tim.conway@philips.com
2002-Nov-15 23:17 UTC
RFE: using rsync as a backup tool (preserve access time & com press destination files) ?
The way gnutar "preserves" atime is by noting it before the read, and setting it back after the read, thus wiping out a legitimate setting of atime occuring during that interval. Yeah, the netapps mess with unix times. Did you notice that mtime and ctime always match? Now that I know you're on a netapp, though, your problems are solved. Snapshot and sync from the snapshot, then expire the snapshot if your data is rapidly-changing, so it doesn't hold a bunch of old space. Also, I just mounted up a netapp readonly (on a system also mounting same directory readwrite elsewhere). even though it's readonly, the netapp sees the read and updates atime... however, I still like the snapshot idea. Tim Conway conway.tim@spilihp.com reorder name and reverse domain 303.682.4917 office, 303.921.0301 cell Philips Semiconductor - Longmont TC 1880 Industrial Circle, Suite D Longmont, CO 80501 Available via SameTime Connect within Philips, caesupport2 on AIM "There are some who call me.... Tim?" Gilles-Eric Descamps <Gilles-Eric.Descamps@SiliconAccess.com> 11/15/02 03:50 PM To: Tim Conway/LMT/SC/PHILIPS@AMEC cc: Subject: RE: RFE: using rsync as a backup tool (preserve access time & com press destination files) ? Classification:> From: tim.conway@philips.com [mailto:tim.conway@philips.com] > Sent: Wednesday, October 30, 2002 10:53 AM > > It's not up to the application whether atime gets updated. > That's like > complaining about find making your hard drive light flash. > The only thing rsync could do would be to note the atime > before reading > the file, then falsely set it back to what it was, after > reading the file, > and hope that it wasn't set to something else in the > interim... a kludge > at best.Well, gnu tar provides a "--atime-preserve". All applications which backup filesystems (legato, quickrestore, budtools) preserve times on an application level. A backup tool is supposed to bypass normal filesystem access as it's supposed to be transparent.> Why not mount the filesystem on an alternate mountpoint, noatime or > readonly? On AIX, you can just mount the dir wherever. In sun, and > apparently Linux, nfs export it, only to localhost, if you > like, and mount > it readonly. As Chef Tell used to say, "very simple, very easy", and > legitimate setting of atime can continue unhindered.Because that does not work. I just tried it. The file server is a NetApp box running a proprietary OS (not unix, nor windows). mounted the NFS filesystem with noatime & readonly, but guess what, when you read a file, the box updates the read time