RN316 - Read Only status during resyncing task on EDA500 extension

The NAS usually puts a volume in read-only mode when it detects a problem with that volume.  It's protecting the data from further damage.  As StephenB said, it is critical that you back up data before re-booting.  After re-boot, the main volume may not even mount.

Before you re-boot, it may also be a good idea to EXPORT and disconnect the (fully re-synced) EDA volume.  If you end up having to factory default, you can later add an exported volume, but you cannot add a volume that wasn't.  And if you end up just having to destroy and re-create the main volume, the act of destroying it with the EDA attached will make the EDA volume primary, which is not a good situation with the eSATA multiplier interface it uses.  If all ends up well after the re-boot, or after you fix the problem, you just power down, re-connect the EDA and power up, which will automatically import the EDA volume.  Just make sure you don't duplicate any share names from the EDA if you have to start over with the main volume.

I suppose the problem with the main volume may have been caused in part by the re-sync of the EDA volume.  The eSATA interface is, frankly, a poor choice for the EDA.  An issue on the bus may have "spilled over" to the main volume.   But that "spill over" may be real damage to the volume or just a perceived one, which will determine whether a re-boot fixes it or not.

If you end up not having exported the EDA volume and later need to add it to a newly created main one, there is a work-around.  You put just the EDA drives in the main NAS, boot, then export.  That'll work for you since you have a 6-bay NAS.  But those with a smaller main NAS don't have that option.