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[phgukx]

My DNS323 running with 2 disks in a JBOD configuration has worked flawlessly until recently when I now find disk 2 (HD_b2) has been mounted read-only (I see this from my Windows 7 machine).  Does this suggest there is a problem with it ? I tried D-Link Scan Disk from the NAS client which stopped at around 20% (I dimly recall the unit rebooted after this). Until now I've been running a cron-based overnight job to rsync my photo directories from disk 1 to disk 2. This means I don't have any important data on drive 2.

Can anyone help me resolve this ? What is strange is that I can still seemingly access all the directories & files on Disk 2 - though because it's r/o I can't add new directories.

My initial efforts with telnet & e2fsck resulted in:

/mnt # e2fsck -n HD_b2
e2fsck 1.41.0 (10-Jul-2008)
e2fsck: Attempt to read block from filesystem resulted in short read while trying to open HD_b2
Could this be a zero-length partition?

Any advice is much appreciated.

Thanks Paul

[ivan]

Please read up on how JBOD disks are setup.  Then make a complete backup to some other device of the data on your DNS-323.

What you are trying to do, backing up from one disk to another, should ONLY be undertaken if the disks are setup and formatted as standard individual disks. 

A standard JBOD setup links the disks together as far as the file system is concerned so while you have two disks you only have one virtual file system spread over both disks.  In that situation in one disk fails you have potentially lost all your data unless you have the time and money to attempt a recovery.  What you are seeing with the second disk being read only is typical because as far as the nas firmware is concerned disk 1 and disk 2 are part of a larger disk (the sum of both disks capacity less some overhead).

When you setup your disks you were offered 4 options in RAID Configuration.
1)   Standard (individual disks)
2)   JBOD (Linear - Combines both disks)
3)   RAID 0 (Striping - best performance)
4)   RAID 1 (Mirroring - Keeps data safe)

Of those 4 only the first will do what you want - backup from one disk to the other.  JBOD may appear to do so but in fact doesn't.  RAID 0 is a sophisticated type of JBOD and RAID 1 gives two copies of the data, one on each disk and if one disk dies it can be replaced and the data from the good disk will be copied over - the only way to lose data with RAID 1 if for both disks to die at the same time.