oberman@LLL-ICDC.ARPA.UUCP (06/12/87)
>Why do people still shut down systems, regularly, for long periods, to perform > standalone backup? >Although I've had to perform full and selective disk restores on several > occasions, the backups made have been with /IMAGE/IGNORE=INTERLOCK on a > running system. I haven't observed any disk file problems when this has been > done. >What are the REAL issues ( as opposed to imagined )? Remembering that system > crashes and other hardware/software failures can prevent writing of data > currently in memory on to disk, what extra security does the standalone > back-up provide? First off, I don't do standalone BACKUP very often. My regular BACKUPs are done on-line. But... I realize I am taking a risk in doing it this way. Just a small one, though. BACKUP does a snapshot of the current contents of a file while BACKUP is in progress. If that file is in some intermediate condition -- OOOPS! The odds of this happening are small but real. I suppose a worst case would be the extension of the Index File. This may not be possible, but I suspect that with really rotton luck you could have a real mess. In 7 years of doing BACKUP on-line and several disk failures, the worst error was when BACKUP was screwed up and didn't do incremental restored correctly. (V3.3?) This had nothing to do with doing the BACKUP on-line. The only significant failure caused by on-line BACKUP was the corruption for my job queue data file. It cost less than 30 minutes to get everything set up right again. It would take less time now as I have command files to do most of the work. Compared to up to 6 hours a month with each disks unavailable, I'm willing to take the risk. You may not be. In environments where there are critical or non-reproducable data files of high value I might do things differently. If anyone sees some important issue I am missing, please let me know. R. Kevin Oberman Lawrence Livermore National Laboratory arpa: oberman@lll-icdc.arpa (415) 422-6955 Disclaimer: Neither my employer nor myself can take resposibility for the accuracy of this information. I believe it is correct, but if it's not I can only say "Sorry". I'm a rotten typist and a worse speller, so forgive any silly errors. ------