Re: MD RAID Bug 7/15/12

[NeilBrown <neilb@suse.de>]

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On Mon, 1 Oct 2012 18:51:09 -0700 Mark Munoz <mark.munoz@rightthisminute.com>
wrote:

> Neil,
> 
> Thank you again so much for taking time out of your day to personally help me it really means a lot.  I have ran the command and have successfully recreated my md1  Now however md2 will not assemble.  I get this error.
> 
> sudo mdadm --assemble --force /dev/md2 /dev/md0 /dev/md1
> mdadm: superblock on /dev/md1 doesn't match others - assembly aborted
> 
> Would I be correct in thinking that I just need to recreate md2 now as well?

Maybe, but probably not.
I would think it more likely that md1 wasn't created quite right - otherwise
it should have the right metadata.

What does:
  mdadm -E /dev/md1
display now?  How does that compare with "mdadm -E /dev/md0" ?

What about
   mdadm -E /dev/sdaf
(or any other device in md1)?  How does that compare to what was displayed
previously?

NeilBrown


> 
> I assume with this command?
> 
> sudo mdadm --create --assume-clean /dev/md2 --level=0 --chunk=64 --metadata=1.2 --raid-devices=2 /dev/md0 /dev/md1
> 
> Mark Munoz
> 
> On Oct 1, 2012, at 2:00 PM, Mark Munoz <mark.munoz@rightthisminute.com> wrote:
> > 
> >> On Sat, 29 Sep 2012 17:12:40 -0700 Mark Munoz
> >> <mark.munoz@rightthisminute.com> wrote:
> >> 
> >>> Hi I appear to have been affected by the bug you found on 7/15/12.  The data I have on this array is really important and I want to make sure I get this correct before I actually make changes.
> >>> 
> >>> Configuration:
> >>> md0 is a RAID 6 volume with 24 devices and 1 spare.  It is working fine and was unaffected.
> >>> md1 is a RAID 6 volume with 19 devices and 1 spare.  It was affected.  All the drives show as unknown raid level and 0 devices.  With the exception of device 5.  It has all the information.
> >>> 
> >>> Here is the output from that drive:
> >>> 
> >>> serveradmin@hulk:/etc/mdadm$ sudo mdadm --examine /dev/sdaf
> >>> /dev/sdaf:
> >>>         Magic : a92b4efc
> >>>       Version : 1.2
> >>>   Feature Map : 0x0
> >>>    Array UUID : 6afb3306:144cec30:1b2d1a19:3a56f0d3
> >>>          Name : hulk:1  (local to host hulk)
> >>> Creation Time : Wed Aug 15 16:25:30 2012
> >>>    Raid Level : raid6
> >>>  Raid Devices : 19
> >>> 
> >>> Avail Dev Size : 5860531120 (2794.52 GiB 3000.59 GB)
> >>>    Array Size : 99629024416 (47506.82 GiB 51010.06 GB)
> >>> Used Dev Size : 5860530848 (2794.52 GiB 3000.59 GB)
> >>>   Data Offset : 2048 sectors
> >>>  Super Offset : 8 sectors
> >>>         State : clean
> >>>   Device UUID : 205dfd9f:9be2b9ca:1f775974:fb1b742c
> >>> 
> >>>   Update Time : Sat Sep 29 12:22:51 2012
> >>>      Checksum : 9f164d8e - correct
> >>>        Events : 38
> >>> 
> >>>        Layout : left-symmetric
> >>>    Chunk Size : 4K
> >>> 
> >>>  Device Role : Active device 5
> >>>  Array State : AAAAAAAAAAAAAAAAAAA ('A' == active, '.' == missing)
> >>> 
> >>> Now I also have md2 which is a striped RAID of both md0 and md1.
> >>> 
> >>> When I type:
> >>> 
> >>> sudo mdadm --create --assume-clean /dev/md1 --level=6 --chunk=4 --metadata=1.2 --raid-devices=19 /dev/sdaa /dev/sdab /dev/sdac /dev/sdad /dev/sdae /dev/sdaf /dev/sdag /dev/sdah /dev/sdai /dev/sdaj /dev/sdak /dev/sdal /dev/sdam /dev/sdan /dev/sdao /dev/sdap /dev/sdaq /dev/sdar /dev/sdas
> >>> 
> >>> the following error for each device.
> >>> 
> >>> mdadm: /dev/sdaa appears to be part of a raid array:
> >>>   level=-unknown- devices=0 ctime=Wed Aug 15 16:25:30 2012
> >>> mdadm: partition table exists on /dev/sdaa but will be lost or
> >>>      meaningless after creating array
> >>> 
> >>> I want to make sure by running this above command that I won't affect any of the data of md2 when I assemble that array after creating md1.  Any help on this issue would be greatly appreciated.  I would normally just DD copies but as you can see I would have to buy 19 more 3TB hard drives as well as the time to DD each drive.  It is a production server and that kind of down time would really rather be avoided.  
> >> 
> >> Running this command will only overwrite the 4K of metadata, 4K from the
> >> start of the devices.  It will not write anything else to any device.
> >> 
> >> so yes, it is safe.
> >> 
> >> NeilBrown
> >> 
> >> 
> >> 
> >>> 
> >>> Thank you so much for your time.
> >>> 
> >>> Mark Munoz
> >>> 623.523.3201--
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> >> 
> > 
> 
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