... and monitor your RAID, scrub periodically and have notifications about component status. Unmonitored RAID equals no redundancy, because in this case you only recall there was a RAID when it was already failed below its survival mark.
Anyone have any ideas on how to retain the data that's on the drives?
There is no data on the drives. THere are fragments of data, but you literally ask how to put together a mirror from half the pieces.
There is something like common sense. Which includes backup - since 30 years or so. Ever since leaving school back then i have been told times and times ...
RAID is not a backup. If you have important data, take backups.
There are recovery options though, which have 0% - 100% probability of getting your data back.
The basic process is to take image copies of the hard drives to other hard drives, and then try to reconstruct the arrays from the images. To actually do this, you need to know how drives, RAID systems ...
This is what I ended up doing:
I returned the DX517 expansion unit because it couldn't be powered down (to carry offsite) without powering down the NAS. I didn't want that restriction.
I bought a second NAS (another DS920+ but that's likely overkill) installing the disks from the expansion unit and wiping them.
Then I installed "Snapshot Replication&...
Indeed the NFSv4 ACL and unix permissions on a single server confusing. However, at the end both apply to the same file system. The nfs server istself is stateless (kind of). The answers:
after you switch from v3 to v3 all existing files group and user ownership with stat as is.
if files already have ACLs (posix of whatever the under laying file system ...