[SATLUG] RAID5 Recovery - Post Mortem Review - Food For Thought

David Labens adlabens at swbell.net
Fri Sep 11 17:24:31 CDT 2009


I've now copied all the data off the RAID5 array - using the copy as a
backup till I get backups up.  The 1 tb drive has approximately 244 gb
of data on it (used space), and I've copied ALL the data from the array.

The array consists of 4 HDDs with 250 GB each, a total array size of approx 1 TB, but approx 750 GB of usable storage space.

My
"off the top" conclusion is that the array should have approximately
500 GB of free space on it.  But, I'm finding that the numbers don't
add up.  Note the "Used Dev Size :
488391680 (465.77 GiB 500.11 GB)"  And I wonder what that means?

-----------------------------------




root at RCH-SERVER:/# mdadm --detail /dev/md0

   

/dev/md0:

        Version :
01.00

  Creation Time : Sat
Jan 10 13:03:52 2009

     Raid Level :
raid5

     Array Size :
732587520 (698.65 GiB 750.17 GB)

  Used Dev Size :
488391680 (465.77 GiB 500.11 GB)

   Raid Devices : 4

  Total Devices : 4

Preferred Minor : 0

    Persistence :
Superblock is persistent

   

  Intent Bitmap :
Internal

   

    Update Time : Sat
Aug 29 06:35:14 2009

          State :
active

 Active Devices : 4

Working Devices : 4

 Failed Devices : 0

  Spare Devices : 0

   

         Layout :
left-asymmetric

     Chunk Size : 128K

   

           Name : 0

           UUID :
13782a18:85c82f51:e999ccd0:c2ca0614

         Events : 3006

   

    Number   Major  
Minor    RaidDevice State 

       0       8      
65        0      active sync   /dev/sde1

       1       8       
1        1      active sync   /dev/sda1

       2       8      
17        2      active sync   /dev/sdb1

       4       8      
33        3      active sync   /dev/sdc1

   

-----------------------------------

BUT,
all four disks seem to be working:

-----------------------------------




root at RCH-SERVER:/# mdadm --examine /dev/sda1 (same stats for sdb1, sdc1, & sde1. sdd1 is the 80 gb OS HDD):


   

/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 29 06:35:14 2009

       Checksum :
d1882345 - correct

         Events : 3006

   

         Layout :
left-asymmetric

     Chunk Size : 128K

   

    Array Slot : 1 (0,
1, 2, failed, 3)

    Array State 
: uUuu 1 failed

   

root at RCH-SERVER:/#

  -----------------------------------
Also, this may help with the analysis:
-----------------------------------




root at RCH-SERVER:/# fdisk -l 


   

Disk /dev/sda: 250.0 GB, 250059350016 bytes

255 heads, 63 sectors/track, 30401 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Disk identifier: 0x41413535

   

   Device Boot      Start         End      Blocks  
Id  System

/dev/sda1              
1       30401   244196001  
fd  Linux raid autodetect/dev/sdb1              
1       30401   244196001  
fd  Linux raid autodetect

 /dev/sdc1               1      
30401   244196001   fd 
Linux raid autodetect

 
/dev/sde1              
1       30401   244196001  
fd  Linux raid autodetect  

root at RCH-SERVER:/#

David Labens

San Antonio, TX


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