Re: Growing raid 5 to 6; /proc/mdstat reports a strange value?

On Fri, Jan 29, 2010 at 4:23 AM, Neil Brown [off-list ref] wrote:

On Sun, 24 Jan 2010 19:49:31 -0800
Michael Evans [off-list ref] wrote:

quoted

mdX : active raid5 sdd1[8](S) sdb1[7](S) sdf8[0] sdl8[4] sdk2[5]
sdc1[6] sdj6[3] sdi8[1]
     Y blocks super 1.1 level 5, 128k chunk, algorithm 2 [6/6] [UUUUUU]

# mdadm --grow /dev/mdX --level=6 --raid-devices=8
--backup-file=/root/mdX.backupfile

mdX : active raid6 sdd1[8] sdb1[7] sdf8[0] sdl8[4] sdk2[5] sdc1[6]
sdj6[3] sdi8[1]
     Y blocks super 1.1 level 6, 128k chunk, algorithm 18 [8/9] [UUUUUU_U]
     [>....................]  reshape =  0.0% (33920/484971520)
finish=952.6min speed=8480K/sec

!!! mdadm 3.1.1 I wanted an 8 device raid-6;  Why do you show 9?

That is weird isn't it.  It is showing that 8 devices are in the array, of
which 9 are working.  That cannot be right.
More worrying is that the second last device claim to not be present, which
doesn't seem right.

quoted

What is it showing me now???

blocks super 1.1 level 6, 128k chunk, algorithm 2 [8/10] [UUUUUUUU]

So now of the 8 devices, 10 are working!!  At least all are present.

quoted

... Did it actually do what I want but just show me the wrong result
with kernel 2.6.32-gentoo-r2

Some simple testing suggests it did do what you want, but reported something
silly in /proc/mdstat.

I'll see if I can work out what is happening.

Thanks for the report.

NeilBrown

As a follow-up:
* Looking at the device via mdadm --detail /dev/mdX (while still
invalid in /proc/mdstat) showed the correct information.
* When I stopped and re-started the array the information in
/proc/mdstat was valid.
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html