Re: All spares in Raid 5, default chunk? version of mdadm significant?

Hi all,
 Hate to bump a thread but have I missed any information that would help to get me help :)? 

Neil, 
 as far as the default chunk sizes and mdadm versions are concerned, I am guessing you may be amongst the few who would know that conclusively? Also could the data offset and super offset be significant?

Thanks,
Anshu

On 22-Jun-2012, at 5:50 PM, Anshuman Aggarwal wrote:

Hi,
 I have a 6 device raid 5 array which had 1 disk go bad and then due to a power outage, the machine shutdown and when it started all the disks were showing up as spares with the following mdadm -E output (sample for one given below and full for all devices attached).

This md device was part a Physical Volume for a LVM Volume Group. 

I am trying to recreate the array using mdadm --create --assume-clean using 1 device as missing. I am checking if the device is getting created correctly by checking the UUID of the created device which would match if the device gets created correctly.

I have tried a few combinations of the disk order that I believe is right however I think I'm getting tripped up by the fact that the mdadm I used to create this md device was some 2.x series and now we are on 3.x (and I may have taken some of the defaults originally which I don't' remember)
What all 'defaults' have changed over the versions so I can try those? Like chunk size? Can we manually configure the super/data offset? Are those significant when we do an mdadm --create --assume-clean?

Thanks,
Anshu

/dev/sda5:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x0
     Array UUID : b480fe0c:c9e29256:0fcf1b0c:1f8c762c
           Name : GATEWAY:RAID5_500G
  Creation Time : Wed Apr 28 16:10:43 2010
     Raid Level : -unknown-
   Raid Devices : 0

 Avail Dev Size : 976768002 (465.76 GiB 500.11 GB)
  Used Dev Size : 976765954 (465.76 GiB 500.10 GB)
    Data Offset : 2048 sectors
   Super Offset : 8 sectors
          State : active
    Device UUID : a8499a91:628ddde8:1cc8f4b9:749136f9

    Update Time : Sat May 19 23:04:23 2012
       Checksum : 9950883c - correct
         Events : 1


   Device Role : spare
   Array State :  ('A' == active, '.' == missing)

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