Thanks again. I have visited those pages (twice no less) and nothing seems to be new from the concepts (both raid and lvm) since I last studied them.
My problem is that I'm not familiar enough with the recovery tools and the common practical pitfalls to do this comfortably without the hand holding of this mailing list :)
Here is the requested output:
Note: Since I have 3-4 other arrays running (root device etc.) which don't have anything to do with this one and are all working fine...I am just putting the output of the relevant devices (in order to avoid confusing everybody). Please let me know if you still require the full output.
mdadm -Dvvs /dev/md_d127
mdadm: md device /dev/md_d127 does not appear to be active.
mdadm --assemble /dev/md_d127 /dev/sda1 /dev/sdb5 /dev/sdc5 /dev/sdd5
mdadm: /dev/md_d127 assembled from 2 drives and 1 spare - not enough to start the array.
Says that the device /dev/md_d127 is not active (because its not active in /proc/mdstat)
mdadm -Evvs /dev/sda1 /dev/sdb5 /dev/sdc5 /dev/sdd5
/dev/sda1:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x1
Array UUID : 42c56ea0:2484f566:387adc6c:b3f6a014
Name : GATEWAY:127 (local to host GATEWAY)
Creation Time : Sat Aug 22 09:44:21 2009
Raid Level : raid5
Raid Devices : 4
Avail Dev Size : 586099060 (279.47 GiB 300.08 GB)
Array Size : 1758296832 (838.42 GiB 900.25 GB)
Used Dev Size : 586098944 (279.47 GiB 300.08 GB)
Data Offset : 272 sectors
Super Offset : 8 sectors
State : clean
Device UUID : 571fa32b:d76198a1:0f5d3a2d:31f6d6b8
Internal Bitmap : 2 sectors from superblock
Update Time : Fri Mar 19 00:56:15 2010
Checksum : 7e769165 - expected aa523227
Events : 3796145
Layout : left-symmetric
Chunk Size : 64K
Device Role : spare
Array State : .AA. ('A' == active, '.' == missing)
/dev/sdb5:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x1
Array UUID : 42c56ea0:2484f566:387adc6c:b3f6a014
Name : GATEWAY:127 (local to host GATEWAY)
Creation Time : Sat Aug 22 09:44:21 2009
Raid Level : raid5
Raid Devices : 4
Avail Dev Size : 586099060 (279.47 GiB 300.08 GB)
Array Size : 1758296832 (838.42 GiB 900.25 GB)
Used Dev Size : 586098944 (279.47 GiB 300.08 GB)
Data Offset : 272 sectors
Super Offset : 8 sectors
State : clean
Device UUID : f8ebb9f8:b447f894:d8b0b59f:ca8e98eb
Internal Bitmap : 2 sectors from superblock
Update Time : Fri Mar 19 00:56:15 2010
Checksum : 1005cfbc - correct
Events : 3796145
Layout : left-symmetric
Chunk Size : 64K
Device Role : Active device 2
Array State : .AA. ('A' == active, '.' == missing)
/dev/sdc5:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x1
Array UUID : 42c56ea0:2484f566:387adc6c:b3f6a014
Name : GATEWAY:127 (local to host GATEWAY)
Creation Time : Sat Aug 22 09:44:21 2009
Raid Level : raid5
Raid Devices : 4
Avail Dev Size : 586099060 (279.47 GiB 300.08 GB)
Array Size : 1758296832 (838.42 GiB 900.25 GB)
Used Dev Size : 586098944 (279.47 GiB 300.08 GB)
Data Offset : 272 sectors
Super Offset : 8 sectors
State : clean
Device UUID : d9ce99fc:79bc1e9d:197d5b11:c990e007
Internal Bitmap : 2 sectors from superblock
Update Time : Fri Mar 19 00:56:15 2010
Checksum : a9f9f59f - correct
Events : 3796145
Layout : left-symmetric
Chunk Size : 64K
Device Role : Active device 1
Array State : .AA. ('A' == active, '.' == missing)
/dev/sdd5:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x1
Array UUID : 42c56ea0:2484f566:387adc6c:b3f6a014
Name : GATEWAY:127 (local to host GATEWAY)
Creation Time : Sat Aug 22 09:44:21 2009
Raid Level : raid5
Raid Devices : 4
Avail Dev Size : 586099060 (279.47 GiB 300.08 GB)
Array Size : 1758296832 (838.42 GiB 900.25 GB)
Used Dev Size : 586098944 (279.47 GiB 300.08 GB)
Data Offset : 272 sectors
Super Offset : 8 sectors
State : clean
Device UUID : 763a832f:1a9a7ea8:ce90d4a3:32e8ae54
Internal Bitmap : 2 sectors from superblock
Update Time : Fri Mar 19 00:56:15 2010
Checksum : c78aab46 - correct
Events : 3796145
Layout : left-symmetric
Chunk Size : 64K
Device Role : spare
Array State : .AA. ('A' == active, '.' == missing)
Regards,
Anshuman
On 26-Mar-2010, at 9:08 AM, Michael Evans wrote:
> On Thu, Mar 25, 2010 at 7:09 AM, Anshuman Aggarwal
> <anshuman@xxxxxxxxxxxxx> wrote:
>> Thanks Michael, I am clear about the problem of why the multiple failure would cause me to lose data. Which is why I wanted to consult this mailing list before proceeding.
>>
>> Could you tell me how to keep the array read-only? and mark one or both of these spares as active forcibly? and Also, once I am able to use these spares as active and the data is not consistent in a particular stripe, how does the kernel resolve the inconsistency (as in what data does it use, the one based on the data stripes or the one based on the parity?) this one is just academic interest since it'll be difficult to figure out which is the right data anyways.
>>
>> Thanks,
>> Anshuman
>>
>
> Please, read the wikipedia page first,
>
> http://en.wikipedia.org/wiki/RAID
>
> and then this
>
> http://wiki.tldp.org/LVM-on-RAID (some links need updating, but it's
> still up to date for concepts)
>
>
> With that background nearly out of the way, please stop, and read them
> both again. Yes, seriously. In order to prevent data loss you'll
> need to have a good understanding of what RAID does, so that you can
> watch out for ways it can fail.
>
> The next step, before we do /anything/ else is for you to post the
> COMPLETE output of these commands.
>
> mdadm -Dvvs
> mdadm -Evvs
>
> They will help everyone on the list better understand the state of the
> metadata records and what potential solutions might be possible.
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