This thread http://www.silentpcreview.com/forums/viewtopic.php?f=7&t=63055
mentions the following:
"It's upped the platter capacity to 750GB and rotation speed to 6600rpm over the previous model."
I definitely want a 5400 model. The Hitachi Deskstar 5K3000
is 5940RPM. The Seagate Barracuda Green
sports a 5900 motor. So that leaves only the WD ones and Samsung F4 EcoGreen. The EcoGreen recording has a reasonably pleasant sound (to me) but loud seeks, the WD Red 3TB is pretty loud in comparison (I think) but the 1TB again has a nice character, so 2TB would be in between.
But WD Red has this "time-limited error recovery" that, according to the review, "is almost essential for RAID configurations to avoid data loss when errors are encountered". It is not really essential to avoid data loss, it is essential to avoid a disk being dropped by the RAID array under high I/O load when errors are encountered [article
]. The downside is that such disks cannot be used in non-RAID environments. I don't really understand how a disk can stop responding for a full 8 seconds while not crashing the system, but maybe it just stops responding to controller commands, I don't know. So the Red drives can only be used in RAID configs where there is redundancy in the form of a RAID 1 mirror, or RAID 5 parity - it seems - because otherwise the disk might postpone error correction causing sector reads to fail. But only under high load.
Your RAID dropping disks is pretty nasty. Something apparently often encountered by Synology users, in any case.