Testing and Performance
We ran into a few unforeseen problems when it came to testing the N5200 Pro; first of all one of the Western Digital Caviar SE WD800 80GB hard drives that Thecus lent us for review had too many bad sectors, so we had to limit the RAID 5 to three drives instead of the planned four which affected the performance to a degree, although it's not a major issue. These aren't exactly cutting edge hard drives, but at least they're 7,200RPM drives with 8MB buffer.
Once we started testing the N5200 Pro, we realised something wasn't quite right as during copying tests to the NAS we didn't get above 20MB/s which seemed way too slow considering we used a Gigabit Ethernet setup as well. It turns out that the drivers provided by ASUS for the motherboard inside the test system were out of date. Finding some new drivers from the manufacturer of the network controller solved this problem and we peaked at over 80MB/s during synthetic tests and well over 40MB/s during copying from the device and 30MB/sec to the device.
A limiting factor here as well was the fact that the hard drives in the test system couldn't match the speed of the RAID array inside the N5200 Pro, so we couldn't throw enough data at it to really push the boundaries, hence the higher numbers in SiSoft Sandra and HDTach. Unfortunately we couldn't get I/OMeter to behave properly, as it would've been an interesting benchmark to run on the N5200 Pro. None the less, we tested it with some FTP file transfers and with both SiSoft Sandra and HDTach thanks to its iSCSI functionality; this enabled us to use these benchmarks with a NAS, something that you can't normally do.
Using FlashFXP we did two different kind of copy tests, the first one consisted of a single large 5.83GB ISO image file which copied to the NAS in 3 minutes and 18 seconds at an average speed of 30.1MB/s. From the NAS onto the same hard drive took 2 minutes and 20 seconds and this was at an average speed of 42.57MB/s. That is Megabyte per second, not Megabit per second which you get when you're downloading files over the internet. This is pretty fast and we have no complaints.
The second FTP test used 19 smaller files ranging in size from about 170 to 250MB per file and totalled up 3.31GB of data. This took 1 minute 58 seconds to copy to the NAS at 28.83MB/s. Copying the files back onto the PC took 1 minute 22 seconds at 44.88MB/s. You can see the results as well as the SiSoft Sandra and HDTach read speed results on the following page. For some reason SiSoft Sandra refused to write to the drive as the benchmark claimed that the drive wasn't empty even though it clearly was.
The iSCSI partition on the NAS was reported to be a 15,000rpm SCSI drive in SiSoft Sandra and the random access time was some 12ms. We also tested both SiSoft Sandra and HDTach with a USB partition on the N5200 Pro, but here we ran into another odd limitation as neither benchmark would go above 12MB/s or 88Mbit/s which is very strange as USB 2.0 can manage 480Mbit/s or 60MB/s. We have no idea why this was the case. HDTach reported a random access speed of 11.1ms via iSCSI and 12.3ms via USB. The CPU utilization was fairly high at 15 percent when using iSCSI, but the iSCSI initiator has some overheads here.
The Average read speed in HDTach was about 41.3MB/s using iSCSI and 11.2MB/s over USB. The burst speeds using iSCSI were significantly higher as you can see from the graph below, but not so with USB. Overall we're quite impressed by the performance of the N5200 Pro and it should prove to be one of the faster NAS products in its range. There's a lot of competition in this market segment and we'd only expect it to get even more competitive.