Synchronizing Data between WinFS Stores

re: Synchronizing Data between WinFS Stores

Rajendra — Sat, 28 Jan 2006 22:09:42 GMT

Can the sync'ing be in real time? I would like two folders to mirror the same data, so if one drive crashes I'll still have my data in the other. This would be useful for My Documents folder. Sort of poor man's RAID for folders. Not sure how shadow bacups wold fit in or hppen .. i suppose each folder is treated separate? I heard there is an existing non WinFS solution from microsoft already for this. Of course if drave crashes i wouldn't want the crash part to get sync'd lol.

re: Synchronizing Data between WinFS Stores

Aaron Oneal — Sat, 04 Feb 2006 16:58:53 GMT

Greetings,

Overall, I'm very impressed with the sync capabilities of WinFS and the well thought design. As such, I am interested in working with the synchronization features WinFS affords in a peer-to-peer environement, particularly WinFS-to-WinFS, but I have some concerns regarding scalability and versionability.

In the SDK documentation, I noticed the section below that indicates changes to backing streams are not versioned in a way that would allow for access to previous revisions or to discern individual change regions. Am I correct that synchronizing any file backed item is going to require that the entire stream be sent to the remote store even though only a small portion of it may have changed? Is there any way to get at the write logs so that only changed regions of the stream need to be synced?

For example, say I were to use WinFS to store a file backed AVI, WMV, or MP3 file and I alter one of the meta-data properties of the native file format such as Genre, Author, etc. which today results in the alteration of a few bytes of the file stream. I presume that currently OpenBackingStream will throw InconsistentStreamAndDataException until I get to the revision that matches the latest backing file revision and at that point I have to send the entire stream over the wire?

It seems to me that WinFS is likely logging the write regions during operations to a backing file, and if so, it would be great to be able to get at those through the API. Is this type of incremental file synchronization already in place or being planned?

Thank you,
Aaron

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Unlike other "WinFS" data, file streams that are changed in "WinFS" do not maintain snapshot history during change enumeration. Therefore, it is possible that the backing stream of a file-backed item is out of sync with the version metadata during change enumeration. However, when System.Storage.Sync.ItemChange.OpenBackingStream is used, this condition can be detected.

re: Synchronizing Data between WinFS Stores

Aaron Oneal — Sat, 04 Feb 2006 18:34:33 GMT

With respect to my earlier post, I see that WinFS supports File Transfer Compression which addresses to some degree the concern I had over large file transfers due to small changes. I assume what's going on under the covers is a kind of block hashing to identify the changed portions of the file as opposed to write log utilization. Does this hashing occur with every replica synchronization or is the information saved behind the scenes for later use when syncing to multiple replicas in a peer-to-peer environment? Are there any plans to support mesh-to-peer synchronization so that portions of large files can be acquired from various peers within the mesh as opposed to always syncing with one remote endpoint which may or may not be the most performant given locale or other factors?