I tested with 3.4.3 Build 0520T using our standard NAS test process.
The Benchmark summary below for the TS-412 shows Windows File copy write at 45 MB/s, with file copy read significantly higher at 74 MB/s. If you look at the File copy write and read charts, you'll see that all the TS-X12s measure 45 - 46 MB/s for RAID 0 write and 74 - 79 MB/s for RAID 0 read.
NASPT File Copy write benchmarks were higher and more evenly matched at 62 MB/s for write and 68 MB/s for read. As with all other tested NASes, the tougher NASPT Directory Copy tests didn't break out of the mid teens.
I ran backup tests to my standard Iomega Ultramax Pro in RAID 0 with USB 2 and eSATA connections and FAT, NTFS and EXT3 formats, courtesy of the 412's built-in formatter. Best throughput of 46 MB/s was with eSATA / FAT, while worst was 20 MB/s with USB 2 / NTFS.
Rsync network backup was even lower at 18 MB/s to the NAS testbed running Delta Copy.
iSCSI write and read to a 10 GB target on a RAID 5 volume produced 26 MB/s and 48 MB/s, respectively.
The RAID 5 File Copy Write and Read charts below are filtered to show only four-bay NASes. The 1.2 GHz Kirkwood is used by older NASes like the Buffalo TeraStation ES, Iomega ix4-200d and Seagate BlackArmor NAS 440. So QNAP is mainly trying to keep the TS-412's selling price down, its margins up or both by using it.
That said, the TS-412 seems to do well against these older NASes. But keep in mind they were tested on the previous-generation NAS testbed.
RAID 5 file Copy Write Comparison - four bay products
You can make an apples-to-apples comparison with the Buffalo TeraStation Pro Quad (D510 Atom) and QNAP TS-419P+ (1.6 GHz 88F6282 Kirkwood), since they were also tested on the same current-generation testbed.
While the TS-412 does pretty well against the Atom-powered Buffalo on RAID 5 write, it can't keep up on RAID 5 read. It's surprising that the 1.6 GHz Kirkwood TS-419P+ does so much better on RAID 5 read than the TS-412, but there you are.
RAID 5 file Copy Read Comparison - four bay products
If your heart is set on a four-bay QNAP but your budget is tight, the TS-412 can save you almost $100 vs. the TS-419P+, the current high-end of QNAP's "Home and SOHO" line.
Price vs. Performance - four bay products - RAID 5 write
But you will sacrifice some performance to keep more money in your pocket. If you want 2 TB of storage for about the same price, you might consider the Buffalo TeraStation Pro Quad if it has the features you want. But it looks like Buffalo needs to do some tweaking to get more performance out of its D510 Atom.