Les Mikesell wrote: > On Mon, 2006-11-06 at 14:54 -0800, Mark Schoonover wrote: > >>> Note that this only works as a backup if the original filename is >>> removed. If it is overwritten or truncated instead, all links now >>> point to the changed version. >> >> This is true if you're doing it with only filesystem tools, but this >> system is using rsync. What's happening is the cp -al occurs first >> making hardlinks that point to an hourly directory into the current >> directory, then rsync is run to update current. Because rsync will >> create a new temp file when any file changes, the original is >> deleted with it's data 'pushed' to any hardlinks pointing at the >> original file. Rsync then renames the temp file the original file >> name that has changed, therefore assuring that any hardlinks will >> always have the previous copy of any changed files. With rsync >> running in --delete mode, any files from the source server that get >> deleted, will get deleted out of current in the backup server, >> causing this cascade of hardlinks to get updated with the deleted >> files data. That's how this system can create incremental backups of >> only changed data, but with hardlinks, it looks like full backups >> are made each and every time. Really saves disk space, that's for >> sure! >> >> Hope this clears things up... > > Backuppc is even more extreme in the space savings. It first > compresses the files, then detects duplicates using an efficient > hashing scheme and links all duplicates to one pooled copy whether > they came from > the same source or not. It includes a custom rsync on the server > side that understands the compressed storage format but works with > stock versions on the remote side so you don't need any special client > software. And it has a nice web interface for browsing the backup > archive and doing restores. Sounds like a good product! Since I had plenty of terabytes of storage, having compression on the files wasn't a requirement. One of my requirements was not having a gui to configure things, or do restores. Thanks for pointing some info out on backuppc, I've never heard of it. Mark