I’m not entirely sure why the default behavior with regard to RAID would be to fail on startup since the point of RAID is for a system to survive a drive failure. However, the default behavior for Ubuntu is for the system to fail if a RAID array is degraded at boot time. Not only will it fail to boot it will also fail to give any useful information and spend several minutes before delivering the user into a recovery console. A far more useful behavior would be to prompt for a number of seconds that an array is degraded and then continue to boot (with an option to reverse this behavior). In any case, this is not a difficult situation to remedy though finding the right information can be.

I thought there was an easier way to do this but perhaps I have forgotten. I am a fan of Linux software RAID because of the fact you can transport the drives to other systems without having to worry about hardware RAID compatibility. Linux software RAID 1 also possesses good performance and reliability. However, sometimes you need to repair file system damage or create an image of the filesystem or perform other tasks needing the arrays to be accessible from either a Live CD or from another system. Here’s how I accomplished this recently.

I suppose that growing a RAID 1 array is not very common but I had a client that wanted to go from a 2 disk array to a 3 disk array so that one disk could be rotated out periodically and kept off-site. Here were the steps:

• mdadm --add /dev/mdX /dev/sdXX
  • This adds the partition to the array as a hot spare.
• mdadm --grow /dev/mdX -n 3
  • This increases the number of disks from 2 to 3.

I’ve been doing a lot of research on storage solutions for a couple of projects. I’ve been delving into RAID setups for large numbers of disks and trying to determine in what situations a hardware RAID controller is appropriate instead of Linux software RAID. I’ve also been considering various nested RAID levels and their value.

For a while I’ve been considering that a SATA backplane would really make server work easier. But for an inexpensive server an inexpensive backplane is needed. I decided to look again tonight and see what I could find. I included 3-in-2 (3 3.5” drives in 2 5.25” bays), 4-in-3 (5 3.5” drives in 3 5.25” bays), and 5-in-3 (5 3.5” drives in 3 5.25” bays) models.