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Re: Speeding up slooooowwww extractions
On Thu, May 27, 2021 at 01:11:03AM +0200, hvjunk wrote:
> Another “Request” - File Checksums (SHA256/etc.) in the ‘-tv’ (or -tvv)
> output - that way I can check whether the backed up / stored file in the
> archive is similar to the one on disk - especially usefull when doing
> things like the above, and then with a -tvvv each block’s checksum
File checksums would be tricky, since Tarsnap stores chunks rather than files.
But I have some experimental code from a few years ago which adds something
similar to this for creating an archive (potentially with --dryrun).
(c mode only) If a file has not changed, read it anyway (with the given
probability p from 0.0 to 1.0) and compare its hash(es) and trailer to the
cached values. This might provide a warning about a failing disk if other
detection methods fail. However, this operation will make Tarsnap run
considerably slower, so we do not recommend using a high probability with
There were a few details in that code which needed to be cleaned up.