Bug#728677: mdadm: has no superblock - assembly aborted (but it has)

[Marc Lehmann]

On Fri, Dec 05, 2014 at 01:23:19PM +0300, Michael Tokarev <mjt at tls.msk.ru> wrote:
> I'm not sure what to make out of this bugreport really.  Tagging with
> `moreinfo' for now.

Not sure what more info I could deliver, it seems to be clear from the
bugreport as-is. However, the volume is long gone, so I now have the same
information as you.

> What I notice however is that ata-HGST_HDS724040ALE640_2 contains a
> partition table, and mdadm correctly detects this.  So this is a first
> data device in the array, and actual data starts there.  With superblock
> format v. 1.0, this is also the start of the drive, ie, the same partition
> table exists on this drive and on your array.  This is a sure way of
> making problems, since the system first see your ata drive and tries to
> parse partition table in there, and might even try to mount some partitions,
> making the drive busy, so mdadm is unable to open it for assembly.

Nothing in my system will randomly mount partitions it hasn't explicitly
been asked to mount.

In any case, if this were true,. it's simply a bug in mdadm - mdadm should
not say "there is no superblock" when there really is a superblock but
something simply kept it from opening the device.

> When you create raid5 array, use superblock version 1.1 or 1.2 (1.2 is
> the default), so no other tools will try to access your component devices
> outside the array.

You seem to be confused about the idea behind this bug report: the idea was
to report an actual bug in the tool, I didn't try to abuse the bug tracker to
get support. I don't have an actual problem with mdadm, I simply reported
that mdadm gives a erong error message.

> With this context I'd say it is an operator error.

Again, I think you misunderstood - I was reporting a bug, not asking for
support. It might or might not be true that, what I did is not the optimal
way, or the way it should be done, or the state-of-the-art-technique to do
things, but that is completely irrelevant, as this report is about a wrong
message in mdadm.

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