The Share Settings page contains up to three sections depending on whether user shares are enabled or not, and if enabled, whether a cache disk is present or not, and if present, whether the cache disk is enabled or not.
Min. Free space
The min free space defines the minimum free space there must be a disk assigned to the share before writing will be allowed to the share. If a cache disk is not present, the share can only be written if the defined min.free space is available on a disk.
If split level is defined, then beware that writing will be permitted to a disk with less than Min Free space available, if writing to a directory beyond the split limit. So if a folder has already been assigned to a specific disk due to a split level, then the min-free-space check is omitted. Hence with a Split level of 1, and no disks with min free space available and an overfilled cache disk (or no cache disk), ONLY writing to the root folder will cause a write error.
If a cache disk is present, and the cache disk is not overfilled, then the share will allow writing even though the share is overfilled thus ignoring the Min. Free space parameter defined here. However if the disks are filled beyond the Min. Free space limit then the mover process will fail to move files and the a syslog entry will be created saying roughly 'shfs/user: shfs_mkdir: assign_disk: media/4 (28) No space left on device'. (This min-free-space behaviour is present in unRaid v5b14 + v5.0rc5, maybe other versions behave differently).
Note that cache min free space limit is not entered in the this Settings page for Shares, but in the Settings > Share Settings page.
You enter a numeric value in this field, optionally followed by one of these suffixes: KB, MB, GB, or TB. If a suffix is omitted, then the value is taken to mean a count of 1024-byte blocks. Examples:
20GB => (20 Giga-Bytes, or 20,000,000,000 bytes).
20000000 => (20,000,000 disk blocks, or 20,480,000,000 bytes).
When user shares are enabled, you can specify which array disks(s) should be included (or excluded) for consideration by the user share file system. For example, to include only disk1, disk2, disk3 and disk5, set:
Included disk(s): disk1,disk2,disk3,disk5
Included disk(s): disk1-3,disk5
To include all array disks except disk4, set:
Excluded disk(s): disk4
Typically one would not fill in both fields.
When a cache disk is present it may be configured in the Cache Settings section.