On 10/29/2010 12:53 PM, Richard Shaw wrote: > >>> For instance: I can understand how tar over SSH transfers files. But >>> who decides what files to transfer? >> >> Your file include or exclude lists are mapped into the options >> appropriate for the xfer program with the 'share' as the top of the tree. > > So in effect, BackupPC doesn't do anything directly, but rather > indirectly by proxy? (not the network meaning, but the literal > meaning).
Yes, the program selected by the XferMethod is used to access the client. >> With tar and smb, backuppc doesn't know much about the remote side - it >> just passes the options to the program. Tar runs over ssh entirely on >> the remote side. > > So with tar/smbtar for a full backup all files are transferred? In > other words there's no checksum on the remote client to see if it > already exists? Yes. Then existing files are discarded on the server and replaced with links to the pooled copies. >> The rsync method runs a native rsync via ssh on the remote side, using a >> perl implementation on the server. Rsyncd is similar, but talks to a >> standalone rsync running in daemon mode that must be set up on the >> target. Rsync sends the entire directory tree you request from the >> remote, then both sides walk the list to find and send differences. > > I assume that the checksuming that rsync does can create quite a CPU > load on the client which is why on linux clients are often nice'd? (or > ionice?) It is more of an io load than CPU since disks are much slower than processors. And rsync incrementals quickly skip files where the directory name/length/timestamp match the previous full. Full runs add the --ignore-times option to rsync so all files are read for the checksum comparison but only the differences are sent over the network. -- Les Mikesell lesmikes...@gmail.com ------------------------------------------------------------------------------ Nokia and AT&T present the 2010 Calling All Innovators-North America contest Create new apps & games for the Nokia N8 for consumers in U.S. and Canada $10 million total in prizes - $4M cash, 500 devices, nearly $6M in marketing Develop with Nokia Qt SDK, Web Runtime, or Java and Publish to Ovi Store http://p.sf.net/sfu/nokia-dev2dev _______________________________________________ BackupPC-users mailing list BackupPC-users@lists.sourceforge.net List: https://lists.sourceforge.net/lists/listinfo/backuppc-users Wiki: http://backuppc.wiki.sourceforge.net Project: http://backuppc.sourceforge.net/