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What software can I use to synchronize files that detects changes on each of my computers and syncs continuously with an always-on server? I'm looking for:

  • Running as a service on the server and the clients
  • Realtime change detection
  • Delta sync (ID3 tag editing shouldn't result in the whole file being transfered, for example)

I have a VPN, so local network only and unencrypted traffic is OK. Services that require cloud storage like DropBox are out since I'm maintaining my own server.

EDIT: I've been using the excellent Cubby (in beta at https://www.cubby.com/). No need for a VPN, seems almost like the holy grail of sync. Online storage is optional, so you have uninhibited direct sync without it.

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Unison is a possibility, but it does not have actual change detection on Windows, only a "repeat every X seconds" mode. –  grawity Jan 7 '12 at 19:30
    
You could use DropBox and make it into a service using a free tool such as srvany: jrdata.se/2011/01/20/dropbox-as-a-service –  Sun W Kim yesterday
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6 Answers

there are plenty of rsync solutions for windows. rsync is a software application and network protocol for Unix-like and Windows systems which synchronizes files and directories from one location to another while minimizing data transfer using delta encoding when appropriate. An important feature of rsync not found in most similar programs/protocols is that the mirroring takes place with only one transmission in each direction. rsync can copy or display directory contents and copy files, optionally using compression and recursion.

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rsync can only perform a one-way copy, not real synchronization, making it really hard to handle conflicts (file changed in both sides), additions, deletions... not to mention lack of realtime monitoring. –  grawity Jan 7 '12 at 19:21
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Microsoft has the Distributed File System Technology (DFS) that exists for syncing between servers, but, I have been searching for ages and not found a good solution that works as flawlessly as Dropbox or similar technologies for client computers.

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Vista introduced peer-to-peer DFS. Unfortunately, that won't sync with a server. –  MSalters Jan 10 '12 at 15:32
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The free BestSync utility seems to do what you ask for.

Other possibilities are :

DSynchronize (scroll down to reach)
SYNCING.NET
BlueFish File Mirror
Dropbox : Not only does it sync files in real time, it stores copies and past versions online too.

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Real time sync and network drives aren't supported in the free version. I need it to do this for multiple computers too. –  jnm2 Jan 12 '12 at 2:14
    
I added some more. –  harrymc Jan 12 '12 at 19:08
    
BlueFish says it isn't for two way sync, see my question about DropBox, and Syncing.net is expensive BUT DSynchronize might do what I need. It doesn't look like it does delta sync, but hey, at this point I guess I might have to accept what's available. –  jnm2 Jan 12 '12 at 23:45
    
Only problem, it won't synchronize deletes. It also did not detect a move. –  jnm2 Jan 12 '12 at 23:56
    
I seems to me that maybe the perfect freeware does not exist. In view of your requirements, you might need a commercial product. –  harrymc Jan 13 '12 at 8:30
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If you're looking for a native windows solution, that requires no additional software, you can use "offline files".
From each computer you simply access the folders you need directly on the server, only you turn on the feature "make available offline" for those folders, which will make windows keep a copy of them locally on each computer.
You can even change the location windows keeps these folders at.

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Nice idea. The only thing is I want to edit them locally and that will only happen if I actually am offline from the server, which I don't want to be. –  jnm2 Jan 12 '12 at 23:41
    
Actually that's not a problem: when you edit a file in a folder which is available offline you are editing it locally (even when you are online), and then windows syncs it in the background to the version on server. –  Joe Jan 13 '12 at 7:30
    
When I'm connected I get a big performance hit unless I specifically tell it to go offline, so I think it is going over the network. It's not realtime if I have to switch it on and off manually. Also, I can't do multiple folders for multiple users if I just relocate the cache and edit those files directly. –  jnm2 Jan 14 '12 at 21:19
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I believe Beyond Sync is the tool you are looking for. It isn't free (first 30 days are) but does run as a service and does realtime sync across networks, external devices, etc.

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BestSync does seem to be an amazing product, I may switch to it. However, you must have the Business or Ultimate paid version to do realtime sync. The free version does not allow network sync. Typically I use Allway sync to sync my data from my removable device to my system. Plug in the removable device and it automatically syncs with local folder. –  opsin Jan 10 '12 at 18:04
    
Looks really good except for multiple computer support. I'm going to need something running on each computer for change detection and on the server to manage the synchronization or they'll end up colliding. –  jnm2 Jan 12 '12 at 2:16
    
Not sure I understand. It can run as a service on all the machines. Each machine gets a copy and files are kept in sync instantly on each one. –  opsin Jan 12 '12 at 4:34
    
I'm assuming I'd have each sync client point to the same source to keep the four computers in sync. If two sync clients are updating and reading the same file at the same time, what will happen on the server if there is no software running on the server to manage the collision? –  jnm2 Jan 12 '12 at 13:48
    
For instance, if one computer updates a file and it gets synced to the file server, how will the other computers know to sync with the file server? –  jnm2 Jan 12 '12 at 13:50
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This solution has worked well for me with several systems but does not use your server. I use a Western Digital Live (Duo) and the WD SmartWare aplication . App comes with the drive Once set, it backups up the selected data. Available as a single drive or dual drive RAID 1

SmartWare

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This requires a MyBook. And I need realtime two way sync. –  jnm2 Jan 12 '12 at 23:43
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