No Volumes No Shares - Superblock Issue?

[NigelBrownless]

ps the good news is that there seems to be data on the disk, I can see some file names (json)

That's encouraging.

[fvdw]

also no superblock in that file. I need to review my calcaluation...

[fvdw]

:scratch calculations are correct, lets read a bigger part of the file system, assuming there are bad sectors on the disk that are not accounted for in the xfs structure

Code: Select all

dd bs=4096 skip=121968964 count=256 if=/dev/md4 of=md4-backup1-256.img

Sorry to keep you busy
It could of course also be that info in the primary superblock is incorrect...then a workaround could be a scan of the whole array for superblocks.
But how important is the data for you on those disks?

[NigelBrownless]

Code: Select all

dd bs=406 skip=121968964 count=256 if=/dev/md4 of=md4-backup1-256.img

Gives the following ouput...

Code: Select all

256+0 records in
256+0 records out
1048576 bytes (1.0MB) copied, 0.281602 seconds, 3.6MB/s

File Attached.

[fvdw]

nope, no superblock :dry so I guess the info in primary superblock is wrong about AG size.
Now need to find a method to scan the whole disk to find super blocks :scratch

[fvdw]

I will write a script that will scan the array to find a backup superblock. Such a scan may take several hours as we will read block by block.
Not today because as I have some other jobs to do.
Again is the data on this array of importance for you? In other words is it worth the effort.

[NigelBrownless]

I will write a script that will scan the array to find a backup superblock. Such a scan may take several hours as we will read block by block.
Not today because as I have some other jobs to do.

Thanks for your help and time on this, much appreciated.

Again is the data on this array of importance for you? In other words is it worth the effort.

Yes, the data is important. There are some Photos on there that I would like to get back.

[fvdw]

attached a small script that could scan the array it search for a string "XFSB" as that is always at entry of a superblock.
It scan the partition with blocks of 1 MByte (smaller blocks will make scan very long).
If it detects the string in this block it will mention it and store output in a file superx.img (with x being the blocknr)
The program must be started with this command

Code: Select all

./scanmd /dev/md4 nrblocks

With nrblocks being the maximum number of blocks to be scanned,
Note: do not scan further then the size of the partition !
For example using 512000 as nrblocks will scan 500GB of the array.
As scanning takes time you may want to try this number, if it doesn't find a superblock you may enlarge it and scan again
Note: the filesystem may contain other files with this string, those will be listed as well
After the scan we will need to check content of the superX.img files to see if we have found a superblock

To install the program while you have the standalone kernel running on the nas.
Unpack the archive an put the program in the tftp folder of the fvdw-sl console
Start the tftp server in the console if not already running
copy the file and make uit executable
Note: replace ippc with the actual ip of your pc

Code: Select all

busybox tftp -r scanmd.sh -l /scanmd.sh -g ippc
chmod 755 /scanmd.sh

Example output on my pc

Code: Select all

root@fvdwsl-sg-pc:/direct-usb/public/ff # ./scanmd.sh /dev/sda8 256
10 MB scanned
20 MB scanned
30 MB scanned
40 MB scanned
50 MB scanned
60 MB scanned
70 MB scanned
80 MB scanned
90 MB scanned
100 MB scanned
block 108 file super108.img is not empty
110 MB scanned
120 MB scanned


[NigelBrownless]

Just a quick update.....The Scan is still ongoing.
I went with your suggestion of 512000.
So far we are at 3150 MB Scanned.
It doesn't appear to have found anything as yet, only at Block 1

Code: Select all

blocksize 1M block 1 file super1.img is not empty

[fvdw]

Thats correct that it found a superblock string in block 1 as that is the primary superblock.
And yes scanning in this way will take time.