Need A Linux Music Manager
Reply #26 – 2011-02-20 11:43:57
the bonus with rsync is your guarunteed a bit for bit exact duplicate, no silent corruption during copy, and any corupted files on the backups will automatically get updated from the source . This is only true if you select the rsync -c option, which creates a temporary CRC for each file on the client and server, and compares the CRCs to decide if it needs to update or not. If you don't use the -c option then rsync compares file size and last edit time, and uses that to decide what needs to be copied across - and (as I am discovering) that means you can have corrupted files on either the source or the backup and not realise it. Worth noting that the tradeoff of -c option is the evaluation time, which results from CRC calculation on both sides and comparison. In case of big archives with a large number of relatively small files, it may become really long, even on fast CPUs and fast disk access, some magnitude order bigger than the time actually needed to transfer data. This is still an advantage where completion time is not an issue but bandwidth usage is, say overnight backup over slow wan connections. If you're not making a real backup to store, forget and (hopefully!) use in case of disaster, but only mirroring to multiple places a set of sufficiently static data (all in all you won't update all tags everyday!), then do not use -c. Even if in a place a file is corrupted and you notice it, chances are you can always restore it from a good copy somewhere else.