Leon Woestenberg wrote:
Hello all,

On 9/13/06, Tejun Heo <[EMAIL PROTECTED]> wrote:
Ric Wheeler wrote:
> Leon Woestenberg wrote:
>> In short, I use ext3 over /dev/md0 over 4 SATA drives /dev/sd[a-d]
>> each driven by libata ahci. I unplug then replug the drive that is
>> rebuilding in RAID-5.
>>
>> When I unplug a drive, /dev/sda is removed, hotplug seems to work to
>> the point where proc/mdstat shows the drive failed, but not removed.

Yeap, that sounds about right.

>> Every other notion of the drive (in kernel and udev /dev namespace)
>> seems to be gone after unplugging. I cannot manually removed the drive
>> using mdadm, because it tells me the drive does not exist.

I see.  That's a problem.  Can you use /dev/.static/dev/sda instead?  If
you can't find those static nodes, just create one w/ 'mknod
my-static-sda b 8 0' and use it.


I did further testing of the ideas set out in this thread.

Although I can use (1) static device nodes, or (2) persistent naming
with the proper udev rules, each has its own kind of problems with md.

As long as the kernel announces drives as disappeared but md still
holds a lock, replugging drives will map to other major:minor number
no matter what I try in userspace.

Static device nodes will therefore not help me select the drive that
was unplugged/plugged per se.

Persistent naming using udev works OK (I used /dev/bay0 through
/dev/bay3 to pinpoint the drive bays) but these disappear upon
unplugging, while md keeps a lock to the major:minor, so replugging
will move it to different major:minor numbers.

So the question remains: How will hotplug and md work together?

How does md and hotplug work together for current hotplug devices?

I have the same questions.

How does this work in a pure SCSI environment? (has it been tested?)
If something should change, should those changes be in the MD layer?
Or can this *really* all be done nicely from userspace?  How?

I've got to fix some problems related to this, for a couple of clients,
and would like to Do It Right, or as close to Right as reality permits.

Cheers
--
Mark Lord
Real-Time Remedies Inc.
[EMAIL PROTECTED]

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