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

John Pappas j at jvpappas.net
Sat Sep 12 10:43:55 CDT 2009


Quick and useful output for SW RAID systems: `cat /proc/mdstat` (notice run
as normal user)  shows rebuild status and involved disks quickly.
mine:~> cat /proc/mdstatPersonalities : [raid1] [raid0] [raid6] [raid5]
[raid4] [linear]
md126 : active raid1 sdc1[0] sdd1[1]
      136448 blocks [2/2] [UU]

md127 : active raid5 sdg1[0] sde1[4] sdf1[3] sdb1[2] sda1[1]
      1953535744 blocks level 5, 64k chunk, algorithm 2 [5/5] [UUUUU]

md1 : active raid1 sdc3[0] sdd3[1]
      290904896 blocks [2/2] [UU]

md3 : active raid1 sdd2[0] sdc2[1]
      2008000 blocks [2/2] [UU]

unused devices: <none>

Can't explain the name change for the md12[67] from md[02] respectively, but
it happened after I rebuilt the system.
HTH,
jp

On Fri, Sep 11, 2009 at 17:24, David Labens <adlabens at swbell.net> wrote:

> 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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