Re: create metadata from DMRAID

On Tue, Jul 03, 2007 at 05:31:00PM +0200, Heinz Mauelshagen wrote:
> On Mon, Jul 02, 2007 at 04:51:24PM -0700, Fang, Ying wrote:
> > >
> > >The data structure already exist: raid_set and raid_dev.
> > >For one-level sets, a raid_set structure with multiple raid_dev
> > >structures hanging off.
> > >For 2-level sets (eg. RAID10), a top-level raid_set structure, multiple
> > >bottom level raid_set structures hanging off it and multiple raid_dev
> > >structures hanging off the bottom level ones.
> > >
> > >You got to check, if the properties (ie. the structure mebers) are
> > >sufficient or if we need to add some.
> > >
> > >> Then it calls .create of an
> > >> appropriate handler to build and write metadata to each hard device
> > of
> > >> the raid set.
> > >
> > >It calls a) .create and of that succeeds it'll call b) .write
> > >in a followup step.
> > 
> > You mean the metadata creation procedure is the reverse path of building
> > a raidset from metadata:
> > 1. create a raid set (struct raid_set) and its subsets
> > 2. create a list of raid devices for all subsets
> 
> Yes, a list of raid devices for each lowest level subset.
> 
> > 3. call .create for each raid device to generate a complete metadata
> > attached to the device (struct raid_dev)
> 
> Right, that's where we got to think about needing any additional
> members in structs raid_set and raid_dev in case we can't store 
> enough RAID set or RAID device properties.
> 
> > 4. call .write to write metadata to each hard drive.
> 
> Correct.
> 
> > 
> > 
> > >>
> > >> How about manual and auto rebuilding? Should updating metadata status
> > be
> > >> handled by DMRAID or device drivers?
> > >
> > >By dmraid using dmeventd, which is part of libdevmapper.
> > >You got to create a dmraid DSO for dmeventd to make that happen.
> > >Look at the mirror DSO for dmeventd for an example.
> > >
> > 
> > Is it to call dm_event_handler_create, and dm_event_registered_device to
> > create a dmraid DSO? I didn't find the mirror DSO. Could you give me the
> > name of the file? 
> 
> It is part of liblvm2:
> lib/mirror/mirror.c

s/mirror.c/mirrored.c/ :)

> 
> Heinz
> 
> > 
> > Thanks,
> > Ying