DSM-G600, DNS-3xx and NSA-220 Hack Forum

Being hunted with the prospect of incorrectly created file system on the DNS-323 especially when using the Seagate 1TB 702.11 hard drives and the consequent loss of the data I have decided to resort back to the old trusty linux PC and a command line to verify what is going on. And indeed I found discrepancy in disk partition size.

The two disks from D-link enclosure are mounted as /dev/sda and /dev/sdb on the PC.

The inconsistency shows up in fdisk:
# fdisk /dev/sdb

The number of cylinders for this disk is set to 121601.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)

Command (m for help): p

Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1          66      530113+  82  Linux swap / Solaris
/dev/sdb2             131      121404   974133405   83  Linux
/dev/sdb4              67         130      514080   83  Linux

Partition table entries are not in disk order

Note, that the /dev/sdb2 ends at cylinder 121404 while the disk has 121601 cylinders. So there are 198 cylinders wasted or approximately 1.6 GBytes.

Since we have an exact copy of sda on sdb I am going to delete partition sda2 and create it again this time using the full disk capacity.

#fdisk /dev/sda

Command (m for help): d
Partition number (1-4): 2

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 2
First cylinder (131-121601, default 131):
Using default value 131
Last cylinder or +size or +sizeM or +sizeK (131-121601, default 121601):
Using default value 121601

Command (m for help): p

Disk /dev/sda: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1          66      530113+  82  Linux swap / Solaris
/dev/sda2             131      121601   975715807+  83  Linux
/dev/sda4              67         130      514080   83  Linux

Partition table entries are not in disk order

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

Interestingly the type of the file system is remembered between deleting and creating the partition.

Next I will create two raid arrays, one with the properly sized disk and another one with the old disk as md0 and md1 respectively.

mdadm --create --verbose /dev/md0 --level 1 --raid-devices=2 missing /dev/sda2
mdadm: /dev/sda2 appears to contain an ext2fs file system
    size=974133312K  mtime=Sat Feb 23 00:32:10 2008
mdadm: size set to 975715712K
Continue creating array? y
mdadm: array /dev/md0 started.

mdadm --create --verbose /dev/md1 --level 1 --raid-devices=2 missing /dev/sdb2
mdadm: /dev/sdb2 appears to contain an ext2fs file system
    size=974133312K  mtime=Sat Feb 23 00:32:10 2008
mdadm: /dev/sdb2 appears to be part of a raid array:
    level=raid1 devices=2 ctime=Sat Jul 12 12:15:45 2008
mdadm: size set to 974133312K
Continue creating array? y
mdadm: array /dev/md1 started.

Note the difference in size is showing already.

Then I will clean format  /dev/md0, which will become the data transfer target.

# mke2fs -v -m 0 /dev/md0
mke2fs 1.40.4 (31-Dec-2007)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
121978880 inodes, 243928928 blocks
0 blocks (0.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=0
7445 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
        4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
        102400000, 214990848

Writing inode tables: done                           
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 29 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

Note the parameter "-m 0" which overrides default 5% of the file system reserved for the root user.

I have previously created directories /mnt/source and /mnt/target which will be used for copying the data that was stored on the DNS-323

With a couple of commands I am going to mount both RAID arrays
# mount /dev/md1 /mnt/source
# mount /dev/md0 /mnt/target

and verify that it was done correctly:

#df
/dev/md1             958846504 756342136 202504368  79% /mnt/source
/dev/md0             960404232     73364 960330868   1% /mnt/target

Finally I can kick-start the data transfer process:
cp -av /mnt/source/* /mnt/target/

and watch the progress of the copy job:
watch -n1 df -h

The copy process runs at 4GBytes/min.

When finished we can take down /dev/md1, rebuild the partition table on /dev/sdb2 and add the fixed disk to /dev/md0

# umount /dev/md1
# mdadm --remove /dev/md1
# fdisk /dev/sdb

I am not going to repeat the commands for deleting and creating the second partition, follow the same as above for /dev/sda.

# mdadm --add /dev/md0 /dev/sdb2
mdadm: added /dev/sdb2

You can watch the progress of syncing RAID 1 using:
watch -n1 cat /proc/mdstat

It runs at 90 MBytes per sec or 5.4 GBytes/minute. Since it syncs the entire disk (not only the data) it will always take approximately 3 hours on 1 Terabyte.

Finally after shutting down the linux PC you can insert the disks back into DNS-323, turn the D-link on and after a bit of negotiations the RAID1 is fully recognized as being clean and fully in sync.
For some reason it can take up to 10 minutes for DNS-323 to boot up from the PC created RAID array, all subsequent boots are within 90 seconds, which is the normal startup speed.

- SD

Last edited by skydreamer (2008-07-12 23:22:26)