senetza@honte.uleth.ca (Len Senetza) (05/22/91)
I'm wondering how dump handles open files. Does it back them up? Does it skip them? Does it trash them in the process of backing them up? I realize that having a file open while dumping (or any other type of access) can have unpredictable results, but I wanna know how dump handles it. See, when we do our backups we don't shut-down to single user mode. We have a DECserver 3100 serving 2 DECstation 3100's and 22 VAXstation 3100's in a computing science lab. This stuff has to be running almost continually (hardware failure is practically the only excuse). So, we have to do live backups. I'm not trying to start a flame war about how to do backups and all that -- I know, and we have to take the risk of losing a couple of files here and there. I just want to know how dump handles open files. Oh, we're currently running Ultrix 3.1D. Yes, we are upgrading to 4.2 ASAP. -- Len Senetza Internet: senetza@hg.uleth.ca <preferred> Academic Consultant senetza@honte.uleth.ca University of Lethbridge Lethbridge, Alberta, Canada
grr@cbmvax.commodore.com (George Robbins) (05/25/91)
In article <1991May22.145513.15048@honte.uleth.ca> senetza@honte.uleth.ca (Len Senetza) writes: > I'm wondering how dump handles open files. Does it back them up? Does > it skip them? Does it trash them in the process of backing them up? I > realize that having a file open while dumping (or any other type of > access) can have unpredictable results, but I wanna know how dump > handles it. Basically, dump "reads" the files and puts what it reads on the tape. If the size of what it reads doesn't agree with what the i-node said initially, then you get a warning message that the file size changed. If the file is simply "growing" than this is probably reasonably competent behavior. If some other nature of updating is going on, then you'll have to assume that the image of that file on the backup tape is not neccessarily consistent, but but perhaps better than no dump. The real risks come from files that are added / deleted or suffer radical size changes during the dump. Traditionally, it was easy to generate a dump date that would blow off the restore because the data on the tape was confused. Supposedly, the current Ultrix dump has been ruggedized and this problem is minimized. > See, when we do our backups we don't shut-down to single user mode. We > have a DECserver 3100 serving 2 DECstation 3100's and 22 VAXstation > 3100's in a computing science lab. This stuff has to be running almost > continually (hardware failure is practically the only excuse). So, we > have to do live backups. There is no big problem with doing incremental dumps on live filesystems, but you are taking a major risk if your level 0 dumps aren't done single user or with the filesystems unmounted. If you do frequent full dumps to then you can probably live with the possibility of one of them being unrestorable. -- George Robbins - now working for, uucp: {uunet|pyramid|rutgers}!cbmvax!grr but no way officially representing: domain: grr@cbmvax.commodore.com Commodore, Engineering Department phone: 215-431-9349 (only by moonlite)