|QNAP TS-879U-RP 10GbE NAS Server|
|Reviews - Featured Reviews: Network|
|Written by Bruce Normann|
|Monday, 19 March 2012|
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Benchmark Reviews primarily uses metric data measurement for testing storage products, for anyone who is interested in learning the relevant history of this sore spot in the industry, I've included a small explanation below:
The basic unit data measurement is called a bit (one single binary digit). Computers use these bits, which are composed of ones and zeros, to communicate their contents. All files are stored as binary files, and translated into working files by the Operating System. This two number system is called a "binary number system". In comparison, the decimal number system has ten unique digits consisting of zero through nine. Essentially it boils down to differences between binary and metric measurements, because testing is deeply impacted without carefully separating the two. For example, the difference between the transfer time of a one-Gigabyte (1000 Megabytes) file is going to be significantly better than a true binary Gigabyte (referred to as a Gibibyte) that contains 1024 Megabytes. The larger the file used for data transfer, the bigger the difference will be.
Have you ever wondered why your 500 GB hard drive only has about 488 GB once it has been formatted? Most Operating Systems utilize the binary number system to express file data size, however the prefixes for the multiples are based on the metric system. So even though a metric "Kilo" equals 1,000, a binary "Kilo" equals 1,024. Are you confused yet? Don't be surprised, because even the most tech savvy people often mistake the two. Plainly put, the Kilobyte is expressed as 1000 bytes, but it is really comprised of 1,024 bytes.
Most network engineers are not fully aware that the IEC changed the way we calculate and name data chunks when they published the new International Standards back in December 1998. The International Electrotechnical Commission (IEC) removed the old metric prefixes for multiples in binary code with new prefixes for binary multiples made up of only the first two letters of the metric prefixes and adding the first two letters of the word "binary". For example, instead of Megabyte (MB) or Gigabyte (GB), the new terms would be Mebibyte (MiB) or Gibibyte (GiB). While this is the new official IEC International Standard, it has not been widely adopted yet because it is either still unknown by institutions or not commonly used.
NAS Testing Methodology
All the NAS devices we test cannot accommodate all the different disk configurations, so our current test protocol is based on two of the most popular setups: a basic (single) disk and RAID-5. Most NAS products that can support RAID 5 go beyond the minimum number of drive bays, to a total of four, so that is the number of drives that I typically use to test with, even though I could get by with only three. I took advantage of the massive capacity that the QNAP TS-879U-RP offers, and tested it with the full complement of eight identical drives. During initial setup, the NAS was upgraded to the latest v184.108.40.2066 firmware by flashing the DOM with binary files from QNAP's website. The firmware installed on the TS-879U-RP was v3.4.3.0331 when I received it, and the same version was included on a CD-ROM provided in the accessory kit.
The emphasis for this round of testing was to see how much faster the QNAP TS-879U-RP could run, once the GbE bottleneck was removed. To accomplish that, we installed Intel 10GbE NICs in both the NAS and the host PC. QNAP has several 10GbE options on their list of compatible NICs, and I chose the Intel X520-T2 model (E10G42BT) to install in the NAS, as it is one of the few models that directly supports regular CAT6 cables. For the host PC, I had pretty much free reign to choose, as long as I stuck to copper wiring. I decided on the Intel E10G41AT2 because I wanted to ensure network compatibility, and because of my positive experience with Intel NICs in the GbE world. Their drivers and utilities have been top notch, with a very comprehensive feature set, and easy to use. I have no need for long cable runs in my test area, but those that do will want to look at models that support fiber optic cables. CAT6a cables are good for 100 meter wire runs with these two NICs, which is about 97 meters longer than I needed.
With the 10GbE network physically in place, all tests were conducted with Jumbo Frame enabled, i.e. the MTU value for the Ethernet controllers was set to 9000. All the NAS products tested to date in the Windows 7 environment have supported the Jumbo Frame configuration. With only one port available on the Intel E1041AT2, the two NICs were not able to operate in IEEE 802.3ad mode, commonly called Link Aggregation Control Protocol (LACP). In a Windows environment, with one host PC and one NAS, LACP does not provide twice the bandwidth, unless there is an equal amount of data being sent and received at the same time. In a multi-user situation, with the appropriate network switches in place, you are more likely to see the benefits of Dynamic Link Aggregation. I used Intel's Advanced Networking Services (ANS) driver on the host PC, which is standard issue with their high-end NICs.
With the network up to speed, the next potential bottleneck that needed attention is the disk system on the host PC. In previous tests, we relied on the third generation OCZ Agility SSD, which is good for at least 500 MB/s, input or output, on the appropriate Intel Platform Controller Hub. QNAP has achieved over 1500 MB/s with the TS-879U-RP in their tests, so it was time to bypass the SSD on our test rig and install a RAM Disk. There are at least a dozen products on the market that will create and manage a RAM Disk on Windows systems; I chose RAMDisk v220.127.116.11R22 from Dataram based on performance tests in several reviews (we read 'em, too....) and its reasonable cost structure. I needed to assign at least 10GB of space to the RAM Disk, in order to replicate the test protocol I've been using for all my NAS testing, so none of the freeware products looked suitable. One other trick was necessary, to get the RAM Disk to access files larger than 2GB, I had to use the Convert utility in Windows 7 to make the RAM Disk an NTFS volume. Then I was able to perform the file transfers with 10GB files, no problem. If you want to avoid this extra step, be sure to look for a RAM Disk product that directly supports the NTFS file system.
The actual throughput testing followed our standard methodology, with the NAS directly connected to the LAN controller in the test-bench system by ten-foot CAT6 patch cables. The NAS product receives one test transfer followed by at least three timed transfers. Each test file was sent to the Western Digital Caviar Black 750GB (WD7502AAEX) hard drives installed in the NAS for a timed write test, and that same file was sent back to the RAMDisk in the test system to perform a read test. Each test was repeated several times, the high and low values were discarded and the remaining results were recorded and charted.
In addition to straight throughput testing, I also ran the ATTO Disk Benchmark on the NAS, which is easy to do once a drive mapping is created on the host PC. Our standard test settings use a queue depth of 4, and I also ran additional tests with the maximum queue depth available in this benchmark, which is 10.
For the first time, I also ran the Intel NAS Performance Toolkit (NASPT) version 1.7.1, which was originally designed to run on a Windows XP client. People smarter than me have figured out how to run it under Windows 7, including the 64-bit version that is used more often than the 32-bit version these days. Like most computer gurus, they openly shared their new-found knowledge with the rest of us, and now we can duplicate and expand their results. NASPT brings an important perspective to our test protocol, as it is designed to measure the performance of a NAS system as viewed from the end user's perspective. Benchmarks like ATTO use Direct I/O Access to accurately measure disk performance with minimal influence from the OS and the host platform. This provides important, objective data that can be used to measure raw, physical performance. While it's critical to measure the base performance, it's also important to quantify what you can expect using real-world applications, and that's exactly what NASPT does. One of the disadvantages of NASPT is that it is influenced by the amount of memory installed on the client, and it was designed for systems that had 2-4 GB of RAM. Consequently, two of the tests give unrealistic results, because they are measuring the speed of the buffer on the client, instead of the actual NAS performance. For that reason, we will ignore the results for "HD Video Record" and "File Copy to NAS".
We are continuing our NAS testing with the exclusive use of Windows 7 as the testing platform for the host system. The performance differences between Win7 and XP are huge, as we documented in our QNAP TS-259 Pro review. The adoption rate for Win 7 has been very high, and Benchmark Reviews has been using Win 7 in all of our other testing for some time now. It was definitely time to make the jump for NAS products.
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