Question about a mismatch between documentation and how mdadm currently works.

[Kevin O'Gorman]

It seems to be something else: I was having so much going wrong that I was
really confused and not connecting dots properly.

I/O errors were causing the arrays to be degraded or dropped.  When
re-assembled using the
instructions I had, they were assigned the identities I mentioned.  Now
that I seem to have the
I/O errors under control (it was a power distribution problem), things are
matching the
documentation more closely.

Sorry for the alarm.  I seem to be in the steep part of at least one
learning curve.

On Mon, Apr 3, 2017 at 12:51 PM, Tom H <tomh0665 at gmail.com> wrote:

> On Sat, Apr 1, 2017 at 9:50 PM, Kevin O'Gorman <kogorman at gmail.com> wrote:
> >
> > I'm fooling around with RAID on Linux for the first time. Lots to
> > learn. I have one issue that keeps coming up with creating RAID arrays
> > with mdadm.
> >
> > The documentation I have all says to create arrays with something like
> > mdadm --create /dev/md0 (and some more stuff) and what follows really
> > does indicate they expect the array to appear as /dev/md0. What
> > happens when I try it is that the array is created as /dev/md127. If I
> > create two arrays, the next one is /dev/md126.
> >
> > Likewise, if I assemble a RAID array, they go to the high numbers no
> > matter what my command-line says.
> >
> > What's up with this? Is it historical? Is something just ignoring that
> > part of the command line? Is that part even required?
>
> # mdadm --create /dev/md0 -l 1 -n 2 /dev/sdb /dev/sdc
> # cat /proc/mdstat
> Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
> [raid4] [raid10]
> md0 : active raid1 sdc[1] sdb[0]
>  1047552 blocks super 1.2 [2/2] [UU]
> #
>
> A random shot in the dark: is your hostname set properly?
>
> Or, more usefully, does running "examine" output your actual hostname.
> So for my array above, mdadm -E /dev/sd{b,c}
>
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-- 
Kevin O'Gorman
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