Commit a392a6b8 authored by Michael Hanselmann's avatar Michael Hanselmann
Browse files

Add information about storage units framework



This updates the 2.1 design document with storage units framework information.
Signed-off-by: default avatarIustin Pop <iustin@google.com>
Signed-off-by: default avatarMichael Hanselmann <hansmi@google.com>
Reviewed-by: default avatarMichael Hanselmann <hansmi@google.com>
parent e337de97
......@@ -37,6 +37,49 @@ As for 2.0 we divide the 2.1 design into three areas:
Core changes
------------
Storage units modelling
~~~~~~~~~~~~~~~~~~~~~~~
Currently, Ganeti has a good model of the block devices for instances
(e.g. LVM logical volumes, files, DRBD devices, etc.) but none of the
storage pools that are providing the space for these front-end
devices. For example, there are hardcoded inter-node RPC calls for
volume group listing, file storage creation/deletion, etc.
The storage units framework will implement a generic handling for all
kinds of storage backends:
- LVM physical volumes
- LVM volume groups
- File-based storage directories
- any other future storage method
There will be a generic list of methods that each storage unit type
will provide, like:
- list of storage units of this type
- check status of the storage unit
Additionally, there will be specific methods for each method, for example:
- enable/disable allocations on a specific PV
- file storage directory creation/deletion
- VG consistency fixing
This will allow a much better modeling and unification of the various
RPC calls related to backend storage pool in the future. Ganeti 2.1 is
intended to add the basics of the framework, and not necessarilly move
all the curent VG/FileBased operations to it.
Note that while we model both LVM PVs and LVM VGs, the framework will
**not** model any relationship between the different types. In other
words, we don't model neither inheritances nor stacking, since this is
too complex for our needs. While a ``vgreduce`` operation on a LVM VG
could actually remove a PV from it, this will not be handled at the
framework level, but at individual operation level. The goal is that
this is a lightweight framework, for abstracting the different storage
operation, and not for modelling the storage hierarchy.
Feature changes
---------------
......
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