Mac OS File Synchronization Software
File Synchronization Software allows one to sync files between two folders, disks or computers.
Synchronization is similar to backup software, but differs in that it allows copies both ways: the changes may have occurred on either side, while backup software always has a master side, which overrides the backup side. For backup software features like roll-back, historic archiving and the ability to make off-site backups (or previously: burn to DVD) are important. For synchronization software important features are the ability to detect which side has the latest version (e.g, if a file occurs on one side, it may either mean the file was created on that side, or that it was deleted on the other side, and the software needs to detect the difference), and graciously handle conflicts (e.g. when a file is changed on both sides).
Contents
List of Software
Synchronization Software
Here are the main Synchronization software programs for the Mac, roughly in order or recommendation.
| Application | Producer | Price | Notable features |
|---|---|---|---|
| ChronoSync | econ technologies | $40 (+$10) | Flexible and powerful, for $10 adds custom remote backup protocol |
| Synk | Decimus | $40 | Flexible and powerful, allows live synchronization |
| Synk Pro | Decimus | $60 | Flexible and powerful, allows live synchronization |
| FoldersSynchronizer | softoBe | $40 | Flexible and powerful |
| Synchronize X Plus | Qdea | $30 | Basic synchronization, does not retain permissions |
| Synchronize X Pro | Qdea | $100 | Flexible and powerful |
| GoodSync for Mac | GoodSync | $40 | Feels very Windows-based |
| DropBox | DropBox | varies | Stores your data in the cloud, you pay a yearly fee for the amount of data you store. |
For more option, I recommend Joe Kissell's Review of nearly 100 Mac backup apps. While not all information is complete, it does give a good set of criteria to check for.
Backup Software
If you're mostly interested in simple backup software, SuperDuper ($28) or Carbon Copy Cloner (donationware) are good choices.
Comparison of Synchronize, Synk and ChronoSync
I did some extensive testing of Synchronize, Synk and ChronoSync.
Common Features
All software above has the ability to auto-mount Apple File Shares (AFP). A disadvantage of synchronisation over a Apple File Share is that the AFP protocol does not support extended permissions (ACL), and that it may be slow if you have lots of files to check. ChronoSync and Synk solve this problem by optionally allowing synchronisation using a control daemon on the remote host, and using their own protocol.
ChronoSync
- Pro
- Detects metadata changes, displays metadata, Optional own protocol for $10 more
- Con
- No live sync
Synk
- Pro
- Live sync, Optional own protocol
- Con
- CPU intensive, can not exclude folders, does not detect metadata changes (though it is copied if the file is changed)
Synk Pro
- Pro
- Live sync, Optional own protocol, N-way sync
- Con
- CPU intensive, does not detect metadata changes (though it is copied if the file is changed), slightly less intuitive user interface
Synchronize Plus
- Pro
- Very easy to use preview window, displays size to copy, take per-folder or per-file based actions
- Con
- Does not retain basic metadata (file permissions), No live sync
Synchronize Pro
- Pro
- Very easy to use preview window, displays size to copy, take per-folder or per-file based actions
- Con
- Expensive, No live sync, does not detect metadata changes (though it is copied if the file is changed)
Conclussion
My recommendation is to buy Synk Pro if you like live synchronization, or ChronoSync if metadata means a lot to you. Synchronize Pro is a good (but more expansive) choice if you often like to preview the copy and delete actions. I would not recommend Synchronize Plus because it does not copy any metadata. In my case, all copies files ended up as world-writable. Not a great choice for your precious backups.
Synchronization software test
This test specifically targets synchronization software, not backup software, were features like roll-back, historic archiving and the ability to burn things on CD/DVD/Tape are much more important. Some application listed here may be unfit for synchronization purposes, but may be fit for backup purposes.
Interoperability with other synchronization application not tested.Some synchronization applications will first create a database with properties of the files, so they can keep track what has been changed without the need to compare it with an other share. This technique makes it easier to create more intelligent synchronization software, but typically does not work with other synchronization software and requires you to create such a database the first time you run it.
The answer are numbered according to the level of support it has for the listed feature:
| 11-19 | feature is not supported at all |
| 21-29 | very limited support of this feature |
| 31-39 | supports this feature |
| 41-49 | has outstanding supports for this feature |
Synchronization application basic tests
1) Two-way sync: adding files to two clean shares
11. no, all files are synced again, even duplicates 12. no, only one file is copied 31. yes, both new files are copied
2) Handles basic deletion: deleting file at each share
11. no, two files are added 12. no, one file is deleted, one is added 13. no, nothing happens 31. yes, the two files are deleted
3) Handles multiple computers
- make 3 shares with file1, file2, using synchronization app. - Delete file2 & add file3 at share 1. - Synchronize share2 & share3. (to possibly confuse last sync times) - Synchronize share1 & share2. - Synchronize share2 & share3. 11. no, three shares are not equal now 12. no, three shares are equal, but not correct 41. yes, three shares all have file1 & file3 only.
