[openstack-dev] [Ironic] RAID interface - backing disk hints

Jim Rollenhagen jim at jimrollenhagen.com
Tue Jan 20 14:36:41 UTC 2015

On Tue, Jan 20, 2015 at 07:28:46PM +0530, Ramakrishnan G wrote:
> Hi All,
> This is regarding the RAID configuration spec that was posted for review
> some time back:
> https://review.openstack.org/#/c/135899/
> This review consists of a generic RAID interface currently proposed jointly
> by Redhat (for DRAC hardware) and HP (for iLO hardware).   This spec
> defines a common interface for doing RAID configuration which can be used
> for both drivers for now, and may be followed by any driver later on who
> wishes to implement RAID configuration.
> In the changes proposed in the spec, the driver should be able to figure
> out the disks to be used for creating RAID on the machine, when some hints
> are given by the operator to Ironic.  The hints help Ironic to figure out
> what disks should be used for creating RAID.  Initially we started with a
> few (namely disk type (ssd vs hdd) and interface type (scsi vs sata vs
> ...), etc.  But later on due to request from some other folks to include
> some more criterias (namely filter disks based on inputs on model, firmware
> version, vendor due to various reasons), we added it to the list of hints.
> Now, we have
> * some set of folks *who don't want *model, firmware version, vendor as
> criteria because if they are added, every driver would need to implement
> them.
> * some set of folks *who want *model, firmware version, vendor as criteria
> because there are practical use-cases in an environment.
> We have confirmed that filtering based on model, firmware version and
> vendor can be done on both HP and DRAC hardware for now.
> I would like to hear everyone's thoughts and probably reach a conclusion of
> whether be open to include more criteria or not.

I think these filters make sense. An operator may want to say "RAID all
disks of this model"; that's completely reasonable.

We've already decided we want to implement the same filters for deciding
which disk to put the root on[0], and so we'll need to write this code
for most/all drivers anyway. We can simply re-use this code for the RAID
use case.

// jim

[0] http://specs.openstack.org/openstack/ironic-specs/specs/kilo/root-device-hints.html

> Please pour in your thoughts on the thread
> Regards,
> Ramakrishnan (irc: rameshg87)

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