On 02/14/2012 01:31 PM, NeilBrown wrote:
On Tue, 14 Feb 2012 10:30:37 -0700 Robert Woodworth
<robertjwoodworth@xxxxxxxxx> 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
If you have ever worked with AIX, all devices have physical locations in
the configurations held by the kernel.
2) If the RAID system fails a drive, it should notify the SES
management and turn on the fail bit and the fail LED.
"mdadm --monitor" will run a script on drive failure. This could easily
notify the SES management.
So maybe all we need here is a script to plug in to mdadm... Would you like
to write one?
Yes, I thought of that too.
3) The RAID system should be able to turn on the 'identify' bit and
LEDs for an array or a single drive.
Again, it sounds like you just need a script to ask mdadm which devices are
included in a given array, and then do whatever magic is needed to turn on
the light.
It is fairly easy to extra the device list from the output of
mdadm --detail --brief --verbose /dev/md/whatever
but it might be good to make it easier to extra from
mdadm --detail --export /dev/md/whatever
Would you like to write such a script?
Yes, I could take that on.
I'm currently doing firmware on a managed enclosure. Although my
vendor only supports LSI MegaRAID, there is no reason why my
enclosures cannot work in the same manner on a kernel RAID system.
Request for comments...
It sounds to me like you just need a few scripts to provide some
enclosure-specific functionality. I would be happy to include them in the
mdadm distribution.
Or maybe there is something that I didn't understand??
Thanks,
NeilBrown
The one piece that could be included in the kernel level is the display
of /proc/mdstat to show the enclosureID and slot number
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