Commit 9256e36a authored by Iustin Pop's avatar Iustin Pop
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Small documentation update

parent e2fa2baf
Ganeti Cluster tools (htools)
=============================
Ganeti Cluster tools (ganeti-htools)
====================================
These are some simple cluster tools for fixing common problems. Right
now N+1 and rebalancing are included. Starting with version 0.1.0,
only Ganeti 2.0 is supported.
These are some simple cluster tools for fixing common allocation
problems on Ganeti 2.0 clusters.
Note that these tools are most useful for bigger cluster sizes
(e.g. more than five or ten machines); at lower sizes, the
computations they do can also be done manually.
Available tools
---------------
Cluster rebalancer
------------------
~~~~~~~~~~~~~~~~~~
Compared to the N+1 solver, the rebalancer uses a very simple algorithm:
repeatedly try to move each instance one step, so that the cluster score
The rebalancer uses a simple algorithm to try to get the nodes of the
cluster as equal as possible in their resource usage. It tries to
repeatedly move each instance one step, so that the cluster score
becomes better. We stop when no further move can improve the score.
For algorithm details and usage, see the man page hbal(1).
Cluster N+1 solver
------------------
~~~~~~~~~~~~~~~~~~
This program runs a very simple brute force algorithm over the instance
placement space in order to determine the shortest number of replace-disks
needed to fix the cluster. Note this means we won't get a balanced cluster,
just one that passes N+1 checks.
For algorithm details and usage, see the man page hn1(1). **Note**:
this program is deprecated, hbal should be used instead.
For algorithm details and usage, see the man page hn1(1).
.. note:: This program is deprecated, hbal should be used instead.
IAllocator plugin
-----------------
~~~~~~~~~~~~~~~~~
The ``hail`` iallocator plugin can be used for allocations of mirrored
and non-mirrored instances and for relocations of mirrored
instances. It needs to be installed in Ganeti's iallocator search
path—usually ``/usr/lib/ganeti/iallocators`` or
``/usr/local/lib/ganeti/iallocators``.
``/usr/local/lib/ganeti/iallocators``. See the man page hail(1).
Integration with Ganeti
-----------------------
......@@ -45,14 +52,14 @@ cluster or master node name. ``hail`` uses the standard iallocator API
and thus doesn't need any special setup (just needs to be installed in
the right directory).
For text files, a separate tool (hscan) is provided to automate their
gathering if RAPI is available, which is better since it can extract
more precise information. In case RAPI is not usable for whatever
reason, the following two commands should be run::
For generating the text files, a separate tool (hscan) is provided to
automate their gathering if RAPI is available, which is better since
it can extract more precise information. In case RAPI is not usable
for whatever reason, the following two commands should be run::
gnt-node list -oname,mtotal,mnode,mfree,dtotal,dfree,offline \
--separator '|' --no-headers > nodes
gnt-instance list -oname,admin_ram,sda_size,status,pnode,snodes \
gnt-instance list -oname,be/memory,sda_size,status,pnode,snodes \
--separator '|' --no-head > instances
These two files should be saved under the names of *nodes* and
......@@ -73,3 +80,7 @@ directory should be enough.
Internal (implementation) documentation is available in the ``apidoc``
directory.
.. Local Variables:
.. mode: rst
.. End:
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