Over the past couple of weeks, I have been working with a school on getting a 2GHz Xserve G5 up and running to replace a PowerMac G5 operating as a server. The Xserve had no memory so we acquired 4GB of memory. In early 2011, I had upgraded the PowerMac G5 to dual Western Digital WD2003FYYS 2TB drives in a RAID 1 configuration.<! data-preserve-html-node="true"--more-->

All of this had been working perfectly but then the Xserve G5 was donated to the school and it was time to move the drives. After the memory arrived I installed it and attempted to just move the drives over. I had also initially setup the RAID 1 using SoftRAID (an excellent product by the way).

When I attempted to boot the Xserve with the 2TB drives, it just refused to boot and flashed the infamous folder error meaning it cannot find a boot drive. Although unlikely, I thought perhaps SoftRAID was preventing the drives from booting in the Xserve G5 and so I used SoftRAID to convert the on-disk format to Apple RAID.

I was also unable to boot from the Mac OS X 10.5 boot DVD. After some additional research, it occurred to me that the Xserve only had a CD drive and not a DVD drive. With that discovery, I decided to create a bootable FireWire drive with Mac OS X 10.5.8 as a means of booting the system.

Using the FireWire drive worked perfectly and allowed me to boot the system and get a better idea of what could be keeping the 2TB drives from being recognized. Oddly, one of the 2TB drives would finally mount in the Xserve after a considerable delay but the second drive would only mount after a long wait and only once in every ten reboots or so. If the second drive ever mounted, its paritions would never be properly recognized as part of a RAID set.

I started digging for more information about what could be causing this very strange behavior. Contrary to what some other users experienced, the drive trays did not show an orange light but instead showed a normal green light but only one drive would show any activity as indicated by the blue light.

After some searching and a great deal of trial and error, I came across a post on the Apple discussion forums detailing how another user had the very same WD2003FYYS drives and was able to get them to work perfectly by putting a jumper on pins 5 and 6 which causes the drive to only operate at 1.5Gb/s instead of the typical SATA II speed of 3.0Gb/s.

Once I set these jumpers, the drives came right up. Both RAID sets showed as degraded even though each RAID set had two partitions as expected. Disk Utility showed no further information so I moved to the Terminal. I ran:

diskutil listRAID

The output showed me that each RAID set had three partitions and one was marked as missing. I used the following command to remove the extra parition:

diskutil removeFromRAID (replace with missing partition's UUID) disk3

Obviously "replace with partition's UUID" refers to the UUID of the extra partition. The RAID set itself will also have a disk reference such as disk3, disk4, etc. In this case, both disk3 and disk4 are RAID sets made up of two partitions, one from each 2TB drive. This allows a separate boot RAID set and data RAID set.

Once I had removed the extra partitions from each set, the RAID sets immediately changed to online from the previous degraded state. This whole process was more complex than I expected but finally works as expected.

If you are facing a similar upgrade, I have read in a variety of posts that Seagate drives seem to work without issues while Western Digital drives tend to require the 1.5Gb/s jumper workaround. Hopefully I will not run into this exact problem again, but if I do, it should be an easy fix.