4) Handles conflicts: file modified on both ends
21. no, just overwrites the oldest one 22. no, just overwrites the smallest one 23. no, just overwrites the second one 24. yes, logs alert and does not copy (cron mode) 31. yes, always ask (user intervention required) 32. yes, always copies file to special location 41. yes, can be specified 42. yes, can be specified differently for cron & UI
Synchronization application intelligence tests
11) Smart time-state support: checks modification date, files size and md5 checksum
21. no, only checks file modification date only (not size) 22. no, checks file size only 31. yes, checks modification date and size 32. yes, allow user to choose between size and/or modification date 41. yes, checks checksum only 42. yes, checks modification date and checksum 43. yes, allow user to choose between modification date, size and/or checksum
12) Handles file renaming: file remains in folder, but is renamed
11. no, file is copied both ways 21. no, file is copied, old filename is deleted 41. yes, file is renamed (checks inode)
13) Handles folder renaming: only name of a folder is changed
11. no, folder with contents is copied both ways 21. no, folder with contents is copied, old folder is deleted 41. yes, folder is renamed (checks inode)
14) Incremental copies
11. No, always copies whole archive 31. yes, only copies changed files 41. yes, only copies the part of the file that was changed
Metadata preservation
12) Metadata change detection
11. No, only detects changes in file contents 12. No, only detects changes in file modification time 31. Yes, detects changes in permissions 41. Yes, detect changes in ACL, or extended attributes
21) Retain Permissions and Ownership
11. no, can only run as user, and does not preserve permissions 21. no, can run as root, but new files are made root 22. no, can only run as user, but preserves permissions 23. no, must run as root in GUI to handle this 24. yes, always asks for manual input of password 31. yes, must run as root in cron script to handle this 41. yes, asks for manual input of password, only if needed 42. yes, remembers password
22) Retain Access Control Permissions (e.g. chmod +a "_www allow delete" acl_file; ls -le)
(Note: AFP does not support ACL, so an application would need it's own protocol to copy these) 11. no, ACL is not copied 31. yes, ACL is copied if the file is copied 41. yes, ACL changes are detected and copied, even if the file itself is not changed
23) Retain HFS+ Attributes (e.g. SetFile -a V hidden_folder; GetFileInfo hidden_folder)
11. no, attributes are not copied 31. yes, attributes are copied if the file is copied 41. yes, attribute changes are detected and copied, even if the file itself is not changed
24) Retain Extended Attributes (e.g. xattr -w org.example.test some_value attribute_file; xattr attribute_file)
11. no, Extended Attributes are not copied 31. yes, Extended Attributes are copied if the file is copied 41. yes, Extended Attributes changes are detected and copied, even if the file itself is not changed
Filtering
31) Can exclude files or folders
21. no 22. yes, by full folder names only 23. yes, by full file names only 31. yes, by folder OR file only with pattern match 32. yes, by full folder and file names 41. yes, by files per folder 42. yes, by folder/file with pattern match 43. yes, by folder/file and regexp per folder
32) Can copy hidden files
22. no 31. yes, always 41. yes, configurable
Preview
31) Has preview option
no, always immediately synchronizes yes, optional preview shows all files yes, optional preview shows all actions (copy / delete / skip)
32) Folder view
11 no, shows only file individually 21 yes, shows files in collapsable folder 31 yes, shows folders, include a per-folder summary of the amount of data to copy 41 yes, shows folders, include a per-folder detailed summary of actions to take
33) Preview actions
22. yes, has preview, but cannot change anything 31. yes, has preview and can skip items 32. yes, has preview and can skip items once or permanently 41. yes, has preview and can change synchronization direction
34) Folder actions
11 no, shows only files individually 21 yes, acknowledge all proposed actions per folder 22 yes, shows folders, and can change copy direction, ignoring deletes 31 yes, shows folders, and can change synchronization direction, including deletes 41. yes, can take all actions based on folder or multi-line selections
Automated Backups
41) Can make schedules
11. no 12 no, but you can write a custom Launch script yourself 21. no, preview window always need to be confirmed, even if there are no conflicts 22. yes, only if application is not closed 31. yes, the application automatically starts at the scheduled time 41. yes, a daemon is tracking changes while you make them (live synchronization)
42) Advanced Scheduling options
11. no, only manual scheduling 12. no, only able to schedule per day/week 13. no, will cancel scan if computer is off, instead of postponing them 21. yes, can schedule per weekday 31. yes, can postpose scan based on user activity 32. yes, can postpose scan based on open application 33. yes, can postpose scan based on network settings 41. yes, can postpose scan based on all above settings
43) Can run in background
11. no, requires user interaction 22. no, pops up, but can easily be clicked away 31. yes, no feedback at all 41. yes, visible, non intrusive (e.g. menu bar or background)
44) Auto Mounts/unmounts disks
11. no 21. yes, only mount, never unmounts 32. yes, mount and always unmounts 41. yes, mount and unmount only if disk was not mounted before
45) Custom sync protocol
11. no 31. yes, faster than AFP sync 32. yes, more secure than AFP sync 41. yes, better metadata support than AFP sync
46) Archive deleted files
21. no, files are always deleted without recoverability 21. no, files are moved to trash; doesn't work for network disks 31. yes, files are always moved to special folder 41. yes, files are optionally moved to special folder 42. yes, files are moved to special folder, and there is an easy recovery tool
Synchronization application speed tests
51) Local Transfer speed test (little files, lots to copy)
- Two empty shares. Add 100 files of 1 MB to one share. measure time. - Local connection
51) Remote Transfer speed test (little files, lots to copy)
- Two empty shares. Add 100 files of 1 MB to one share. measure time. - Remote connection
52) Transfer speed test (little files, lots to copy)
- Two empty shares. Add 1000 files of 100 kB to one share. measure time. - Remote connection
53) Query speed test (lots of files, little to copy)
- Two shares with 5000 files of 20 kByte. Only 1 is changed. measure time. - Local connection
