What mirroring does

With mirroring on, a copy of each transferred file is stored so you can retrieve it later. Without it you have a record that a file moved — its name, size, and a fingerprint — but not the file itself.

When it matters

Mirroring turns a log into evidence. If a file leaves a machine and you need to know what was in it, mirroring is the only way to find out. It also lets you confirm a suspected leak rather than relying on an account of what happened.

• Each stored copy is fingerprinted, so you can confirm it is the file that moved.
• Stored copies follow your plan's retention period and storage limit.
• Very large files may be excluded to stay within the size limit.

Handling stored copies

Stored evidence can contain sensitive material, because that is the point of it. Treat it accordingly and delete transfers you no longer need to keep.