SmallNetBuilder

RAID Fail Test

With my recent experience with the DNS-321's touchy RAID recovery, I wondered if the 343 would perform similarly. In short, it did... with a few other twists.

I first set up email alerts and found that they worked just like those on the 321. I would get short "drive failed" messages when I pulled a drive, but nothing indicating rebuild start or finish.

I started a long file copy and first pulled the top drive (#1). The only failure indication on the OLED panel was that the drive icon disappeared. Since the 343 doesn't have a beeper, I thought D-Link would have taken advantage of the screen and flashed a message to make it obvious that something was wrong. Unfortunately, they don't, so you need to be very observant to notice that something is amiss.

As with most NASes, the admin interface makes you go hunting to find a problem. But at least you can navigate right to the Status screen, which showed a proper Degraded status.

Since hot-swap isn't supported, I powered down the 343, plugged the "failed" drive back in and rebooted. But when I logged in, there was no warning of drive failure and I found that the Status screen still showed as degraded. So I navigated to the Tools > RAID screen to start the rebuild, but found only the option to Re-configure All Existing Hard Drive(s). Not good.

The 343's User Manual says that the 343 is supposed to prompt you to format a replacement drive. But, as with the 321, since I wasn't using an unformatted drive, it didn't recognize it and offer the option. Unfortunately, this time, I didn't have another SATA drive around, so couldn't test that it would be properly recognized and used to rebuild the array.

To be fair, this test doesn't simulate what happens in an actual failure (since you wouldn't be reinserting the same drive). But we run the same test on all RAID products and the D-Link NASes are the only products we've encountered that don't properly rebuild the array.

When I tested the 321, I found that failing the second drive caused a different behavior. So I had the 343 rebuild the array and then I pulled drive #3. But upon powering down, reinserting the drive and rebooting, I encountered the same "Re-configure All Existing Hard Drive(s)" option.

So I decided to have some fun and reinserted drive #3, didn't rebuild the array, started a file copy and pulled drive #4, forcing a second drive failure. To my surprise, the filecopy continued for about 10 seconds before Windows finally threw up the error box shown in Figure 6. It wasn't until after I shutdown and rebooted the 343 that the volume finally disappeared.

Figure 6: Filecopy error from a degraded volume

The 343 offers two options not present in the DNS-321. There is a Scan Disk option under the Maintenance menu and you can choose between EXT2 ("Best Performance" according to the D-Link selector) or EXT3 ("Most Stable") filesystems.