Network Attached Storage - A question of sharing

Network attached storage (NAS) is hard disk storage, and a term that has proved a dream for many marketing departments determined to confuse companies with black-art terminology.

As the name suggests, the hard disk is attached to a local are network and has its own network address, rather than being on a single department's server, so everyone has access to this common space. As per-gigabyte hard drive prices fall, these small solutions are becoming increasing common in the workplace.

Inside the box, one or more IDE drives provide space from a small hard drive (for instance, 40GB) at the cheaper end of the market to Raid configurations providing over half a Terabyte as you spend more money.

There usefulness is varied, from a traditional backup device - like tape drives but infinitely faster - to a shared folder on the network. Additionally, if the system supports HTTP or FTP, it can be used to exchange files over the Internet.

In practice, these appliances offer other facilities, particularly those aimed at the small business or domestic market. Among those we group tested, this included models that come with their own wireless access point, or others acting as a USB hard drive.

Here we look at six to see how they perform. Click here to read about each.

How we tested
When assessing performance of these kinds of devices, we needed to establish how they behave when copying, reading and writing files of several sizes in different 'blocks' and in different ways.

We used an Open Source application called IOzone, which runs under both Windows and Linux. This analysis, which we can adjust at will, accesses a file of any size we tell it (in this case 640MB), writing and reading sequentially, randomly and repeatedly.

Also, every access is in varying block sizes, starting from 64MB to the entire file. In this way we arrive a KB/sec figures in each mode, so we can see how the appliance performs when accessing files of every type.

Every appliance in our comparison took some six hours to perform the test, so the amount of data transferred was considerable.

In addition, we tried working with 10MB files simultaneously, using up to five independent processes in each measurement. In this way we got a picture of scalability (number of clients supported simultaneously), performing several reads and writes at the same time.

All tests were carried out using the same machine, with an Ethernet Gigabit card in 100Mbits/s mode, connected to an Intel switch with a VLAN between two ports: the NAS and the machine itself. At all times the number of packets passing through the ports was monitored to establish that the appliance was not overloading.

The tests were run under Windows XP SP2, and we also found that in some cases a Samba client (under Kernel 2.6) was slower (even on the same machine) than XP.

Editor's choice
We have no doubt as to what the differences are between enterprise and small office or home NAS appliances. The former are capable of supporting heavy workloads with multiple users accessing simultaneously, while the latter tend to focus their efforts on just one.

So, when choosing a professional solution for a workgroup, our editor's choice has to go to the Iomega NAS 300. It is scalable, with good performance and is very simple to configure, even though it is fully customisable. Though its price per GB is high, because rack formats increase costs, but it is a comprehensive product.

On the other hand, we have devices aimed solely at the small to medium market. While Ximeta offers a very small and lightweight solution, it is expensive when compared to others with more capacity and similar orientation, as in the case of the most basic Iomega or even Asus models.

The former is a simple and efficient device, ideal for anyone requiring a portable hard drive reluctant to delve into security issues. The latter offers numerous options in spite of its small size. On the down side, it is not very fast because of the 2inch hard drive it houses, and some aspects of its interface could do with some improvement.

Clearly top marks in this respect go to Linksys because of its performance, utilities and retail price.

But our highly commended goes to Snap Server. It was easy to configure, thanks to its clear instructions and user friendly interface, and its performance was good. We felt the price was a bit steep, but this does not detract too much from what is otherwise a good product.

Like this story? Spread the news by clicking below:

 del.icio.us     Digg this     reddit!