I have a data array of 10 drives (xfs) and a small ssd for a half-empty cache (btrfs), in a Pro system running 6.9.2 as a recent upgrade from 6.3.5.  For now I have all data except appdata and docker.image written only to the data arrays.  My docker apps all point to /mnt/cache/appdata (though some now unused dockers had pointed to /mnt/user/appdata in error).  

 

For some reason I can't understand the contents of /mnt/cache/ show up also in /mnt/user/, though of course /mnt/data/ has all of the other array data.  Regular data written to /mnt/user/Media don't get copied to cache, just appdata and docker.img.

 

 

I don't think I specified this mirror.  I checked and they aren't soft links to each other, and at least for the similarly mirrored docker.img the inum of the files in the two locations are different, so they're not hardlinked.  If I create a junk directory in one it shows up instantly and if disappears if I delete its twin.

 

It feels like data is written to both cache and array at the same time, but I *think* I have not set the cache behavior this way.  On the other hand I can't see right now how to tell the cache drive in the webGUI how to behave.  The shares are all 'array only' at present or 'prefer cache'.  I have mover set to move monthly but since data isn't currently being written to the cache it isn't moving much. 

 

Can anyone see where I might have specified this behavior?    I don't want it since it likely slows down the cache to have to write to the array as well, and it consumes 100GB+ of array needlessly.

 

Thanks in advance

You do NOT have the files mirrored - they are simply different views of the same files.

 

Usef Shares provide an aggravated view of files within a top level folder on all array and pool drives. You might want to read the online documentations accessible via the ‘Manual’ link at the bottom of the GUI to find out more.

Thank you;  it makes sense now.  For others stumbling across this here is what I learned.

 

/mnt/cache  is data actually on the cache drive(s)/pool

/mnt/user0 (now deprecated, but I think valuable) is data actually on the array drives

/mnt/user is a logical summation of data on both cache pool and data array

 

The recommended way of moving data between cache and array is to specify preferences in shares and then to invoke the Mover.

 

I of course understood that regular data files written to /mnt/user behaved like that when the cache pool is used for writing new data, I just thought that writing to /mnt/cache was different.  I actually found a 0 byte file in /mnt/user0/appdata that is not in /mnt/cache/appdata 🙃 so managed to clean appdata up after all.

 

Thanks again