[SATLUG] 1st question - RAID5 quit - Next examinations

Samuel Leon satlug at net153.net
Fri Aug 21 09:37:20 CDT 2009


David Labens wrote:
> From: Don Wright <satlug at sbcglobal.net>
> Date: Monday, August 17, 2009, 1:40 PM
> 
> Please post the results of 
> "mdadm --examine /dev/sda1 /dev/sdb1 /dev/sde1" for us to chew on.  --Don
> 
> Here's what I did:  
> root at RCH-SERVER:/proc# mdadm --examine /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sde1
> 
> & here are the results:
> 
> /dev/sda1:
>           Magic : a92b4efc
>         Version : 1.0
>     Feature Map : 0x1
>      Array UUID : 13782a18:85c82f51:e999ccd0:c2ca0614
>            Name : 0
>   Creation Time : Sat Jan 10 13:03:52 2009
>      Raid Level : raid5
>    Raid Devices : 4
> 
>  Avail Dev Size : 488391728 (232.88 GiB 250.06 GB)
>      Array Size : 1465175040 (698.65 GiB 750.17 GB)
>   Used Dev Size : 488391680 (232.88 GiB 250.06 GB)
>    Super Offset : 488391984 sectors
>           State : clean
>     Device UUID : 7cd2101b:57561ce9:d9ba5317:d46c59d3
> 
> Internal Bitmap : -234 sectors from superblock
>     Update Time : Sat Aug  8 20:24:05 2009
>        Checksum : d16f35eb - correct
>          Events : 2986
> 
>          Layout : left-asymmetric
>      Chunk Size : 128K
> 
>     Array Slot : 1 (0, 1, failed, failed, failed)
>    Array State : uU__ 3 failed
> /dev/sdb1:
>           Magic : a92b4efc
>         Version : 1.0
>     Feature Map : 0x1
>      Array UUID : 13782a18:85c82f51:e999ccd0:c2ca0614
>            Name : 0
>   Creation Time : Sat Jan 10 13:03:52 2009
>      Raid Level : raid5
>    Raid Devices : 4
> 
>  Avail Dev Size : 488391728 (232.88 GiB 250.06 GB)
>      Array Size : 1465175040 (698.65 GiB 750.17 GB)
>   Used Dev Size : 488391680 (232.88 GiB 250.06 GB)
>    Super Offset : 488391984 sectors
>           State : active
>     Device UUID : f333bc44:36324c45:d6c6face:b0cb6f6f
> 
> Internal Bitmap : -234 sectors from superblock
>     Update Time : Wed Jul 29 22:59:24 2009
>        Checksum : aaf8c83a - correct
>          Events : 89
> 
>          Layout : left-asymmetric
>      Chunk Size : 128K
> 
>     Array Slot : 2 (0, 1, 2, failed, 3)
>    Array State : uuUu 1 failed
> /dev/sdc1:
>           Magic : a92b4efc
>         Version : 1.0
>     Feature Map : 0x1
>      Array UUID : 13782a18:85c82f51:e999ccd0:c2ca0614
>            Name : 0
>   Creation Time : Sat Jan 10 13:03:52 2009
>      Raid Level : raid5
>    Raid Devices : 4
> 
>  Avail Dev Size : 488391728 (232.88 GiB 250.06 GB)
>      Array Size : 1465175040 (698.65 GiB 750.17 GB)
>   Used Dev Size : 488391680 (232.88 GiB 250.06 GB)
>    Super Offset : 488391984 sectors
>           State : clean
>     Device UUID : 16caaeab:d141a887:5e8aa2c7:9f856976
> 
> Internal Bitmap : -234 sectors from superblock
>     Update Time : Sat Aug  8 19:02:59 2009
>        Checksum : 53f6ee4e - correct
>          Events : 2978
> 
>          Layout : left-asymmetric
>      Chunk Size : 128K
> 
>     Array Slot : 4 (0, 1, failed, failed, 3)
>    Array State : uu_U 2 failed
> /dev/sde1:
>           Magic : a92b4efc
>         Version : 1.0
>     Feature Map : 0x1
>      Array UUID : 13782a18:85c82f51:e999ccd0:c2ca0614
>            Name : 0
>   Creation Time : Sat Jan 10 13:03:52 2009
>      Raid Level : raid5
>    Raid Devices : 4
> 
>  Avail Dev Size : 488391728 (232.88 GiB 250.06 GB)
>      Array Size : 1465175040 (698.65 GiB 750.17 GB)
>   Used Dev Size : 488391680 (232.88 GiB 250.06 GB)
>    Super Offset : 488391984 sectors
>           State : clean
>     Device UUID : 6fc091a8:2805559a:b799e126:192b56ed
> 
> Internal Bitmap : -234 sectors from superblock
>     Update Time : Sat Aug  8 20:24:05 2009
>        Checksum : 39b36fd2 - correct
>          Events : 2986
> 
>          Layout : left-asymmetric
>      Chunk Size : 128K
> 
>     Array Slot : 0 (0, 1, failed, failed, failed)
>    Array State : Uu__ 3 failed
> 
> Thanks,
> David Labens
> San Antonio, TX
> 


 From http://linux-raid.osdl.org/index.php/Reconstruction
"Look at the sylog produced by trying to start the array, you'll see the 
event count for each superblock; usually it's best to leave out the disk 
with the lowest event count, i.e the oldest one."

So if  I am reading that right then one can tell the age of the drive 
from the events count? We see here that in this array all counts are 
over 2900 except sdb which is only 89.  What that tells me is that sdb 
was failed and removed from the array many months ago (possibly from an 
improper shut down/ powerloss).  If sdb is that old then the data on it 
will be horribly out of sync.  This leaves us with only sda,sdc, and sde 
  to reassemble the array with.  sdc as we know is on it's way out.  So 
we must get the data off of it and onto a fresh drive!

Sam


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