+rasputin who wanted to add some more suggestions. On Wed, Feb 3, 2016 at 3:28 PM, Dimitris Aragiorgis <[email protected]> wrote:
> Hi, > > Is there any reason for not having this one merged yet? > > Thanks, > dimara > > * 'Lisa Velden' via ganeti-devel <[email protected]> > [2016-01-22 15:53:21 +0100]: > > > This design document introduces the gnt-disk command, so that disks can > > be treated as top-level entities. > > > > Signed-off-by: Lisa Velden <[email protected]> > > --- > > Makefile.am | 3 +- > > doc/design-draft.rst | 1 + > > doc/design-standalone-disks.rst | 161 > ++++++++++++++++++++++++++++++++++++++++ > > 3 files changed, 164 insertions(+), 1 deletion(-) > > create mode 100644 doc/design-standalone-disks.rst > > > > diff --git a/Makefile.am b/Makefile.am > > index 0080f00..f93aac6 100644 > > --- a/Makefile.am > > +++ b/Makefile.am > > @@ -546,7 +546,7 @@ hypervisor_hv_kvm_PYTHON = \ > > > > jqueue_PYTHON = \ > > lib/jqueue/__init__.py \ > > - lib/jqueue/exec.py \ > > + lib/jqueue/exec.py \ > > lib/jqueue/post_hooks_exec.py > > > > storage_PYTHON = \ > > @@ -733,6 +733,7 @@ docinput = \ > > doc/design-shared-storage.rst \ > > doc/design-shared-storage-redundancy.rst \ > > doc/design-ssh-ports.rst \ > > + doc/design-standalone-disks.rst \ > > doc/design-storagetypes.rst \ > > doc/design-sync-rate-throttling.rst \ > > doc/design-systemd.rst \ > > diff --git a/doc/design-draft.rst b/doc/design-draft.rst > > index e4c9f85..18d9ca9 100644 > > --- a/doc/design-draft.rst > > +++ b/doc/design-draft.rst > > @@ -28,6 +28,7 @@ Design document drafts > > design-global-hooks.rst > > design-scsi-kvm.rst > > design-disks.rst > > + design-standalone-disks.rst > > > > .. vim: set textwidth=72 : > > .. Local Variables: > > diff --git a/doc/design-standalone-disks.rst > b/doc/design-standalone-disks.rst > > new file mode 100644 > > index 0000000..37b68ee > > --- /dev/null > > +++ b/doc/design-standalone-disks.rst > > @@ -0,0 +1,161 @@ > > +========================= > > +Disks as Separate Objects > > +========================= > > + > > +.. contents:: :depth: 3 > > + > > +This design document improves the former :doc:`design-disks` document. > > +It introduces the gnt-disk command, so that disks can really be treated > > +as top-level entities. However, the focus is on disks as separate > objects, > > +that is, we do not introduce other new features, such as instances with > > +mixed disk templates. > > + > > + > > +Current state and shortcomings > > +============================== > > + > > +What can already be done? > > +------------------------- > > + > > +Currently, disks can only be created within an instance. But it is > > +already possible to have disks reside in the configuration without being > > +tied to an instance if that disk was previously detached from an > > +instance with a modification command like > > +``gnt-instance modify --disk *UUID*:detach *INSTANCE*``. > > + > > +However, detaching a disk from an instance results in a warning in > > +``gnt-cluster verify`` about orphan volumes for most of the disk > > +templates. > > + > > +Besides detaching, it is also possible to attach a pre-existing disk to > > +an instance and to adopt disks into the Ganeti configuration which have > > +been created outside of Ganeti, e.g. on plain KVM with LVM. Currently, > > +disk adoption is done with ``gnt-instance add --disk=*N*:adopt=*LV*``, > > +which means it is adopt and attach in one step. > > + > > +It is possible to list all disks on a node with their associated > > +instances, if any. The command for that is ``gnt-node volumes``. > However, > > +only LVM volumes are listed with that command. > > + > > +Furthermore, instances can be destroyed while its disks are left as is. > > +But therefore disks have to be detached first and > > +``gnt-instance remove`` has to be called afterwards. > > + > > +What cannot be done at the current state? > > +----------------------------------------- > > + > > +Standalone disks cannot be properly accessed. There is no command that > > +lists all disks for all disk templates, nor is it easy to find the > > +respective instance, if any, for a given disk. > > + > > +It is also not convenient that detached disks can only be removed when > > +they are attached to an instance again and that disk adoption only works > > +for lvm volumes and block devices at the current state. > > + > > +Currently, disk adoption only works with plain and blockdev disk > > +templates. It should also work with the ext disk template, so that in a > > +shared storage environment we can do cross-cluster failovers, where we > > +instantaneously move an instance from one cluster to another. > > + > > +Proposed changes > > +================ > > + > > +As the current way to do disk adoption as well as removing detached > > +disks from the Ganeti configuration is not intuitive, we propose to > > +introduce a