Back in April I was having a problem with my Thecus N4100 Pro where it was taking a long time to boot up, I’m talking around 8 hours or so. The confusing part was that on the display, it said it was ready, even though it hadn’t moved to displaying status information yet, and when I attempted to login via the web interface it would just hang until it had finished booting up properly.
I could not find anything on the net about it, and I couldn’t get any response from Thecus as to what the cause might be either.
I was doing some research into RAID arrays to try and find out how complicated it would be to move a RAID 5 array to a different RAID controller without rebuilding it when I was reminded that when one disk fails ina RAID 5 array, even though it will continue to function, it will be slower as the data needs to be rebuilt.
This prompted me to have a look at the RAID health through the web interface. It is meant to display on the N4100 Pro LCD if there is a problem with the RAID health however I couldn’t easily see the LCD from where I had it at the time. Unfortunately it was quite slow going accessing the web interface given how slow the NAS was performing in general. When I eventually got it open I discovered that one of the drives had indeed failed.
From what I understood from both the manual and my research online, replacing a drive in the NAS is as simple as pulling out the faulty drive and sliding in a new one. It should then automatically rebuild the data onto the new drive.
This was not the case however. The data simply would not be rebuilt automatically. I read numerous reviews on rebuilding and not one gave any extra steps, they all simply referred to it as simple and painless and only explained having to replace the drive.
The thing that none of them mention though is that after you replace the drive, you MUST set the new drive as a spare before the data will be automatically rebuilt. Once it is set as a spare, it will rebuild the data automatically.
So without further ado, here are some screen shots to help explain:
As can be seen in the screen shot above, you need to check the “Spare” check box and then click apply. This tells the NAS that this drive is a spare to be used to rebuild data onto when a drive in the array fails. As a drive has already failed, the NAS will automatically rebuild data onto the drive we have now set as a spare.
In the screen shot above you can see the NAS is now rebuilding the data onto the spare drive.
It really is very simple, the problem is both the manual and all of the instructions I could find online simply don’t mention the fact that the drive has to be a spare before the automatic rebuilding will occur.
What gave me the idea to try this was actually a review of one of the higher end Thecus NAS devices that indicated using the spare option to create a 3 disk RAID 5 array with a hot spare so that it would automatically rebuild immediately without needing to replace the drive, thus giving an extra level of redundancy and additional time to replace the dead drive.
Unfortunately I don’t have the address of the review anymore, but that’s it, it really is very simple once you know about the “Spare” check box.