Berkeley CSUA MOTD:Entry 25262
Berkeley CSUA MOTD
2019/04/22 [General] UID:1000 Activity:popular

2002/7/2-3 [Computer/SW/Database] UID:25262 Activity:high
7/2     ufsdump manpages say that the filesystem needs to be unmounted to
        do a correct dump. Well, I can't really just unmount the filesystem
        once a week... Do people actually use dump/ufsdump?
        \_ yes.  ignore the manpage.  -tom
           \_ I should say, ignore the manpage unless you're backing up
              something like an Oracle server where the bulk of your
              interesting data is in files which are likely to change while
              the dump is going on.  -tom
              \_ Doing backup of /var/mail on a busy mail server often fails
                 because of files being constantly accessed.
        \_ It's a good suggestion. Would be nice if it were possible.
        \_ Recent Solaris 8 HW releases have a feature called ufs snapshots.
           You can create a read-only snapshot of a file system that doesn't
           change for backup purposes.  I had some problems with snapshots but
           \_ I think the read-only snapshot will have the same problem as
              ufsdump--the files could change while the snapshot is being
              read/written.  -tom
              \_ Not entirely clear on the concept, but is this sort of thing
                 alleviated by jfs?  I.e. does it kind of keep track of
                 what is changing at any given point and back it up
                 correctly?  -John
              \_ but the point of the snapshot is that even if the files are
                 open and being written to, changes wont be made to the files
                 in the snapshot while the snapshot is active... worst case
                 scenario is that something is writing to the file and you
                 only get half the write, but you can come back to the same
                 snapshot an hour later and it will still look like that.
                 \_ Well, sure, you can back up the snapshot without ufsdump
                    failing, but if the snapshot contains files in an
                    inconsistent state (say, an Oracle database that was
                    in the process of writing a transaction), your good
                    ufsdump won't let you restore the system to a consistent
                    state.  -tom
                    \_ that's why it is probably a good idea to stop the
                       database app before taking a snapshot.
                       \_ Has anyone played with Veritas's Oracle backup?
                          I seem to recall it claims to be able to deal
                          with running databases no problem.  -John
                          \_ Yes, it works.  It uses a script to change the
                             Oracle database into backup mode and then does
                             the backup.  And yes, we have been able to
                             restore. You need DBED in order to do any of
                             the fancier stuff.  -mlee
                          \_ Y'know, for all the shit I've talked about it, DB2
                             really made backups very simple.  It's probably
                             not any harder than oracle, but it felt cleaner
                             somehow.  --scotsman
        \_ At one place I was at we did live dumps for dailies and weeklies
           but once a month took everything down and did single user mode
           fulls.  Needless to say this was a total bitch but yes some people
           do this.
2019/04/22 [General] UID:1000 Activity:popular

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