4. Advanced Options, Continued

Under the "Backup" tab, I found an option to backup and restore other network shares. The idea is to export disks or directories on your computers, then configure the Yellow Machine to back them up. These backup jobs could be scheduled for certain times, or performed manually. The short functionality test I ran backed up my KuroBox just fine. Figure 8 shows the Yellow Machine screen where backup options are presented.

Figure 8: Yellow Machine backup options screen

Because the Yellow Machine is a RAID capable device, there is also a menu to configure or check status of its four internal drives. The device supports RAID Levels 0, 1, 1+0, and 5 (it's configured at RAID Level 5 by default). These options are depicted in Figure 9, which shows the default setting.

Figure 9: Yellow Machine RAID options

To try out the Yellow Machine's RAID capabilities, I conducted a small informal test. While playing a movie from a network mounted share, I removed the cover and yanked the power cable from one of its disk drives. The box kept humming along and the movie didn't skip a beat. I expected to see a "Fault" LED turn on, but it didn't and I could detect no difference in behavior. Several minutes later I received an email notifying me of a failure on disk2 and a check on the status sceen showed that one disk was "faulty".

Next I rebooted the box. When it came back up, I could still see no difference in behavior, and there was still no "fault" LED. The status screen now just showed that there were only three drives present. Next I shut the box down, reconnected the drive power cable and rebooted. This time the status screen again showed a faulty drive. There didn't appear to be any automatic recovery going on, so I went into the RAID setup screen and told it to repair the drive. This recovery was completed in a few seconds and the status screen showed everything as normal. However, even though everything was listed as normal, from the flashing LEDs and the noise of the disk drives, it was obvious that the repair was continuing on in the background.

A subsequent status email revealed more specifics. Embedded among all of the other information, the following text appeared:
     md: minimum _guaranteed_ reconstruction speed: 100 kB/sec/disc.
     md: using maximum available idle IO bandwith (but not more than 100000 kB/sec) for reconstruction.

This appeared to indicate that although the repair would proceed in the background, it would not consume all available disk bandwidth. To verify this, I fired my movie up again and watched it without a glitch. My experiment demonstrates convincingly why RAID systems are important for data preservation: You can lose an entire hard drive yet still not lose any data.

I also browsed through other menus and found an interesting omission - there was no ability to create new shares! Though a single network disk share was predefined, I could find no menus or options to create another.