Sunday, February 18, 2007

Re: Xdelta 3.0p (download)

Xdelta-3.x processes a window of input at a time, using a fixed memory budget. This release raises some of the default maximums, for better large-file compression. The default memory settings for large files add up to about 100Mb. (*)

A user wrote to confirm good performance on 3.7Gb WIM files, great!At the other extreme, a developer wrote to ask about using xdelta3 in the Xen kernel. Here's an example of xdelta3 configured for a 4Kb page using 32Kb.

A user writes about code size:Thanks! Xdelta3 is faster and better than Xdelta1 with compression disabled (the -0 flag), thanks to VCDIFF and other improvements.

I'm looking for your ideas on recursive directory diff. One solution uses tar:This approach is better than computing pairwise differences, since data can be copied across files/directories. Pay attention to file order and source buffer size. Microsoft developers, consider using the WIM disk image format.

Thanks for the feedback (file a new issue).

(*) Xdelta-1.x processes the whole input at once, and its data structure takes linear space, (source file size/2)+O(1). Xdelta-1.x reads the the entire source file fully two times (to generate checksums, to match the input), using at least half as much memory as the source file size.

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