+When this flag is set, the cluster will not do any operations that
+relate to instances on such nodes, e.g. hypervisor operations,
+disk-related operations, etc. Basically they will just keep the ssconf
+files, and if master candidates the full configuration.
+
+Multi-site model
+++++++++++++++++
+
+If Ganeti is deployed in multi-site model, with each site being a node
+group (so that instances are not relocated across the WAN by mistake),
+it is conceivable that either the WAN latency is high or that some sites
+have a lower reliability than others. In this case, it doesn't make
+sense to replicate the job information across all sites (or even outside
+of a “central” node group), so it should be possible to restrict which
+nodes can become master candidates via the auto-promotion algorithm.
+
+Ganeti 2.4 introduces for this purpose a new ``master_capable`` flag,
+which (when unset) prevents nodes from being marked as master
+candidates, either manually or automatically.
+
+As usual, the node modify operation can change this flag::
+
+ node1# gnt-node modify --auto-promote --master-capable=no node3
+ Fri Jan 7 06:23:07 2011 - INFO: Demoting from master candidate
+ Fri Jan 7 06:23:08 2011 - INFO: Promoted nodes to master candidate role: node4
+ Modified node node3
+ - master_capable -> False
+ - master_candidate -> False
+
+And the node list operation will list this flag::
+
+ node1# gnt-node list -oname,master_capable node1 node2 node3
+ Node MasterCapable
+ node1 Y
+ node2 Y
+ node3 N
+
+Note that marking a node both not ``vm_capable`` and not
+``master_capable`` makes the node practically unusable from Ganeti's
+point of view. Hence these two flags should be used probably in
+contrast: some nodes will be only master candidates (master_capable but
+not vm_capable), and other nodes will only hold instances (vm_capable
+but not master_capable).
+
+
Ganeti tools
------------
Other Ganeti projects
---------------------
-There are two other Ganeti-related projects that can be useful in a
-Ganeti deployment. These can be downloaded from the project site
-(http://code.google.com/p/ganeti/) and the repositories are also on the
-project git site (http://git.ganeti.org).
+Below is a list (which might not be up-to-date) of additional projects
+that can be useful in a Ganeti deployment. They can be downloaded from
+the project site (http://code.google.com/p/ganeti/) and the repositories
+are also on the project git site (http://git.ganeti.org).
NBMA tools
++++++++++
ganeti-htools
+++++++++++++
-The ``ganeti-htools`` software consists of a set of tools:
-
-- ``hail``: an advanced iallocator script compared to Ganeti's builtin
- one
-- ``hbal``: a tool for rebalancing the cluster, i.e. moving instances
- around in order to better use the resources on the nodes
-- ``hspace``: a tool for estimating the available capacity of a cluster,
- so that capacity planning can be done efficiently
+Before Ganeti version 2.5, this was a standalone project; since that
+version it is integrated into the Ganeti codebase (see
+:doc:`install-quick` for instructions on how to enable it). If you run
+an older Ganeti version, you will have to download and build it
+separately.
For more information and installation instructions, see the README file
in the source archive.
projects / ganeti-local / blobdiff