I'm just getting everything setup with unRaid 6 and trying to figure out which format would be best for my cache disk. I'm just using a fairly straight forward media server. I plan to install a few Dockers (Plex, OpenVPN possibly, maybe a couple of others). I'm not sure if a cache pool would be necessary since I don't know how large to expect these Docker images to be, but it appears that it might be easier to setup later if the original disk is already formatted to BTRFS. I haven't been able to find any sort of How-To for this though. I have seen quite a few posts that XFS is a more stable file system and that BTRFS is subject to corruption, but I'm not sure if these statements are still true with v6.0.1?

 

Any advice/opinions welcome.

I'm just getting everything setup with unRaid 6 and trying to figure out which format would be best for my cache disk. I'm just using a fairly straight forward media server. I plan to install a few Dockers (Plex, OpenVPN possibly, maybe a couple of others). I'm not sure if a cache pool would be necessary since I don't know how large to expect these Docker images to be, but it appears that it might be easier to setup later if the original disk is already formatted to BTRFS. I haven't been able to find any sort of How-To for this though. I have seen quite a few posts that XFS is a more stable file system and that BTRFS is subject to corruption, but I'm not sure if these statements are still true with v6.0.1?

 

Any advice/opinions welcome.

The BTRFS decision is irrelevant as far as Dockers are concerned.  Dockers are stored in a file that is treated as a disk image.  Although this image is internally formatted with BTRFS, it does not matter what format the drive hosting it is using.

 

The main reason for going with BTRFS would be if you want to move to having a cache pool (i.e. more than one drive in the cache) to give the cache resilience against drive failure.  That is only available when the cache uses BTRFS format.  If you are not going to ever use that feature then XFS is probably the most robust answer.

My personal advice is avoid BTRFS if you can. XFS works fine for a single cache drive. The docker.img will run Btrfs internally so Dockers will function on top of any filesystem.

So the cache pool isn't about increasing the capacity of the cache, but rather protecting the data? I guess maybe my question should have been more along the lines of how big a cache do I need? I don't have any experience with Dockers and no idea how large to expect the images to be. I currently have a 1TB drive installed as Cache. It's always been plenty big enough to accommodate file transfers, but I'm not sure once I start adding Dockers?

Personally, I had serious "slow down" issues with using a BTRFS cache.  Since switching to XFS, I have had zero issues.  I just make sure it gets backed up properly.

So the cache pool isn't about increasing the capacity of the cache, but rather protecting the data? I guess maybe my question should have been more along the lines of how big a cache do I need? I don't have any experience with Dockers and no idea how large to expect the images to be. I currently have a 1TB drive installed as Cache. It's always been plenty big enough to accommodate file transfers, but I'm not sure once I start adding Dockers?

Dockers themselves will not take up much space.  A size of 10-20gb seems typical.  All that is held in the docker image file are the binaries relating to docker - any configuration files or workspace is external to the docker image file.  What is likely to be of more concern is any workspace the applications that you intend to run under Docker need.  Without knowing what applications they might be it is impossible to guess.