Re: equal size not large enough for RAID1?

["Lars Täuber" <taeuber@bbaw.de>]

Hi Neil,

Neil Brown <neilb@suse.de> schrieb:
> On Wednesday March 5, taeuber@bbaw.de wrote:
> > Hallo list,
> 
> Hi.
> 
> > 
> > monosan# cat /proc/partitions:
> >    9     4 12697912448 md4
> >    9     9 12697912312 md9
> >  152  5632 12697912448 etherd/e22.0
> > 
> > 
> > monosan:~ # cat /proc/mdstat 
> > Personalities : [raid1] [raid0] [raid6] [raid5] [raid4] 
> > md9 : active raid1 md4[0]
> >       12697912312 blocks super 1.0 [2/1] [U_]
> >       
> > md4 : active raid6 dm-0[0] dm-8[14] dm-7[13] dm-6[12] dm-5[11] dm-4[10] dm-3[9] dm-2[8] dm-14[7] dm-13[6] dm-12[5] dm-11[4] dm-10[3] dm-9[2] dm-1[1]
> >       12697912448 blocks level 6, 64k chunk, algorithm 2 [15/15] [UUUUUUUUUUUUUUU]
> > 
> > 
> > 
> > But then this:
> > monosan:~ # mdadm /dev/md9 -a /dev/etherd/e22.0 
> > mdadm: /dev/etherd/e22.0 not large enough to join array
> 
> This would be because mdadm is reserving a bit of space in case you
> want to add an internal bitmap one day.  And the version of mdadm you
> are now using is reserving more space than the version that was used
> to create the array does.

we are using SuSE 10.3 here. And I don't remember if mdadm was updated due to an online update. But I think it should be consistent/compatible with the version shipped in the original distribution.

What is this internal bitmap good for? Is there a documentation somewhere on the net about this?


> 
> I should fix that...
> 
> If you want a quick fix and are happy to compile your own mdadm, then
> edit super1.c and remove the line
> 
> 	devsize -= choose_bm_space(devsize);
> 
> in avail_size1().

I could compile, but on our productive server we don't compile anything that is shipped with the distribution due to the possibility to have security updates from SuSE.

I just repeated the following:

monosan:~ # mdadm -C /dev/md9 -l1 -n2 -x0 /dev/md4 /dev/etherd/e22.0 
mdadm: Defaulting to verion 1.0 metadata
mdadm: /dev/md4 appears to be part of a raid array:
    level=raid1 devices=2 ctime=Thu Mar  6 09:39:37 2008
mdadm: /dev/etherd/e22.0 appears to be part of a raid array:
    level=raid1 devices=2 ctime=Thu Mar  6 09:39:37 2008
Continue creating array? y
mdadm: array /dev/md9 started.

monosan:~ # mdadm -V
mdadm - v2.6.2 - 21st May 2007

monosan:~ # mdadm /dev/md9 -f /dev/etherd/e22.0 
mdadm: set /dev/etherd/e22.0 faulty in /dev/md9

monosan:~ # mdadm /dev/md9 -r /dev/etherd/e22.0 
mdadm: hot removed /dev/etherd/e22.0

monosan:~ # mdadm /dev/md9 -a /dev/etherd/e22.0 
mdadm: /dev/etherd/e22.0 not large enough to join array

monosan:~ # cat /etc/SuSE-release 
openSUSE 10.3 (X86-64)
VERSION = 10.3

How come?

Thanks
Lars
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