Upgrade the NAS containing 4x Seagate 500Gb with 4 newly purchased 2Tb drives. Western Digital Caviar Green WDC WD20EARS-00MVWB0 to be precise. This would take the available space from 1386 Gb to closer to 6 Tb 
TL;DR: It doesn’t work, have since reverted back to the 500GB drives.
UPDATE 24/1/12: I’ve been informed since I wrote this that you can get this to work with the latest 4.1.8 firmware but it does still require a factory reset so don’t waste your time swapping drives in one by one. – thanks Schaffer József!
This was going to be an easy job reading this as being hot swappable the X-RAID would do all the hard work for me. If you are about to do this save yourself some time and read on, it was not all as it seemed.
First job was removing trays – pushing the button did nothing. Turns out to be a common problem which you can get round using a pin or paper clip. Once you’ve done one its easy, all mine required this method of opening.
Then the new drive appeared DEAD like it did for this chap
Mon Dec 6 20:40:19 WET 2010 The disk attached to channel 1 could not be used. The most common reasons are RAID resync in progress, faulty drives, and disks that are too small to be added to the array.
After checking compatibility and upgrading firmware to 4.1.7 things seemed to be back on track..
Took a while though:
Mon Dec 6 20:44:32 WET 2010 A SATA reset has been performed on one or more of your disks that may have affected the RAID parity integrity. It is recommended that you perform a RAID volume resync from the RAID Settings tab ( accessible in the Volumes page => Volume tab in FrontView ). The resync process will run in the background, and you can continue to use the ReadyNAS in the meantime.
Mon Dec 6 21:01:34 WET 2010 Please reboot your ReadyNAS device to continue with the update process.
Tue Dec 7 01:53:41 WET 2010 Disk initialization started. The estimated time of completion is 17 hour(s) and 39 minute(s), at which time you will be notified via email. You can also check the progress in Frontview in the Volumes -> RAID Settings tab. Please do not shutdown the system while the initialization is in progress.
Tue Dec 7 01:55:22 WET 2010 System is up.
Tue Dec 7 08:59:34 WET 2010 Disk initialization successfully
Tue Dec 7 08:59:34 WET 2010 RAID sync started on volume C.
Tue Dec 7 12:16:21 WET 2010 RAID sync finished on volume C. The volume is now fully redundant.
One down, three to go, out with the paper clips again
Wed Dec 8 02:30:34 WET 2010 Disk remove event occurred on SATA channel 2.
Wed Dec 8 02:31:22 WET 2010 Disk fail event occurred on SATA channel 2. If the failed disk is used in a RAID level 1, 5, or X-RAID volume, please note that volume is now unprotected, and an additional disk failure may render that volume dead.
Wed Dec 8 02:31:31 WET 2010 A SATA reset has been performed on one or more of your disks that may have affected the RAID parity integrity. It is recommended that you perform a RAID volume resync from the RAID Settings tab ( accessible in the Volumes page => Volume tab in FrontView ). The resync process will run in the background, and you can continue to use the ReadyNAS in the meantime.
Wed Dec 8 02:36:11 WET 2010 Disk add event occurred on SATA channel 2.
Wed Dec 8 02:36:19 WET 2010 Disk initialization started. The estimated time of completion is 17 hour(s) and 39 minute(s), at which time you will be notified via email. You can also check the progress in Frontview in the Volumes -> RAID Settings tab. Please do not shutdown the system while the initialization is in progress.
Wed Dec 8 09:05:18 WET 2010 Disk initialization successfully finished.
Wed Dec 8 09:05:19 WET 2010 RAID sync started on volume C.
Wed Dec 8 12:17:02 WET 2010 RAID sync finished on volume C. The volume is now fully redundant.
Similar for disk 3, with paper clip
Wed Dec 8 12:26:52 WET 2010 Disk remove event occurred on SATA channel 3.
….
Wed Dec 8 21:32:03 WET 2010 RAID sync finished on volume C. The volume is now fully redundant.
and disc 4
Wed Dec 8 23:42:57 WET 2010 Disk remove event occurred on SATA channel 4.
….
Thu Dec 9 08:01:24 WET 2010 RAID sync finished on volume C. The volume is now fully redundant.
Then the system rebooted itself, but I later checked on it and saw
Thu Dec 9 08:10:39 WET 2010 The first stage of the in-place volume expansion is done. Please reboot the device to complete the volume expansion.
So rebooted again and left the building, only to come back later to find
Fri Dec 10 02:49:47 WET 2010 Disk capacity expansion error. resize2fs
Then it appeared that the expansion failed like this because it’s more than 5Tb so following the suggested factory reset I had to find places to backup almost a Terabyte of data! A little bit annoyed at this stage as I could have just replaced all the discs in one go had I known a factory reset was going to be required. But then I finally saw what I was working towards all this time
Online, X-RAID, 4 disks, 0% of 5533 GB used
I got there! or so I thought the next reboot hung in the “Booting….” state
Downloaded flash drive image here and created a USB boot with:
$ sudo dd if=ReadyNAS_USB_Flash_Recovery-4.1.7.img of=/dev/sdc1 133806+0 records in 133806+0 records out 68508672 bytes (69 MB) copied, 0.185484 s, 369 MB/s
Checking pat 1, 2, 3, 4, 5, this didn’t seem to end. I took the discs all out again to start adding one by one. Repeated this in a different order. Each time all went well until the last disk that would freeze at the same place on the resync (78%) on the fourth/last disk to be inserted. After a number of attempts (and also getting more concerned for the chances of losing data on other machines) I reverted back to the original discs. Performed a factory reset after finding RAID not enabled after the resync with all 4 originals, and then copied “everything” more selectively back on.
If interested I bought the drives from e-buyer (when they were going for £69.99) Pretty good, in fact I can now say most PCs in my home are fitted with one!
