The DNS-320 gigabit NAS has been around for some time now. I recently picked one up at a local CompUSA for under a hundred bucks. Adding a couple of Western Digital 2-TB SATA drives for around $80 each should provide some temporary relief for my disk space shortage problem at home.

Issues

In the past I reviewed the DNS-321 and the major complaint there was the device’s inability to utilize gigabit network capacity due to severe memory and CPU restrictions. While the DNS-321 was initially built as a 100-Mbit NAS and later converted to gigabit, the DNS-320 was built as a gigabit-capable storage device from the very beginning. It is still a very flimsy-looking plastic box filled with cheap components. If I am lucky, it may run for a year or two before the cooling fan fails or the power supply burns out.

How hard was it to configure DNS-320, I hear you asking? Surprisingly, not very easy at all. It took me – a senior Unix sysadmin – and a colleague – an experienced network admin – about two hours to get this little box working. The problem was the network: during the first-time setup, the DNS-320 can only be accessed if you have a DHCP server running on your network. With the DNS-321 you could just hookup your laptop via a crossover cable and configure the network manually by connecting to the default IP address of 192.168.0.1. With the DNS-320 we had to install and configure a DHCP server on an OpenSuSE box just to get to the Web interface.

The Web interface itself is not standards-compliant and doesn’t work with Firefox running under Linux. After I finally managed to get the DNS-320 on the network, I had to use IE on my Windows 7 laptop to configure storage volumes. Another annoying issue with the Web interface is the very short default session timeout period. Fortunately, this setting can be adjusted. What cannot be changed are the volume names. If you have multiple D-Link NAS systems on your network, things can get a bit confusing:

Configuration

The DNS-320 lets you chose from four volume configuration options:

Standard – creates one volume on each disk (Volume_1 and Volume_2). This configuration offers no redundancy and no performance gains. However, it simplifies data management and allow using external applications to mirror data between volumes. The DNS-320 has the ability to backup itself to another NAS (doesn’t have to be a D-Link) using FTP.

JBOD – creates a single volume that spans both disks. This gives you a large single volume (up to 4 TB with dual 2-TB disks). However, the chance of data loss increases, since if any one disk fails, the entire volume will fail.

RAID 0 – creates a single striped volume using two disks. Arguably, this is a nearly useless feature for this particular system, since even one SATA disk has higher I/O than the gigabit network through which the data is being accessed.

RAID 1 – creates a single volume with data mirrored across the two disks. If one disk fails – which, with the way quality of hard drives is dropping, will happen in less than a year – the data should still be preserved and available on the remaining disk. Naturally, you end up with only 50% of usable disk space. The front panel of the DNS-320 has an LED for each disk. If a disk fails, the LED turns yellow (or red), at which point you will need to power the system down (it is not hot-swappable) and replace the failed drive with another disk of the same geometry. Once you power up the system, it should start rebuilding the RAID set. During this time the data should still be available to you.

The two practical options for volume configuration are Standard and RAID 1. If you use standard, you can use an external application (simple case: rsync running on a Linux box NFS-mounting volumes from DNS-320 or just have two DNS-320s cross-backup data to each other) to mirror your data between the DNS-320 and another network storage location. This would be more secure than using RAID 1 on a single DNS-320. As I already mentioned, the box is cheaply made and the chance of the entire enclosure failing is probably as high as that of a disk failure.

Once you have configured your data volume, there are a few configuration changes that I would recommend to improve performance and lower the risk of data loss:

Go to Management -> System Management -> System Settings -> Idle Time and change the idle timeout to something considerably longer than the default five minutes.

In Management -> System Management -> Power Management: disable HDD hibernation, enable power recovery, set fan to auto low/high, and leave power off disabled.

In Management -> System Management -> Notifications: configure and test outgoing email. It is important to be notified of disk errors and overheating incidents before they cause irrecoverable data loss. That’s why I wan to recommend this uk based heater panels. You can configure DNS-320 to use SMTP-compatible mail service, such as Gmail.

In Management -> System Management -> Time and Date set the correct time zone for your location and specify the NTP server (you can select one from the drop-down or use a public NTP server, such as pool.ntp.org).

Once you done configuring your DSN-320, go to Management -> System Management -> System Settings -> Configuration Settings and save the configuration file to your computer (not to the DNS-320 file share, of course). After that I would recommend rebooting the DNS-320 just to see that everything is still working as expected. To reboot go to Management -> System Management -> System Settings -> Restart

Performance

For the test I was using a gigabit network with no other traffic, firewalls, or anything else that may introduce inconsistencies. The first simple test was to copy about 80 GB of data (just some potpourri of files I had in the My Documents folder) from my Windows 7 PC to the mounted DNS-320 network share via the Windows Explorer (simple copy-paste). Data transfer rate for uploading was in the range of 5-17 MB/s and for downloading: 7-23MB/s. Whenever transferring files over the network, you need to keep in mind that a few large files will always go through faster than many small files, even if the overall amount of data being transferred is the same.

The second test involved transferring the same 80 GB of data over FTP. Being the File Transfer Protocol, it is of no surprise that FTP transfer went much faster: 20-28 MB/s for uploading and 23-32 MB/s for downloading.

The last test was to NFS-mount the DNS-320 volume on a Linux box and run the Bonnie++ test on that filesystem. The bonnie++ syntax for this test was:

bonnie++ -n 0 -u 0 -r `free -m | grep 'Mem:' | awk '{print $2}'` -s $(echo "scale=0;`free -m | grep 'Mem:' | awk '{print $2}'`*2" | bc -l) -f -b -d /nas2

In this case the /nas2 filesystem was NFS-mounted from the DNS-320 on an openSUSE 11.1 server with gigabit connectivity to the same subnet as the DNS-320. The command above automatically checks system memory and uses twice that amount to run a valid filesystem performance test. Here are the results of the test:

Using uid:0, gid:0.
Writing intelligently...done
Rewriting...done
Reading intelligently...done
start 'em...done...done...done...
Version 1.01d       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
icebox        4000M           15810   2 10684   2           28914   4 119.5   0
icebox,4000M,,,15810,2,10684,2,,,28914,4,119.5,0,,,,,,,,,,,,,

Conclusion

For less than a hundred dollars, the DNS-320 is a good storage solution. Performance-wise, this small NAS will not win any awards. But for the money you are paying, it offers useful capabilities. It is fast enough to be a practical backup solution for your home PCs. The initial configuration is unnecessarily complicated for a home network that doesn’t use a DHCP server. The DNS-320 should have been configured to fall back to the default management interface IP address if DHCP was not found.

The cheap plastic cooling fan cannot be easily replaced, which is a pity, because it looks like something likely to fail. The small, overheating power supply made in China by the Asian Power Devices, Inc. looks like something that will fail before or shortly after the cooling fan. But the power supply should be simple enough to replace.

Whatever goes first is not that important. My point is that even with RAID 1, your data is far from secure when using such low-end storage systems. The solution is to either upgrade to a storage system that wasn’t built on a twenty-dollar budget, or to increase redundancy by adding more cheap NAS systems to your network to spread out the risk.