ReadyTIER with iSCSI

Yep, the 3200's onboard Broadcom SAS1068E is SAS1, so it only supports up to 2TB drives and only 3Gb/sec. max.  Now, I have wondered if putting an LSI SAS 2008 (SAS2, size limit unknown, 6Gb/sec) based controller in and disabling the Broadcom would fix that.  The onboard SAS controller for the 4200V2 is the LSI, so the ReadyNAS kernel does have support for it.  You'd need a couple SFF-8087 to SATA cables (Supermicro CBL-0288L-01 or equivalent) to connect the LSI to the backplane.  Since the backplane doesn't include a SAS expander, it will work with the bigger drives (4200V2 uses the same one).

The LSI controller would likely need to be in "IT mode" (a different firmware than for built-in RAID) for the NAS to properly utilize the drives individually to build the software RAID.  But it's easy enough to buy one on eBay that already has that, as it's a popular controller for FreeNAS, which also requires IT mode.  The first question in my mind is whether the onboard SAS BIOS of the 4200V2 is a Netgear edition and, as with the the main board BIOS, ReadyNAS OS will refuse to run on it if it doesn't have that signature, which the added card in a 3200 won't have.  I rather doubt they'd go that far, but it would be a way of preventing the 3200 from being made closer to the 4200V2 in capability.  The other question is whether it will know that the drives connected to the LSI controller are bays 5-12 when the configuration in the USB flash says it's a 3200.  If it doesn't, you could delete the VPD file that contains that and hope it then just thnks it's running on a 4200V2, but you'd also lose the serial number (and thus ReadyCloud capability)..

I do want to emphasize that that previous paragraph also means you can't replace the X7SB3 board in the 3200 with a generic SuperMicro X8SI6 and effectively get a 4200V2.  I tried to do that as a repair, and once the kernel on the internal USB boots, it stops before passing control to the OS on the drives.