|QNAP TS-259 Pro Turbo NAS Server|
|Reviews - Featured Reviews: Network|
|Written by Bruce Normann|
|Monday, 03 May 2010|
Page 9 of 13
Benchmark Reviews has decided to abandon our effort to educate readers on the difference between a Gigabyte, and a Gibibyte. This article will use the common metric terminology for data measurement, instead of the binary units we've used in past articles. Sadly, too many people are more interested in comfortable reading, even if it means being technically inaccurate. But for anyone who might still be interested in learning real technical terms relevant to the industry, I've added 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 (myself included) 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.
Personally, I think the IEC took a confusing situation and simply made it more of a mess. As I mentioned earlier, the Kilobyte was previously expressedas 1000 bytes, even though it was really comprised of 1,024 bytes. Now, the Kilobyte really is expressed correctly as 1000 bytes, and the Kibibyte is the item comprised of 1,024 bytes. In essence, the IEC just created a new name for the binary item and left the existing name for the metric item. Hopefully that clears things up, and you can thank Benchmark Reviews for training the next generation of Network Engineers.
NAS Testing Methodology
Although the device we tested can accommodate several different disk configurations, all of our current test data has been with basic (single) disk and RAID-5 configurations. Since this two-bay device cannot support RAID-5, I tested only the single disk mode.
Connected directly to the Realtek RTL8112B PCIe Gigabit Ethernet NIC in the test-bench system by a ten-foot CAT6 patch cable, the NAS product receives one test transfer followed by three timed transfers. Each test file was sent to the Western Digital Caviar Black 750GB (WD7501AALS) hard drives installed in the NAS for a timed write test, and that same file was sent back to a Western Digital VelociRaptor 150GB 10,000 RPM (WD1500HLFS) hard drive in the test system to perform a read test. Each test was repeated, and the first three identical results were recorded and charted.
The two transfer tests: read and write, were conducted on each NAS appliance using the 1 GB file and then the 10 GB file. Additionally, a second set of tests were conducted with Jumbo Frame enabled. While the Synology Disk Station DS209, DS408, Cube Station CS407, and QNAP TS-409 Pro/TS-209 Pro each offered 9000K MTU Jumbo Frame settings available, the D-Link DNS-323 and QNAP TS-509 Pro do not. In some Jumbo Frame tests the Realtek RTL8112B Gigabit NIC was limited to a maximum of 4074 for the MTU value, with Jumbo Frame enabled.
NAS Comparison Products