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RAID Fail Test

One of the reasons you buy a two drive system is for the fault tolerance that RAID 1 provides. In order to test the Pro Duo's fault tolerance, we first re-formatted the array from RAID 0 to RAID 1. Of course, all data was wiped during this process. We then recreated a share and loaded about 9 GB of data to it.

In order to simulate a drive failure, we removed that combined SATA power/data cable from Disk 1. Our expectation was that the Pro Duo would give a visual indication of an error and continue working. That's not what happened. The Pro Duo did send out four emails indicating write errors as well as one indicating that it had entered degraded mode. Each of the emails recommended an immediate change of disk.

Then, the unexpected happened. The Pro Duo shut down. We attempted to reboot the device and it never came back online. At this point, the power switch didn't shut the device down, so we disconnected the power. We then reconnected the power/SATA cable to the drive (Disk 1) we had failed and rebooted.

The Pro Duo came back online and a third LED, located between the power and link/activity LEDs and not normally seen, started flashing red. Over the course of the next 13 minutes, a total of 9 emails were received. One indicated that the Pro Duo had entered degraded mode while the rest of them indicated the start and completion of what appeared to be various portions of the array. Here are two sample emails:

Email #1

RAID re-build notice
Target array:System field (md0) Target disk:Disk 1 RAID array re-build has started.
[LinkStationInformation]
LinkStationName: LS-WTGL005 (LS-WTGL/R1)
Time: 2008/01/30 08:22:36
Setting Screen: http://192.168.100.192/

Email #2

RAID re-build notice
Target array:System field (md0)
Target disk:Disk 1


RAID array re-build is complete.
[LinkStationInformation] LinkStationName: LS-WTGL005 (LS-WTGL/R1) Time: 2008/01/30 08:23:10 Setting Screen: http://192.168.100.192/

Though the emails stopped coming, the error condition LED was still blinking red, so we assumed that the device had not completely healed itself. It turns out that that was a correct assumption. When logging into the Pro Duo, the home page indicated a disk error. Clicking on the error message took us to the Disk Management page.

Disk Management page showing error
Click to enlarge image

Figure 12: Disk Management page showing error

We selected Disk 1 (Disk 2 was greyed out) and clicked on Restructure RAID Array. We received a warning that all data on the target disk was going to be deleted.

Restructure RAID Array warning message
Click to enlarge image

Figure 13: Restructure RAID Array warning message

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