Just want to get this out of my head so that I can go back to sleep...
I've been taking a sabbatical after 3 years with Zapp (2 years as Chief Architect) and have been doing a number of personal projects. One of the projects was to sort out my NAS setup as I was running out of space on my ReadyNAS NV+ V2 and wanted to play around with fitting larger disks.
I decided to experiment with installing non-officially supported 6TB Western Digital NAS drives as their siblings (WD10EFRX/WD20EFRX/WD40EFRX) are supported.
I can only report failure though possibly with a glimmer of hope for others...
My previous configuration had 4 x WD30EZRX (3TB) drives in an X-RAID2 setup. After backing up I started to try out hot swapping out the drives individually and resynching before rebooting to realise the increased capacity.
The first problem was that the screws that came with the ReadyNAS were A2 Countersunk UNC 6 32 1/4" screws. To mount the WD60EFRX you need 3/16" or even 5/32". A little careful work with some abrasives took care of that as I was impatient.
Over the course of 4 days of swapping and resynching (each resynch took ~16 hours) I was ready for the reboot. The resynch had gone swimmingly!
At reboot is when things started to go wrong as the expansion failed and it started resynching the drive. All reboots after resynch completion failed to expand the volume and resulted in a resynch.
Next attempt was to clear the drives down completely (including the existing partitions) and perform a factory reset (boot menu button accessed via a pinhole by the USB, choose 'Factory Defaults'). First I tried X-RAID2 default - file system creation error. Next I tried Flex RAID with a RAID 5 configuration - file system creation error.
I then decided to use the EnableRootSSH plugin and dig into the operating system to see what was going on... going into the detailed logging I saw that the creation of the ext2 filesystem on the large volume was failing.
Sleeping on it (until just now) I woke up with a realisation that ext2 is quite an old filesystem and may have some limitations. At a 4 KiB blocksize (which is what is configured into the ReadyNAS) it can only support up to 16 TiB volume size and file sizes up to 2 TiB. So while the individual drives are supported, the volume size that they created was not.
Ext2 (and ext3) do support up to 32TiB if the block size is 8KiB but the problem would be how to make the ReadyNAS set up the file system with this block size. I suspect that one could (using SSH) manually fix an incomplete setup by creating the volume with the larger block size and complete creating the media and backup directories.but that only pushes the limitation a little way down the road and may have all sorts of problems with hot-swapping drives in the event of a failure.
My solution was to buy a diskless ReadyNAS 316 enclosure which uses btrfs and tops out at 16EiB and definitely supports the WD60EFRX drives.
I hope that this post will help other people who may contemplate this experiment themselves.
