--- On Wed, 13/4/11, John Robinson <john.robinson@anonymous.org.uk> wrote:

From: John Robinson <redacted>
Subject: Re: RAID6 data-check took almost 2 hours, clicking sounds, system unresponsive
To: "NeilBrown" <redacted>
Cc: "Gavin Flower" <redacted>, linux-raid@vger.kernel.org
Date: Wednesday, 13 April, 2011, 23:58
On 13/04/2011 12:13, NeilBrown
wrote:

quoted

On Wed, 13 Apr 2011 11:57:24 +0100 John Robinson
[off-list ref] 

wrote:

quoted

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On 12/04/2011 22:30, Gavin Flower wrote:

[...]

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md0 : active raid6 sda3[0] sdb3[4] sdd3[3]

sdc3[5](F) sde3[1]

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        10751808

blocks level 6, 64k chunk, algorithm 2 [5/4] [UU_UU]

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This one I don't get:
md0 : active raid6 sda3[0] sde3[1] sdd3[3] sdb3[4]

sdc3[5](F)

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which ought to be UUUU_ again...

Perhaps `mdadm -D /dev/md[0-2]` would make things

clearer...

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This is actually more horrible than you imagine.

It isn't really, I was asking for the mdadm -D output
precisely to get the list of role and slot numbers, having
noticed there was no slot 2 in Gavin's setup...

[...]

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As the current number is pretty much useless, I should

probably change it to

quoted

the slot number, or an arbitrarily assigned larger

number for spares.

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This would be an incompatible change, but I very much

doubt anyone uses the

quoted

numbers for what they actually are, so I doubt that

would really matter.

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It has just never really got high on my list of

priorities....

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Lesson:  Ignore the number in [] - it doesn't

mean anything useful.

It's not useless, it reflects the order in which devices
were added to the array.

Suggestion: Don't change the number in /proc/mdstat, just
sort the devices by role (i.e. the same order as the UUUU_)
instead of device node, and show spares at the end (as per
your arbitrarily-assigned larger number, which this way you
never have to display).

Cheers,

John.

The first time I saw this kind of thing: I was very worried, thinking I had 2 bad drives - until I looked more closely, a few hours later.  I am sure I am not the only to initially react that way.

From a user perspective, I think that the list of drives and the [UUUU_] string, should be ordered in the alphanumeric order of the logical drive names. Also modify the '[...]' string to indicate spares (not having spares, not sure what it does now).

e.g.
/dev/sda  /dev/sdb /dev/sdc[F} /dev/sdd /dev/sde[S} /dev/sdf.
would be reflected by:
[aaFaSa]

Not sure what the 'U' stood for. Marking actives disks with 'a' seems to make more sense to me.  The upper and lower case would make it easier to see what is active and what is not.  Similarly, the RAID entries would be better, from a user perspective, to be sorted on name.

There are probably lots of technical reasons this can't be done, but users don't care! :-)  We just want it to look pretty, be easy to understand, and not be scary.

Just my 2 pennies worth...

When I put my developer hat on, I tend to feel that users rate looking pretty' and 'not be scary' as being more important than 'be easy to understand' - or perhaps, I am too cynical


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