partition-based parity rather than disk-based parity

[grana]

I've recently moved from QNAP to Unraid, and there is one thing that I'm missing. 

 

I guess all users have some high priority media / documents that want to be as safe as possible, and some other content that has lower priority. Say for example I have a Windows VM; I probably care a lot about the content of the VM itself, or the configuration, but the original ISO downloaded from microsoft.com? Not so much. I don't really need those x GB to be duplicated or even triplicated.

 

As a noob user (I purchased the license yesterday, after 15 days of evaluation) what I am doing is having 2 disks in my array (1 + 1 parity), and another disk as pool device. Then, for example, all my docker images are configured to have configurations stored on the array disk (`/mnt/user`), but the scrap files on `/mnt/my_pool_disk`. Does it make sense?

 

Now, to QNAP. QNAP has this nice feature where you can

1. partition the disk. Partitions are not fixed size, but they can grow or shrink based on the content.

2. for each partition, decide what cloning / redundancy strategy you want to adopt, and where the data should be cloned to (ie, one disk to another).

 

Why does it matter? Well, it's simple. Say I have 3 disks, 4 TB each. The files I want to keep with parity are 500 GB. 

With QNAP, my total available storage is going to be 4 TB + 4 TB + 4 TB - 500 GB = 11.5 TB (500 GB of "wasted" duplicated storage). With Unraid my total storage is 8 TB (one parity disk, one disk in the array, one outside the array (or both of them into the array)).

 

Basically, it would no longer be a parity disk, but a parity partition, calculating parity bits for a subset of the partitions on the disks.

 

Thanks and keep up the great work