1 ganeti-extstorage-interface(7) Ganeti | Version @GANETI_VERSION@
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7 ganeti-extstorage-interface - Specifications for ExtStorage providers
12 The method for supporting external shared storage in Ganeti is to have
13 an ExtStorage provider for each external shared storage hardware type.
14 The ExtStorage provider is a set of files (executable scripts and text
15 files), contained inside a directory which is named after the provider.
16 This directory must be present across all nodes of a nodegroup (Ganeti
17 doesn't replicate it), in order for the provider to be usable by Ganeti
18 for this nodegroup (valid). The external shared storage hardware should
19 also be accessible by all nodes of this nodegroup too.
24 There are seven required files: *create*, *attach*, *detach*, *remove*,
25 *grow*, *verify* (executables) and *parameters.list* (text file).
30 All commands will get their input via environment variables. A common
31 set of variables will be exported for all commands, and some of them
32 might have extra ones. Note that all counts are zero-based.
34 Since Ganeti version 2.5, the environment will be cleaned up before
35 being passed to scripts, therefore they will not inherit the environment
36 in with which the ganeti node daemon was started. If you depend on any
37 environment variables (non-Ganeti), then you will need to define or
38 source them appropriately.
41 The name of the volume. This is unique for Ganeti and it uses it
42 to refer to a specific volume inside the external storage. Its
43 format is ``UUID.ext.diskX`` where ``UUID`` is produced by Ganeti
44 and is unique inside the Ganeti context. ``X`` is the number of the
48 The volume's size in mebibytes.
51 Available only to the **grow** script. It declares the new size of
52 the volume after grow (in mebibytes). To find the amount of grow,
53 the scipt should calculate the number VOL_NEW_SIZE - VOL_SIZE.
56 Each ExtStorage parameter (see below) will be exported in its own
57 variable, prefixed with ``EXTP_``, and upper-cased. For example, a
58 ``fromsnap`` parameter will be exported as ``EXTP_FROMSNAP``.
67 The **create** command is used for creating a new volume inside the
68 external storage. The ``VOL_NAME`` denotes the volume's name, which
69 should be unique. After creation, Ganeti will refer to this volume by
70 this name for all other actions.
72 Ganeti produces this name dynamically and ensures its uniqueness inside
73 the Ganeti context. Therefore, you should make sure not to provision
74 manually additional volumes inside the external storage with this type
75 of name, because this will lead to conflicts and possible loss of data.
77 The ``VOL_SIZE`` variable denotes the size of the new volume to be
80 If the script ends successfully, a new volume of size ``VOL_SIZE``
81 should exist inside the external storage. e.g:: a lun inside a NAS
84 The script returns ``0`` on success.
89 This command is used in order to make an already created volume visible
90 to the physical node which will host the instance. This is done by
91 mapping the already provisioned volume to a block device inside the host
94 The ``VOL_NAME`` variable denotes the volume to be mapped.
96 After successful attachment the script returns to its stdout a string,
97 which is the full path of the block device to which the volume is
98 mapped. e.g:: /dev/dummy1
100 When attach returns, this path should be a valid block device on the
103 The attach script should be idempotent if the volume is already mapped.
104 If the requested volume is already mapped, then the script should just
105 return to its stdout the path which is already mapped to.
110 This command is used in order to unmap an already mapped volume from the
111 host node. Detach undoes everything attach did. This is done by
112 unmapping the requested volume from the block device it is mapped to.
114 The ``VOL_NAME`` variable denotes the volume to be unmapped.
116 ``detach`` doesn't affect the volume itself. It just unmaps it from the
117 host node. The volume continues to exist inside the external storage.
118 It's just not accessible by the node anymore. This script doesn't return
119 anything to its stdout.
121 The detach script should be idempotent if the volume is already
122 unmapped. If the volume is not mapped, the script doesn't perform any
125 The script returns ``0`` on success.
130 This command is used to remove an existing volume from the external
131 storage. The volume is permanently removed from inside the external
132 storage along with all its data.
134 The ``VOL_NAME`` variable denotes the volume to be removed.
136 The script returns ``0`` on success.
141 This command is used to grow an existing volume of the external storage.
143 The ``VOL_NAME`` variable denotes the volume to grow.
145 The ``VOL_SIZE`` variable denotes the current volume's size (in
146 mebibytes). The ``VOL_NEW_SIZE`` variable denotes the final size after
147 the volume has been grown (in mebibytes).
149 The amount of grow can be easily calculated by the scipt and is:
151 grow_amount = VOL_NEW_SIZE - VOL_SIZE (in mebibytes)
153 Ganeti ensures that: ``VOL_NEW_SIZE`` > ``VOL_SIZE``
155 If the script returns successfully, then the volume inside the external
156 storage will have a new size of ``VOL_NEW_SIZE``. This isn't immediately
157 reflected to the instance's disk. See ``gnt-instance grow`` for more
158 details on when the running instance becomes aware of its grown disk.
160 The script returns ``0`` on success.
165 The *verify* script is used to verify consistency of the external
166 parameters (ext-params) (see below). The command should take one or more
167 arguments denoting what checks should be performed, and return a proper
168 exit code depending on whether the validation failed or succeeded.
170 Currently, the script is not invoked by Ganeti, but should be present
171 for future use and consistency with gnt-os-interface's verify script.
173 The script should return ``0`` on success.
182 This file declares the parameters supported by the ExtStorage provider,
183 one parameter per line, with name and description (space and/or tab
184 separated). For example::
186 fromsnap Snapshot name to create the volume from
187 nas_ip The IP of the NAS appliance
189 The parameters can then be used during instance add as follows::
191 # gnt-instance add --disk=0:fromsnap="file_name",nas_ip="1.2.3.4" ...
196 Backwards compatibility
197 ~~~~~~~~~~~~~~~~~~~~~~~
199 The ExtStorage Interface was introduced in Ganeti 2.6.
200 Ganeti 2.6 and up is compatible with the ExtStorage Interface.
205 All the scripts should display an usage message when called with a wrong
206 number of arguments or when the first argument is ``-h`` or ``--help``.
208 .. vim: set textwidth=72 :