> > One more time: Unless your Linux systems *are completely down* at the > > time of backup, full volume dumps from outside the Linux system are more > > than likely to be useless. > Can you explain why is that ?
Linux performs in-memory caching to a much greater degree than most operating systems to do I/O avoidance. Data in buffers that has not yet been written may not be actually committed to the filesystem yet, and repeated use of /bin/sync or a system quiesce is no longer is a guarantee that the OS has flushed all pending buffers. Journaling can only replay transactions that have been committed to the filesystem, so there is an opportunity to lose data between the termination of a write and commit to the journal. On a busy filesystem, this can be a fairly serious exposure. Second reason is that most distributions still use ext2 for the root filesystem to avoid problems with boot-time errors and not having the necessary filesystem modules in the initrd to do recovery. Reiserfs has some particularly evil problems -- when it works, it's great. When it breaks, it's a complete iron-plated b*tch to repair. Ext3 is better in that it can always be mounted as ext2, but still is a higher risk than having good internal backups. Since you're booting from this system, screwups here are less than forgiving, as the system is pretty brain-dead at this point. > I never experimented such failure after doing live backup of journaled > filesystems. You have gotten extremely lucky. > It is like brute forcing a shutdown by logging off the VM machine : not > ideal, but not supposed to break your Linux machine. You probably know this, but a good reminder: you should absolutely do a *controlled* shutdown before taking backups -- no point in backing up a filesystem you *know* is horked due to a unclean shutdown. As Alan said, it's a question of one system knowing what's happening on the other system. There's no way that z/OS is going to be able to know that the Linux system is "safe" (without some kind of automation on BOTH systems to be able to signal same) so dumps taken from outside the Linux system (even with hardware features like flashcopy) are going to be inconsistent. ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
