The TS-421 was tested with 4.0.1 firmware using our standard NAS test process. Tests were run with four-drive RAID 0, 5 and 10 volumes. Times to completely build and resync 4 x 3 TB RAID 5 and 10 volumes were quite long at 17h 20m and 22h 30m, respectively. Unlike Thecus and Synology, QNAP does not offer the option to skip a bad block test, which can speed volume resync times significantly.
Note that in normal operation, volumes are ready for use after formatting is complete, which takes only a few minutes. But I need to wait until resync is completely done so that I can test performance without the throughput reduction caused by resync.
The Benchmark Summary below shows Windows File Copy write performance about the same (~44 MB/s) for RAID 0 and 10, but dropping to 36 MB/s for the more CPU-intensive RAID 5. File Copy read takes a different tack, with a slight upward trend from RAID 0 through RAID 10 (66, 72 and 73 MB/s).
QNAP TS-421 Benchmark Summary
NASPT File copy results are lower than their Windows File Copy counterparts across the board for both write and read.
iSCSI target write performance to target created on a RAID 5 volume at 28 MB/s was low compared to other four-bay NASes powered by single-core Marvell CPUs. Best in class is the NETGEAR ReadyNAS 104 at 41 MB/s. iSCSI read was better at 44 MB/s, but trailed the best in class Synology DS413j at 52 MB/s.
Best attached backup performance of 60 MB/s was obtained with eSATA / NTFS. USB 3.0 / NTFS backup measured only 46 MB/s.
For a competitive look, I ran filtered RAID 5 File Copy charts selecting three other single-core Marvell powered four-bay NASes for comparison, i.e. the NETGEAR ReadyNAS RN104, QNAP TS-412 and Synology DS413j.
All the compared products use single-core Marvell SoCs, but not the same model and clock rate. Even though the TS-421 has the highest clock rate (2.0 GHz), the comparisons show it's not the top performer. That honor consistently goes to Synology's DS413j, which uses a the same model SoC (88F6282) but clocked at 1.6 GHz.
RAID 5 File Copy Performance comparison
If you're looking for high performance, you shouldn't be looking at a SoC powered RAID 5 NAS, especially one that costs around $500. To get large filecopy performance up near saturating a Gigabit connection, you need at least a dual-core Atom. If you want a four-bay QNAP, you might look at the D2700 Atom-powered TS-469L, which will right now cost you only $50 - $60 more.
If you want your RAID 5 at the lowest cost and don't mind trading off performance, you might opt for the older TS-412 ($350) if you want to stay with QNAP. Or consider NETGEAR's brand-new RN104 ($308) or Synology's older DS413j ($380) as long as you are ok with not being able to hot-swap drives. Of course there's also QNAP's TS-420 ($424), which we'll be testing shortly, but should be in the ballpark with these other options.