6. RAID

One of the main features that attracted me to this box was its support for RAID. Three different modes are supported: Just a Bunch Of Disks (JBOD), RAID level 0, and RAID level 1. JBOD allows you to treat the two internal drives as a single larger unit, but offers no additional data security or performance. RAID level 0 increases performance by splitting data storage and I/O across the two drives, but provides no increased security. RAID level 1 increases data security by mirroring data on the two internal drives, and also increases read performance since the two drives can be read independently. The main drawback is that the total disk capacity is cut in half (since each drive contains a copy of the same data). I was interested in data security, so I went with level 1. Figure 9 shows the RAID configuration screen.

Figure 9: RAID Configuration Screen

One of the things I wanted to check in the device was its RAID failover capability. To test this, I simulated a drive failure by shutting the system down, unplugging one of the two internal drives and booting it back up. When the box was coming up, I expected to see some sort of flashing error indicator, but if there was one, I missed it. When the system was back up, I was able to mount the shares I had defined previously, and everything appeared to be in place. A check of the status log gave me a single message:

RAID status is DEGRADED now

I also had hoped to get an email indicator of the issue, but I never received any. This is why it would have been nice to have a test button for setting up email notices. I couldn't tell if the email was never sent, or if email notification just wasn't working.

To see if I could recover from the problem, I shut down, replaced the drive and powered back up. When the system booted, however, it was still running in a "degraded" mode. Not until I went into the RAID configuration page and manually recreated the RAID mirror did it start to recover. During the recovery phase, the system was still usable and my data was available. The status page showed the N2100 CPU usage jump to as high as 75%, but it was more commonly under 15%; the system would probably be a bit sluggish during this phase. Total recovery time for my 80 GB drive was just over an hour.