View source for Mac OS File Synchronization Software

{{Outdated|October 2005|March 2012}}

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).

==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
|-
| [http://www.econtechnologies.com/pages/cs/chrono_overview.html ChronoSync] || econ technologies || $40 (+$10) || Flexible and powerful, for $10 adds custom remote backup protocol
|-
| [http://www.decimus.net/Synk Synk] || Decimus || $40 || Flexible and powerful, allows live synchronization
|-
| [http://www.decimus.net/Synk/SynkPro.html Synk Pro] || Decimus || $60 || Flexible and powerful, allows live synchronization
|-
| [http://www.softobe.com/products/flsy/pp.html FoldersSynchronizer] || softoBe || $40 || Flexible and powerful
|-
| [http://www.qdea.com/synchronize_x_plus_intro.html Synchronize X Plus] || Qdea || $30 || Basic synchronization, does not retain permissions
|-
| [http://www.qdea.com/synchronize_pro_x_intro.html Synchronize X Pro] || Qdea || $100 || Flexible and powerful
|-
| [http://www.goodsync.com/mac GoodSync for Mac] || GoodSync || $40 || Feels very Windows-based
|-
| [http://www.dropbox.com/ 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 [http://www.takecontrolbooks.com/resources/0014/ 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, 
[http://www.shirt-pocket.com/SuperDuper/ SuperDuper] ($28) or [http://www.bombich.com/ 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===

==== Test 1. Two-way sync: adding files to two clean shares ====

{|
! My Score !! Possible result
|-
| 11 || no, all files are synced again, even duplicates
|-
| 12 || no, only one file is copied
|-
| 31 || yes, both new files are copied
|}

==== Test 2. Handles basic deletion: deleting file at each share ====

{|
! My Score !! Possible result
|-
| 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
|}

==== Test 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.

{|
! My Score !! Possible result
|-
| 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.
|}

==== Test 4.  Handles conflicts: file modified on both ends ====

{|
! My Score !! Possible result
|-
| 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===

==== Test 11.  Smart time-state support: checks modification date, files size and md5 checksum ====

{|
! My Score !! Possible result
|-
| 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
|}

==== Test 12.  Handles file renaming: file remains in folder, but is renamed ====

{|
! My Score !! Possible result
|-
| 11 || no, file is copied both ways
|-
| 21 || no, file is copied, old filename is deleted
|-
| 41 || yes, file is renamed (checks inode)
|}

==== Test 13.  Handles folder renaming: only name of a folder is changed ====

{|
! My Score !! Possible result
|-
| 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)
|}

==== Test 14.  Incremental copies ====

{|
! My Score !! Possible result
|-
| 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===

==== Test 12.  Metadata change detection ====

{|
! My Score !! Possible result
|-
| 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
|}

==== Test 21.  Retain Permissions and Ownership ====

{|
! My Score !! Possible result
|-
| 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
|}

==== Test 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)

{|
! My Score !! Possible result
|-
| 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
|}

==== Test 23.  Retain HFS+ Attributes (e.g. SetFile -a V hidden_folder; GetFileInfo hidden_folder) ====

{|
! My Score !! Possible result
|-
| 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
|}

==== Test 24.  Retain Extended Attributes (e.g. xattr -w org.example.test some_value attribute_file; xattr attribute_file) ====

{|
! My Score !! Possible result
|-
| 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===

==== Test 31.  Can exclude files or folders ====

{|
! My Score !! Possible result
|-
| 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
|}

==== Test 32.  Can copy hidden files ====

{|
! My Score !! Possible result
|-
| 22 || no
|-
| 31 || yes, always
|-
| 41 || yes, configurable
|}

===Preview===

==== Test 31.  Has preview option ====

{|
! My Score !! Possible result
|-
| 11 || no, always immediately synchronizes
|-
| 21 || yes, optional preview shows all files
|-
| 41 || yes, optional preview shows all actions (copy / delete / skip)
|}

==== Test 32.  Folder view ====

{|
! My Score !! Possible result
|-
| 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
|}

==== Test 33.  Preview actions ====

{|
! My Score !! Possible result
|-
| 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
|}

==== Test 34.  Folder actions ====

{|
! My Score !! Possible result
|-
| 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===

==== Test 41.  Can make schedules ====

{|
! My Score !! Possible result
|-
| 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)
|}

==== Test 42.  Advanced Scheduling options ====

{|
! My Score !! Possible result
|-
| 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
|}

==== Test 43.  Can run in background ====

{|
! My Score !! Possible result
|-
| 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)
|}

==== Test 44.  Auto Mounts/unmounts disks ====

{|
! My Score !! Possible result
|-
| 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
|}

==== Test 45.  Custom sync protocol ====

{|
! My Score !! Possible result
|-
| 11 || no
|-
| 31 || yes, faster than AFP sync
|-
| 32 || yes, more secure than AFP sync
|-
| 41 || yes, better metadata support than AFP sync
|}

==== Test 46.  Archive deleted files ====

{|
! My Score !! Possible result
|-
| 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===

==== Test 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

==== Test 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

==== Test 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

==== Test 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

[[Category:Comparison]]
[[Category:Software]]