Re: SES Enclosure Management.

[NeilBrown <neilb@suse.de>]

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On Tue, 14 Feb 2012 13:46:32 -0700 Robert Woodworth
<robertjwoodworth@gmail.com> wrote:

> On 02/14/2012 01:31 PM, NeilBrown wrote:
> > On Tue, 14 Feb 2012 10:30:37 -0700 Robert Woodworth
> > <robertjwoodworth@gmail.com>  wrote:
> >
> >> Has anyone ever thought of integrating SES managed enclosures into the
> >> kernel RAID system?  I briefly looked through the archives and have
> >> not found anything on the topic.
> >>
> >> Some HW based RAID controllers do this flawlessly now, there is no
> >> reason why the kernel RAID cannot also.  (LSI MegaRAID)
> >>
> >> 1) When a drive is part if a managed enclosure, the RAID system should
> >> address it by location instead of by enumerated device node.  The SES
> >> device in the enclosure can map the physical slot to a physical drive.
> >>   The RAID admin (mdamd) should be able to add/fail/identify devices
> >> based on slot.
> > Does this just mean that the admin should using names in /dev/disk/by-path/
> > rather than /dev/sdXX to address devices?  What can md or mdadm do to help?
> I don't like the /by-path/ too well, it is not human readable.  I would 
> propose that the SES module that is already in the base kernel be 
> expanded to provide a /dev/disk/by-location/<enclosureID>/<slot> -> 
> /dev/sdXY

It isn't the kernel that provides these links, it is udev.
If there is some tool that can extract the enclosureID and slot values, then
one or 2 lines in a udev 'rules' file should be able to create the links.

> >
> The one piece that could be included in the kernel level is the display 
> of /proc/mdstat to show the enclosureID and slot number

I'm finding /proc/mdstat increasingly distasteful.  It is very convenient but
hard to extend usefully.
I' rather create something like
   mdadm --status

which reported the status of all (or some) arrays with similar usability to
/proc/mdstat, but more room to extend it.


Thanks,
NeilBrown


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