If a share is set to "Prefer" cache, why would data appear on more than one disk in the share?

[arretx]

When I look at my shares, and I click on /appdata, it shows that the contents are found on both `cache` and `disk5`.

 

The /appdata share is set to Prefer cache, which would make me think that all of the important appdata files are actually on the cache disk.  When I look at the contents of cache and disk5, I see nearly identical files and folders.

 

There may have been, at one point, where, due to the potential failure of my cache pool, I changed all of my Prefer shares to Yes to force the mover to move the files off of the cache temporarily.

 

The setting "Prefer" states that "Mover transfers files from array to cache" and "Yes" is the opposite, "Mover transfers files from cache to array."

 

Under what circumstance might I have inadvertently duplicated content in the array that no longer needs to be there because it has been "moved" back to the cache?  Are we actually moving files, or are we copying files when we employ the Cache settings?

 

Thanks!

[itimpi]

4 hours ago, arretx said:

Under what circumstance might I have inadvertently duplicated content in the array that no longer needs to be there because it has been "moved" back to the cache?  Are we actually moving files, or are we copying files when we employ the Cache settings?

If you had a cache drive failure then appdata would have started being written to the array so this is where you might get files on the array.  Mover will also never move open files so you may need to to temporarily disable the docker (and VM) services to allow mover to take action on files that would otherwise be open.

 

The other point that is relevant is that mover never overwrites an existing file so if the same file exists on both the pool and the array then no action is taken.   It is then up to you to remove the copy that is not wanted.  Typically this would be the copy on the array as if both exist the pool copy takes precedence but you have to make that determination.