[SATLUG] 1st question - RAID5 quit - Questions

David Labens adlabens at swbell.net
Fri Aug 21 19:10:52 CDT 2009


First, the setup:

All the drives are the same age, purchased at the same time, installed simultaneously, and brought online together.  The event counts, however, show:

/sda1 = 2986
/sdb1 = 89
/sdc1 = 2978
/sde1 = 2986

This APPEARS to mean that /sdb1 failed a long time ago, and the data will probably be WAY out of sync.  However, /sdb1 passed all the tests of the SmartMonTools.  So, I think the data may be bad but the drive itself may be good.  I think this MAY have happened due to a cable coming loose?  But, I'm not sure.

/sdc1 has the read errors and we know this one must be replaced.  I think that the ddrescue program may be the best way to duplicate the drive data onto the new drive that I have.  SpinRite is also available, but at a cost of about $90, I'd prefer to try ddrescue first.

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

Second, my line of thinking:

I think I need to physically remove /sdb1 because it's probably got data that's old and is out of sync from the other 3 drives.

Then, I think I need to install the new blank drive (I'll call it /sdf or /sdf1 in this email for clarification purposes).

Then, I need to ddrescue the data from /sdb1 to /sdf1

Then, I SHOULD be able to reassemble the array and have access to the data.

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

Now my questions:

Is this the right process to be trying?

Do I need to do anything to remove /sdb1 other than simply unplugging it (assuming that it's not mounted)?

To make /sdf1 work, I'll need to physically connect it, and then run:
    sfdisk -d /dev/sda | sfdisk --force /dev/sdf
which should copy the partition info from /sda (one of the apparently still-good drives) to the new drive.  

BUT, should I do that from one of the still-good drives, or should I do it from the drive that's bad?

Once I do have the partition info on the new /sdf, then using ddrescue would seem fairly straight forward.

Then, should I remove /sdc, and try to get the data to re-sync with just the 3 drives connected? - I am ignorant of the commands to get the data to re-sync, so I'm pretty apprehensive about it.

I know I'm forgetting something, some really important questions that I need to ask, so any other hints & tips will be appreciated.

Thanks,
David Labens
San Antonio, TX


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



> 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
> 



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