rsync to servers highly sensitive to IO load
jeff.woods at choicepoint.com
Mon Jul 14 11:47:55 GMT 2008
Perfect! It sounds like "--append" it the magic bullet in this case...
Wayne Davison wrote:
> On Fri, Jul 11, 2008 at 10:10:16AM -0400, Jeff Woods wrote:
>> --bwlimit=17 --partial --append
> You only want to use --append if you can guarantee that the files will
> not have any changes in the existing data on the receiving side. A
> modern rsync does not compute a full-file checksum for --append unless
> you use a second --append, since that slows down the appending.
> If you're using -c (--checksum), you probably don't want to do that,
> since that's super slow. Just use -t (--times) and let the normal
> size+mtime check look over things for you. If you find that you really
> need checksumming, you might want to look at the db.diff in the patches
> dir that lets you cache checksums in a DB (i.e. SQLite or MySQL) and
> associate them with unchanged files (since it matches a file's size,
> mtime, ctime, and inode, it is safe).
> If the source of the I/O is rsync's scanning of the directories (not the
> checksumming of the files), you may want to look into the slow-down.diff
> file in the patches dir, as that provides a way to get rsync to do its
> directory scanning more slowly.
>> negating the need to re-read the entire file for a post-transfer
> There is no such thing in rsync, since it computes the checksum as the
> file is written.
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