Synk Help
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# When can I use ZeroScan?

In order for ZeroScan to function properly, it must know about every change that is made to files. If a file is changed without ZeroScan being notified, Synk will never look at that file and its new contents will never be backed up.

The Synk Helper provides the base functionality for ZeroScan. Once running, it receives notifications of every filesystem event that occurs on the computer on which it is running. Thus, in order for ZeroScan to work properly, every filesystem event pertinent to your script must pass through your computer.

This can be confusing, so here are some examples:

## Example 1: Basic backup to external hard drive

Situation: You work on your machine only, and back up to an external hard drive.

Verdict: ZeroScan can be used in this situation. Every change to your data is through your computer, where the Synk Helper will be running.

## Example 2: Basic backup to remote server

Situation: You work on your machine only. However, the destination of your backup is a remote server--say, .Mac.

Verdict: ZeroScan can be used in this situation. Every change to your data is through your computer, where the Synk Helper will be running. Even though a remote server is involved, the backup files aren't changed by anybody else--only through your computer.

## Example 3: Synchronizing two machines

Situation: You have two machines and use Synk to keep your Documents folder in synch on both machines.

Verdict: ZeroScan cannot be used in this situation. Changes to the second machine do not pass through the first machine, where the Synk Helper is running. Even if another copy of the Synk Helper were running on the second machine, this would not change the result--neither copy of Synk Helper has the whole picture in one place.

## Example 4: Server backups

Situation: You have a central server which many users connect to and change files in file-shared volumes. You back this server up to an external location.

Verdict: ZeroScan can be used in this situation. Even though the changes originate on many remote machines, they all pass through your server, which actually performs the changes.

## Example 5: Using a USB key "shuttle"

Situation: You have two machines (at work and home), and use Synk on both machines to synchronize with a USB key which you carry between them.

Verdict: ZeroScan cannot be used in this situation. Each machine is carrying out an independent synchronization with the USB key, and neither machine's Helper can see the changes made to the key on the other machine.

## See also

ZeroScan