Date: Wed, 31 May 2000 10:15:43 +0800 (TSD) From: Victor Sudakov <sudakov@sibptus.tomsk.ru> To: keith@mail.telestream.com Cc: questions@freebsd.org Subject: Re: Anyone using dump(8) Message-ID: <200005310215.e4V2FiF13627@sibptus.tomsk.ru> In-Reply-To: <Pine.LNX.4.10.10005292244240.27088-100000@mail.telestream.com> from "keith@mail.telestream.com" at "May 29, 2000 11: 6:51 pm"
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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? ;-) > 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. > 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. > > > 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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