new command ``gnt-disk`` that supports the following > > +subcommands: > > + > > +* ``gnt-disk info *DISK_UUID|DISK_NAME*``: all relevant information for > > + a disk is listed, e.g. size, connected instance, position among other > > + disks > > + > > +* ``gnt-disk list``: disks that should be listed can be specified with > > + ``--attached``, ``--detached`` or ``--all`` where all disks are also > > + shown as default if no option was given > > + > > +* ``gnt-disk adopt *VOLUME*``: adopts a volume into the Ganeti > > + configuration. This should work not only for plain and block devices, > > + but also for shared storage. > > + > > +* ``gnt-disk create --disk-template *DT* --size *VAL* options``: creates > > + a disk, so that it appears in the Ganeti configuration. This command > > + will take the same options as ``gnt-instance add --disk`` except for > > + the position value and the adopt option. > > + > > +* ``gnt-disk modify *DISK_UUID|DISK_NAME* options``: changes the options > > + of the disk. Available options are > > + > > + + ``mode``: The access mode, i.e. either ``ro`` (read-only) or the > > + default ``rw`` (read-write). > > + + ``name``: This option specifies a name for the disk that can be > > + used as an identifier. > > + > > +* ``gnt-disk abandon *DISK_UUID|DISK_NAME*``: removes the given disk > from > > + the Ganeti configuration without destroying the disk. With an > > + additional option ``--remove-data`` the disk will also be destroyed. > > + > > +* ``gnt-disk snapshot [--target-disk-name *NAME*] > > + *SRC_DISK_UUID|SRC_DISK_NAME*``: creates a snapshot of the given > source > > + disk. This will be a new disk with the specified name and read-only > > + access mode > > + > > +* ``gnt-disk clone [--target-disk-name *NAME*] > > + *SRC_DISK_UUID|SRC_DISK_NAME*``: creates a new disk with read-write > > + access mode and optionally with a given disk name > > + > > +* ``gnt-disk convert --target-disk-template *DT* > *DISK_UUID|DISK_NAME*``: > > + converts the disk template of a disk into the new disk template > > + > > +* ``gnt-disk copy [--target-disk-name *NAME*] --target-disk-template > *DT* > > + *SRC_DISK_UUID|SRC_DISK_NAME*``: creates a new disk that is identical > > + to the source disk, but has a different disk template > > + > > +Besides the ``gnt-disk`` command, we propose the following changes: > > + > > +* Make the storage path information retrieved from the logical id from > > + disks also available through the basic instance information from the > > + RAPI > > + > > +* Disallow all disk operations via the RAPI, except for moves > > + > > +* Add a flag to preserve disks to the ``gnt-instance remove`` command > > + > > +Further possible changes > > +======================== > > + > > +If there is need for it, it would be also possible to move disk > > +detachment and attachment to the new ``gnt-disk`` command, so that we > > +would have the following simplified commands, instead of the respective > > +``gnt-instance modify --disk`` commands: > > + > > +* ``gnt-disk attach [--position *N*] {--uuid *DISK_UUID* | --name > > + *DISK_NAME*} *INSTANCE*``: attaches a disk to an instance. If the disk > > + was not in the configuration before, an error is raised. If no > position > > + argument was provided, the disk will be attached at the last index of > > + the instance's disks. > > + > > +* ``gnt-disk detach {--uuid *DISK_UUID* | --name *DISK_NAME* | > --position > > + *N*} *INSTANCE*``: detaches a disk from an instance and leaves it in > > + the Ganeti configuration > > + > > +Note that this does not add new functionality, because it will behave > > +just as the current solution for disk attachment and detachment. For > > +example, disk attachment might still fail due to misaligned DRBD disks. > > + > > +Implementation details > > +====================== > > + > > +Especially for the ``gnt-disk create`` part it will be handy to > re-factor > > +the current ``LUInstanceCreate`` in such a way that we can reuse the > disk > > +creation part. That can be achieved with tasklets like they are used > > +in ``LUInstanceMigrate`` and ``LUInstanceReplaceDisks``. The same holds > > +for ``LUInstanceSetParams``, because we want to be able to make disk > > +changes also to standalone disks. > > + > > +Except for creating diskless instances on purpose, the diskless disk > > +template should not be required if an instance becomes diskless, but the > > +instance should be considered to be in the state ``diskless``. > > + > > +The logic for adoption should be moved down to ``lib/storage/bdev.py``, > > +so that it becomes uniform to all disk templates and it is, thus, easy > to > > +extend it for external storage. > > -- > > 2.7.0.rc3.207.g0ac5344 > -- Lisa Velden Software Engineer [email protected] Google Germany GmbH Erika-Mann-Straße 33 80636 München Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
