Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!pasteur!ucbvax!RICHTER.MIT.EDU!krowitz From: krowitz@RICHTER.MIT.EDU (David Krowitz) Newsgroups: comp.sys.apollo Subject: Re: more SR10 questions Message-ID: <8812051455.AA06261@richter.mit.edu> Date: 5 Dec 88 14:55:00 GMT Sender: daemon@ucbvax.BERKELEY.EDU Organization: The Internet Lines: 27 The reason that incremental backups with WBAK are so slow is that you wind up having to touch every file on the disk to check the date/time it was last modified. Unfortunately, the Apollo file system does not store the DTM in the directory entry of the file, so WBAK must open each file in addition to opening and reading the parent directory. One way in which backups can be speed up is the method used by Workstations Solutions' backup product. They start clients on several nodes which all feed data back to a server which writes the tape. Since the clients run independently of each other they can process several disks simultaneously and send the server buffers of data which have already been formatted for the backup tape. The only drawback to this approach is that you wind up with files from multiple disks all interleaved in a single backup file on the tape rather than in seperate backups. It is easier to retrieve files from a backup when you know for certain which tape it is on. Incremental backups, however, are frequently done which several disks all on a single tape, in which case the method used by Workstation Solutions gives the same results a whole lot faster. -- David Krowitz krowitz@richter.mit.edu (18.83.0.109) krowitz%richter@eddie.mit.edu krowitz%richter@athena.mit.edu krowitz%richter.mit.edu@mitvma.bitnet (in order of decreasing preference)