Synnefo » snf-ganeti » ganeti-local

Ganeti Cluster tools (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.

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

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.

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``.

Integration with Ganeti

-----------------------

The ``hbal`` and ``hn1`` programs can either get their input from text

files, or online from a cluster via RAPI. For online collection via

RAPI, the "-m" argument to both hn1 and hbal should specify the

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::

    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 \

      --separator '|' --no-head > instances

These two files should be saved under the names of *nodes* and

*instances*.

Installation

------------

If installing from source, you need a working ghc compiler (6.8 at

least) and some extra Haskell libraries which usually need to be

installed manually:

- json

- curl

Once these are available, just typing *make* in the top-level

directory should be enough.

Internal (implementation) documentation is available in the ``apidoc``

directory.