Home > Consumer Reviews > D-Link 2-Bay Network Attached Storage Enclosure DNS-321

I've been pleased with the reliability and performance of the DNS-321. I was hoping the Gigabit transfer speeds would be significantly faster, but it seems to top out at 14-16 MBps (MegaBytes per sec). This is on the upper end of most consumer NAS boxes, including D-Link's tried & true DNS-323.

Pros:
. Runs cool & quiet.
. Spins down the HD when idle to conserve power.
. Rock-solid operation (no reboots necessary in the month I've had it).

Cons:
. Larger drives (1TB and up) can get "stuck" at 94% during the format phase, but eventually it will complete.
. User permissions setup is clunky. This is common among consumer-level NAS boxes though.
. User access permissions are cleared on reboot :(
. No firmware update yet (v1.0). D-Link tech support says they've fixed most of the problems above and are testing the new firmware for public release. The cons are relatively minor to me, and once fixed in firmware, this will be a 5-star product.

Notes:
Opt for a low-power (and low-heat) HD to use in an external enclosure. Transfer rates on this generation of NAS will never approach the max throughput of HDs, so using a fast 7200rpm drive is a waste of money and power. Extra heat from the faster drives may cause issues down the road. Recommended low-power models are the Western Digital GreenPower and Samsung EcoGreen.


UPDATE 11/30/2008: D-Link has released firmware 1.01 which fixes the issue with access permissions being cleared on reboot. It also claims to support 1.5 TB hard drives.
http://support.dlink.com/products/view.asp?productid=DNS-321

UPDATE 5/8/2009: User account access control has an issue in all firmware versions, from the original 1.0 release to the latest beta. Basically the setting to allow All users to access a share disappears. Resetting to defaults sometimes brings it back, but shares configured to allow All users don't work properly. Weird issues with the All checkbox and shares disappearing are very frustrating. Dlink tech support has been aware of this for 4-6 months but no fix is in sight.

I now rate this at 3 stars.

Well, it was working fine for the features I was using. Immediately updated to their latest firmware release. Put 2 1TB drives in it, all the backup options (rebuild drive, etc.) seemed fine as I played around with swapping drives out. Then I tried to copy all of my current data over to this NAS box. After about a full day of copying (I have several hundred gigs of files) I went to check the status of the backup.

The backup had completed... HOWEVER, since I had turned on data validation (rereads the destination and source files and compares after the backup) it noted that out of the 1000s of files I had backed up that 12 of them were "not equivalent to the source files".

I took down the names of the files and then did a hex dump compare of the old and new files. To my surprise the files that were copied onto the NAS box had *exactly* 76 bytes of zero in very specific relative offsets in each file. It was always at hex offsets with the last 3 nibbles of the file offset being in the range of xfb4-xfff that were all zero, in all of the "corrupted" files.

Puzzled, I did some Google searching and found that there was a Linux kernel bug found at the end of 2006 that just happens to exactly match this behavior! The kernel was losing the "dirty bits" (modified memory page indicators) when it was writing to ext2 or ext3 file systems (this box uses ext2). This only happened on certain "chunks" (76 bytes for the Linux case) if they were the 76 bytes that fall at the end of a 4k memory page boundary (the last 76 bytes of a 4k page are... you guessed it!! bytes xfb4-xfff).

The data I was transferring was from a Windows XP machine and this NAS box is internally running.. yep, LINUX! I believe they likely have a version of kernel running on this thing that was silently corrupting my data, as all the issues seem to exactly match my conditions.

That is the WORST kind of data corruption ("silent") because there were NO error indications at ALL except for when it had done the final recompare, which good thing I had turned that on or I would have NEVER known my data was being corrupted as it was copied to this NAS box!

I notified the D-Link tech support people about this issue, and they responded back saying that they are looking into what is causing the problem (think I gave them a good enough head's up on this one!)

I promptly returned the box to get my money back and am now running w/ a RAID 1 configuration in my main PC instead of having an external NAS box.

Support notes - I stayed on the phone for the D-Link tech support number for a good 20+ minutes, all I got was the answering service kept repeating "due to a large volume of calls, ... " so I just hung up and emailed them instead. Took them about a week to get back to me (but they did).

Other gripes about the box - the little levers to remove the drives were REALLY hard to use, my thumb got sore after swapping the drives a couple times for doing the failed drive testing.

This review is specifically about the DNS-321 as that was the only one I tested, however the DNS-323 is VERY similar to this box (just basically added a print server), so I can't say if that one is any better or does the same corruption as this one does (it's quite possible).

If you are looking to add storage without the hassle of internal drives then this is a great device.

The setup is easy and there are plenty of configuration options via an easy web GUI. It uses the EXT2/linux file system so fragmentation is not a problem.

I have two 1 TB drives set in a raid 0 for testing purposes and this thing screams on a gigabit network.

It is a very small and quiet and looks sleek.

Overall this is the best home/small business diskless NAS system out there.

I bought this to test as an inexpensive file server in a small business, so I cannot comment about the UPnP server, FTP server, etc.

The unit ships with firmware v1.00, but that firmware has problems (RAID, large drive, fan settings, etc.) that are well documented, but firmware v1.01 was released in October 2008, and was supposed to fix those issues.

I immediately updated the firmware to v1.01 and began to test the RAID for reliability, etc. It turns out that v1.01 broke some important items for me - most notibly the permissions. As soon as you create a single user, the ability to select "All accounts" disappears. Further, every time you reboot the unit, you will lose all of the permissions that you set up. This is a bug, and D-Link is well aware of it since early November 2008 - you can read about it on their forums. It is now early March 2009, and they have not released an updated firmware.

I have it turned off and sitting on the shelf waiting for a new version of the firmware. If they fix it, this could turn out to be a nice unit, but until then, stay away if you want a reliable file server with RAID for a small business.

I've set up perhaps 10 different NAS boxes/servers over the last few years, I have 3 attached to my network currently - this Dlink DNS321 and two LaCie drives. This is by far my favorite for several reasons. For the price, its great that you get an expandable NAS box that supports RAID and any size drives you want to put in there. Its remarkably easy to install the drives, so even if you have no experience installing hard drives into a computer don't worry, its impossible to mess it up as they just slide in - buy OEM drives as you don't need the cables/screws that come in retail boxes. The other big reason I prefer this device over the other NAS drives I have and have had in the past is the speed. By consumer NAS drive standards, its a speed demon. I get roughly 6MBps as a solid connection over my wireless n network with 7.5MBps peaks and 14MBps over my gig LAN connection which are both about 50% faster than either of the LaCie drives that I also have currently connected.

Couple of pieces of advice if you buy this device. If you are only installing 1 drive at first, put it into the right bay as it will make things easier down the road (why? http://support.dlink.com/faq/view.asp?prod_id=2531&question=dns%2D321). Secondly, if you use Mac's, be aware that although these drives work very well with Mac's of course, the software Dlink gives you on the CD is Windows XP/Vista only. Although installing the device is very easy, setting it up isn't what I'd call straight forward so it helps if you've set NAS devices up before. The advice Dlink has on their website for Mac users connecting to the device is for the last version of OS X. But in a nutshell, in Finder, click on 'Go', then 'Connect to Server' and enter 'smb://" and after the // enter the IP address your router has assigned the device. Unlike other NAS devices, this one requires network know-how in that you'll need to setup User/Group permissions whereas some NAS devices give you a pretty GUI which hides this a little, but once you've set it up its a great little network drive. Once I need a couple more TB's, I'll be getting another one.