Re: RAIDframe: passing component capabilities

[Greg Oster <oster%netbsd.org@localhost>]

On Fri, 31 Mar 2017 17:15:38 +0200
Edgar Fuß <ef%math.uni-bonn.de@localhost> wrote:

> > given that RAIDframe (nor ccd, nor much else) has a general 'query
> > the underlying layers to ask about this capability' function.  
> Is there a ``neither'' missing between ``that'' and ``RAIDframe''?

Yes, sorry.

> > (NetBSD 8 refusing to configure a RAID set because of this is not an
> > option.)  
> Of course not. With my model, you would need to (re-)configure the
> RAID set with ``all components have SCSI tagged queueing'' in order
> for the RAID device to announce that capability. If one of the drives
> is SATA, that configuration fails. If you later try to replace a SCSI
> drive with a SATA one it fails like it fails when the replacement
> drive has insufficient capacity.
> It's just like with capacities: There's no need to announce the full
> component capacity to the set (well, in fact, you don't use the full
> drive capacity for the partition that constitutes the component), but
> the component needs to have at least the announced capacity (in fact,
> you need to be able to create a partition of sufficient size on the
> drive). With capabilities, there would also be no need to announce
> all the drive's capabilities, but a component (original or
> replacement) needs to have at least the announced capabilities.

That still requires RAIDframe then asking the components (or having
them report to RAIDframe when they are attached) about whether or not
they can do a certain thing, in order to decide whether or not the
reconfiguration succeeds or fails.

Later...

Greg Oster