Who and why needs it? (nonraid or unraid, whatever)

[Kamillaova]

[qvr]

I think this HN comment gives a good overview of how unraid differs from traditional raid implementations:

md takes multiple partitions to make a virtual device you can put a file system on, with striping and traditional RAID levels
unRaid takes multiple partitions, dedicates one or two of them to parity, and hands the other partitions through. You can handle those normally, putting different file systems on different partitions in the same array and treating them as completely separate file systems that happen to be protected by the same parity drives

This enables you to easily mix drives of different sizes (as long as the parity drives are at least as large as the largest data partition), add, remove or upgrade drives with relative ease, and means that every read operation only goes to one drive, and writes to that drive plus the parity drives. Depending on how you organize your files you can have drives that are basically never on, while in an md array every drive is used for basically every read or write.

The disadvantages are that you lose out on the performance advantages of a RAID, and that the raid only really protects against losing entire disks. You can't easily repair single blocks the way a zfs RAID could. Also you have a number of file systems you have to balance (which unRaid helps you with, but I don't know how much of that is in this module)

As for who and why of this project itself, at this stage it is for advanced DIY enthusiasts who want to try out the array tech without all the bells and whistles the commercial unRAID OS provides.