Synnefo » snf-ganeti

- :doc:`design-shared-storage` (Updated to reflect the new ExtStorage

  Interface)

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Ganeti shared storage support

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2.3 storage model. It also documents the ExtStorage Interface.

EXAMPLES

--------

In the following examples we assume that you have already installed

successfully two ExtStorage providers: ``pvdr1`` and ``pvdr2``

Add a new instance with a 10G first disk provided by ``pvdr1`` and a 20G

second disk provided by ``pvdr2``::

    # gnt-instance add -t ext --disk=0:size=10G,provider=pvdr1

                              --disk=1:size=20G,provider=pvdr2

Add a new instance with a 5G first disk provided by provider ``pvdr1``

and also pass the ``prm1``, ``prm2`` parameters to the provider, with

the corresponding values ``val1``, ``val2``::

   # gnt-instance add -t ext

                      --disk=0:size=5G,provider=pvdr1,prm1=val1,prm2=val2

Modify an existing instance of disk type ``ext`` by adding a new 30G

disk provided by provider ``pvdr2``::

   # gnt-instance modify --disk 1:add,size=30G,provider=pvdr2 <instance>

Modify an existing instance of disk type ``ext`` by adding 2 new disks,

of different providers, passing one parameter for the first one::

   # gnt-instance modify --disk 2:add,size=3G,provider=pvdr1,prm1=val1

                         --disk 3:add,size=5G,provider=pvdr2

                         <instance>

|  \| {size=*VAL*,provider=*PROVIDER*}[,param=*value*... ][,mode=*ro\|rw*]

the default of read-write). The size is interpreted (when no unit is

given) in mebibytes. You can also use one of the suffixes *m*, *g* or

*t* to specify the exact the units used; these suffixes map to

mebibytes, gibibytes and tebibytes. For LVM and DRBD devices, the LVM

volume group can also be specified (via the ``vg`` key). For DRBD

devices, a different VG can be specified for the metadata device using

the ``metavg`` key. For ExtStorage devices, also the ``provider``

option is mandatory, to specify which ExtStorage provider to use.

When creating ExtStorage disks, also arbitrary parameters can be passed,

to the ExtStorage provider. Those parameters are passed as additional

comma separated options. Therefore, an ExtStorage disk provided by

provider ``pvdr1`` with parameters ``param1``, ``param2`` would be

passed as ``--disk 0:size=10G,provider=pvdr1,param1=val1,param2=val2``.

The minimum information needed to specify an ExtStorage disk are the

``size`` and the ``provider``. For example:

``--disk 0:size=20G,provider=pvdr1``.

sharedfile

    Disk devices will be regulare files on a shared directory.

blockdev

    Disk devices will be adopted pre-existent block devices.

ext

    Disk devices will be provided by external shared storage,

    through the ExtStorage Interface using ExtStorage providers.

    # gnt-instance add -t rbd --disk 0:size=30g -B maxmem=512 -o debian-etch \

      -n node1.example.com instance1.example.com

    # gnt-instance add -t ext --disk 0:size=30g,provider=pvdr1 -B maxmem=512 \

      -o debian-etch -n node1.example.com instance1.example.com

    # gnt-instance add -t ext --disk 0:size=30g,provider=pvdr1,param1=val1 \

      --disk 1:size=40g,provider=pvdr2,param2=val2,param3=val3 -B maxmem=512 \

      -o debian-etch -n node1.example.com instance1.example.com

| [\--disk add:size=*SIZE*[,vg=*VG*][,metavg=*VG*] \|

|  \--disk add:size=*SIZE*,provider=*PROVIDER*[,param=*value*... ] \|

|  \--disk [*N*:]remove \|

optional ``vg=``*VG* option specifies an LVM volume group other than the

default volume group to create the disk on. For DRBD disks, the

device. When adding an ExtStorage disk the ``provider=``*PROVIDER*

option is also mandatory and specifies the ExtStorage provider. Also,

for ExtStorage disks arbitrary parameters can be passed as additional

comma separated options, same as in the **add** command. ``--disk``

*N*``:add,size=``**SIZE** can be used to add a disk at a specific index.

The ``--disk remove`` option will remove the last disk of the instance.

Use ``--disk `` *N*``:remove`` to remove a disk by its index. The

``--disk`` *N*``:mode=``*MODE* option will change the mode of the Nth

disk of the instance between read-only (``ro``) and read-write (``rw``).

plain, drbd, file, sharedfile, rbd or ext disk template. For the ext

template to work, the ExtStorage provider should also support growing.

This means having a ``grow`` script that actually grows the volume of

the external shared storage.

primary). This works for instances with drbd template (in which case you

can only fail to the secondary node) and for externally mirrored

templates (sharedfile, blockdev, rbd and ext) (in which case you can

fail to any other node).

If the instance's disk template is of type sharedfile, blockdev, rbd or

ext, then you can explicitly specify the target node (which can be any

node) using the ``-n`` or ``--target-node`` option, or specify an

iallocator plugin using the ``-I`` or ``--iallocator`` option. If you

omit both, the default iallocator will be used to specify the target

node.

If the instance's disk template is of type drbd, the target node is

automatically selected as the drbd's secondary node. Changing the

secondary node is possible with a replace-disks operation.

For externally mirrored templates also ``-n`` is available::

    # gnt-instance failover -n node3.example.com instance1.example.com

As with failover, it works for instances having the drbd disk template

or an externally mirrored disk template type such as sharedfile,

blockdev, rbd or ext.

If the instance's disk template is of type sharedfile, blockdev, rbd or

ext, then you can explicitly specify the target node (which can be any

node) using the ``-n`` or ``--target-node`` option, or specify an

iallocator plugin using the ``-I`` or ``--iallocator`` option. If you

omit both, the default iallocator will be used to specify the target

node.  Alternatively, the default iallocator can be requested by

specifying ``.`` as the name of the plugin.

If the instance's disk template is of type drbd, the target node is

automatically selected as the drbd's secondary node. Changing the

secondary node is possible with a replace-disks operation.

The migration command needs a perfectly healthy instance for drbd

instances, as we rely on the dual-master capability of drbd8 and the

disks of the instance are not allowed to be degraded.

migration to attempting recovery from a failed previous migration. In

Move will move the instance to an arbitrary node in the cluster. This