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Hi Wayne, Thanks for your response - it's much appreciated. Comments below Wayne Davison wrote: The only checksum that is being cached is the one that the user can optionally request for a pre-transfer check. It's not usually needed, unless the "quick check" algorithm (size + mtime) has a chance of being wrong. In our case, the mtime is going to be different, since users would be installing a game from a CD and they would have an mtime from that initial install, so checksums would be needed. A better update strategy would be some kind of a binary patch algorithm.You may want to check into some other binary-patching software to see what your options are (I haven't looked into it). We've looked briefly at rsync's batch mode, but using that would likely be pretty similar to several other binary-patching solutions out there, and we'd have to go through the complexity of dealing with updates from multiple different source versions, which would add development work I was hoping we might avoid by just using rsync directly.
I'm a bit confused still on this last point - would the cached checksums from the checksum-updating patch mean that the server would only have to be doing the block comparisons? Or would the server still need to calculate the checksums themselves for every client? IE: are the individual block checksums within a file cached by the checksum-updating patch, or is it just caching an overall file checksum? Also, is it the server that does the block comparisons and decides what data to send, or does that happen on the client? If it's the server, that would certainly be a bunch more overhead than I was thinking. >From the "How rsync works" document (http://samba.anu.edu.au/rsync/how-rsync-works.html), it sounded like the receiver (aka client) became the 'generator'. I guess I was thinking that the generator was responsible for requesting the individual blocks. A re-read suggests that it is in fact the server that has to do the block comparisons as you seem to be suggesting. Wouldn't it be more efficient in general for that to happen on the client side though? One side certainly has to transfer the block checksums over to the other side, so why not make that be the server rather than the client and have the client do the block comparisons and then request individual blocks from the server? Take care, -Gav -- Gavriel State, Founder & CTO TransGaming Inc. [EMAIL PROTECTED] http://www.transgaming.com Broadening The Playing Field |
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