Performance Benefits / Drawbacks of BTRFS RAID10 vs 2x BTRFS RAID1 cache pools?

[SimplifyAndAddCoffee]

Hi,

 

I am trying to decide how to manage the cache drives on my new server.  I have 4x 1TB SSDs which I intend to use for protected cache. I have one or more shares which will need a very large cache pool for storing downloads on their way to the array, and also docker images and appdata which will be used regularly.

 

I had planned initially to use 2 pools of 2x 1TB SSDs each in BTRFS RAID1, and use one for caching the downloads and other shares, and one for docker, system, and appdata... however I am now wondering if I might be better served using a single BTRFS RAID10 pool for all of them, in order to fully utilize all of the available drive space. 

 

Apart from the obvious benefit of being able to use more of the 2TB of space for caching downloads etc when the docker/appdata folders are small, I want to address some concerns about the performance of the pools for caching in BTRFS RAID1 vs RAID10 mode, and fault tolerance.

 

Am I asking for trouble using BTRFS RAID10? Is there a significantly greater chance of data loss or downtime from drive failure?

 

Does RAID10 offer a clear performance benefit over RAID1 (outside of that which can be gained by splitting competing services to different pools)?

 

with BTRFS RAID1 will the RAID remain software and hardware agnostic? e.g., can you read from a single disk without the array, like you can with the UNRAID array?

 

Conversely, with BTRFS RAID10, I would assume you cannot... but can you at least still rebuild the array without taking it offline?

 

Thanks in advance.

[JorgeB]

Btrfs raid10 is about as stable as raid1, but you could only lose 1 disk of 4, with dual raid pools you can lose 1 of 2, also if you lose one pool due to fs corruption or other issues you don't lose everything so for that is better, raid10 would have a nice performance bump, but in either case you should have backups.