On Mon, Nov 17, 2014 at 11:29 AM, 'Aaron Karper' via ganeti-devel <[email protected]> wrote: > For many users the change from uniform disk templates would make their > lifes more difficult. Therefore we want to be externally compatible as > far as possible. > > Signed-off-by: Aaron Karper <[email protected]> > --- > doc/design-disks.rst | 26 ++++++++++++++++++++++++++ > 1 file changed, 26 insertions(+) > > diff --git a/doc/design-disks.rst b/doc/design-disks.rst > index 18fb75c..b5d0fab 100644 > --- a/doc/design-disks.rst > +++ b/doc/design-disks.rst > @@ -169,6 +169,32 @@ with the instance's disk objects. So in the backend we > will only have to > replace the ``disks`` slot with ``disks_info``. > > > +Supporting the old interface > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > + > +The current interface is designed with a uniform disk type in mind and > +this interface should still be supported to not break tools and > +workflows downstream. > + > +The behaviour is fully compatible for instances with constantly > +attached, uniform disks. > + > +Whenever an operation operates on an instance, the operation will only > +consider the disks attached. If the operation is specific to a disk > +type, it will only consider disks with that type and ignore the rest > +(but throw an error as before if no disk of that type is attached).
I'm not entirely sure about this. If the operation is specific to a disk type, should it operate only on disks of that type, or should it operate on the instance only if all the disks attached to that instance are of the given type, and error out otherwise? Which approch would be less surprising to the user? > + > +When setting the disk template of an instance, we convert all currently > +attached disks to that template. This means that all disk types > +currently attached must be convertible to the new template. > + > +Since the disk template as a configuration value is going away, it needs > +to be replaced for queries. If the instance has no disks, the > +disk_template will be 'diskless', if it has disks of a single type, its > +disk_template will be that type, and if it has disks of multiple types, > +the new disk template 'mixed' will be returned. > + > + > Eliminating the disk template from the instance > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > -- > 2.1.0.rc2.206.gedb03e5 > Thanks, Michele -- Google Germany GmbH Dienerstr. 12 80331 München Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg Geschäftsführer: Graham Law, Christine Elizabeth Flores
