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Re: mdadm and UUIDs for its component drives



On Sun, Jun 26, 2011 at 2:25 PM, Andrew McGlashan
<andrew.mcglashan@affinityvision.com.au> wrote:

> Anyway.... the long and short of it is, I can use mdadm without regard to
> what devices are found, such as /dev/sda /dev/sdb /dev/sdc and the like as I
> rely purely on the UUID functionality, which as you know, mdadm handles
> perfectly well.  ;-)

 :)

 ...mmmm you see, this is the bit that has me concerned.  /dev/mdN can
be referred to by its unique UUID, but that's *not* what i'm referring
to.  and, from what you're saying, you appear to be implying that yes,
the external drives can pop up as /dev/sda through /dev/sdc and be
"confused" - and thus it is pure luck (or actually design) that the
drives *happen* to all be part of the same identical RAID-1 mirroring
array.

 so i realise martin that you've already answered, but it would be
really good if you could explicitly confirm:

 yes, mdadm names its RAID drives by UUID (as can clearly be seen in
/dev/mdadm/mdadm.conf) but does it *also* refer to its *COMPONENT*
drives (internally, and non-obviously, and undocumentedly) by UUID and
then report to the outside world that it's using whatever name
(/dev/sdX) which can, under these external-drives scenario, change.

 l.


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