Date: Tue, 30 May 2000 22:38:11 -0700 (PDT) From: <keith@mail.telestream.com> To: Victor Sudakov <sudakov@sibptus.tomsk.ru> Cc: questions@freebsd.org Subject: Re: Anyone using dump(8) Message-ID: <Pine.LNX.4.10.10005302233410.19232-100000@mail.telestream.com> In-Reply-To: <200005310215.e4V2FiF13627@sibptus.tomsk.ru>
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On Wed, 31 May 2000, Victor Sudakov wrote: > keith@mail.telestream.com wrote: > > I use dump every day. Seeing that I had a million of my questions > > answered from the list not to long ago I'll repay the debt on your > > questions. :) > > > > #1 If file systems are to be mouted read only durring a dump then it's > > news to me. I've never heard of it and have never done it. A quick look at > > the man page for dump doesn't say this either. > > I remember reading somewhere that the file system should be quiet. > Just imagine that a file is modified in the middle of the dump, after > the mapping. Besides, a file can be in the disk cache etc. > > > > #2 I use dump for 5 servers on my network to a single machine. > > Did you read the tapes after the dump? ;-) Of course, :) I've had the pleasure many times of restoring files that I've judiciously screwed up or just flat out hosed. :) > > > Works realy good. You have to allow for rsh because dump will use it to do > > the dirty work. Not exactly secure but if you aren't doing dumps in a cron > > script then you can just enable rsh durring the times you prefer to do the > > dumps. > > > > #3 You don't have to be single user to do a dump. That would kind of > > defeat the use of a network dump. > > > > #4 I'm not entirely sure about this but as far as doing a dump on an > > active file system. Dump takes a sort of snapshot of the file system > > before it starts pumping data to tape. So files modified durring a dump > > will only have the data as it was before dump took the snap of it. > > As soon as you issue the dump command your disks will go crazy as dump > > figures out what all needs to be dumped. I just kind of assumed <ouch> > > that it was snaping the file system. Or depending on the level of dump you > > When dump(8) dumps a 10 Gigabyte filesystem, there is certainly no > room for another 10 Gigabytes for a snapshot. > Good point, like I said in that mail though. "Assumed" it was "some kind" of a snapshot.. Not a snapshot. > > are doing will be looking to see the modification dates on files to > > determine what needs dumping. > > Anyone with more info on this I'd like to know about it. > > > > > > #5 I've never known anyone to halt services while dumping a file system. > > So what is going to happen to the files that change during the dump? I > think they will be unreadable because dump mapped them with their old > size and will have dumped them with a different size or truncate the > end of them or whatever. This is one of those things I'd realy like more clarification on from somebody "in the know" on this. > > > > > > > Hope that answered some questions. > > > > Keith W. > > > > At the helm <for better or worse> > > ================================= > > > > > > On Tue, 30 May 2000, Victor Sudakov wrote: > > > > > Hello. > > > > > > I wonder if anyone uses dump(8) nowadays in a production environment. > > > It seems the best backup tool as it preserves hard links, sparce files > > > etc. However, there are some practical questions I need enlightment > > > on. > > > > > > 1. You are supposed to mount a filesystem readonly before you dump it, > > > right? Then dump cannot write /etc/dumpdates and aborts. Moreover, I > > > cannot stop the services every time I need to dump a filesystem. How > > > do you deal with that? > > > > > > 2. The tape drive is only on one host, so I need to dump filesystems > > > over the network. I can boot in single user mode, mount the > > > filesystems readonly, but then I have to do all the ifconfig, route > > > etc. stuff (to see the tape server) by hand which is annoying. > > > > > > 3. Is dump really so vulnerable to modifications of filesystems during > > > dump? Then how is it supposed to work on non-stop systems? > > > > > > Surely there must be some know-how. People seem to have been using > > > dump(8) for years, and in huge companies too. I only have to dump 11 > > > boxes, some with very important data updated every 20 minutes or so, > > > to a tape drive on one of the boxes. Dump users, please reply. > > > > > > Any input is greatly appreciated. > > > > > > -- > > > Victor Sudakov, VAS4-RIPE, VAS47-RIPN > > > 2:5005/149@fidonet http://vas.tomsk.ru/ > > > > > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > > > with "unsubscribe freebsd-questions" in the body of the message > > > > > > > > -- > Victor Sudakov, VAS4-RIPE, VAS47-RIPN > 2:5005/149@fidonet http://vas.tomsk.ru/ > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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