Charles - When you did this: "so we used the same double mirror/pause/split/tape backup as described by others"
How many disks were in your array and were they all raid 0? What kind of controller were you using that was doing a Raid 0+1+1?? Sounds like you were on Universe, was it windows as well? Kevin Gusler Applications Developer Mortgage Builder Software, Inc. Main: 800.850.8060 ext. 106 Fax: 248.304.0601 www.mortgagebuilder.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Charles Stevenson Sent: Tuesday, June 23, 2009 3:30 PM To: U2 Users List Subject: Re: [U2] FW: Valid Backup on Windows Universe >> Why do you think this? >> >> "The failure I see of this system is that even though the db is >> paused, it >> is not in a "safe" state for backup." >> Once you broke the mirror would it not be safe to backup that array?? > The db is basically in "mid sentence". The commits are not atomic. > If you restore to the tape, you may in my case have "half an order" or > an invoice half processed. the unidata dbpause does not make people > get out of maitnenance screens or release locks, so records can be in > an uncommitted state. Risk is small, but it is present. Yes, have integrity at the UD & OS level , but application layer may lack integrity at the logical transaction level. I don't know UD, but on UV this can be mitigated by using Transaction Logging in simple checkpoint mode, if nothing else. Your programs do not need to have transaction start/commit structures to take advantage of this. This is really "update", not "transaction", logging. I administered a system that didn't use Transaction Logging because of a bug (I think it's been fixed). We decided that our ap could live with a couple half baked transactions in the event of a restore, so we used the same double mirror/pause/split/tape backup as described by others, with one variation: We left the mirror split and stale for most of the day. That way if problems arose (e.g., broken file, file cleared inappropriately, etc.) I had fast access to the previous day's data. I occasionally took advantage of that feature. We never had a catastrophic failure during my tenure, but restoring from the stale mirror would have been much faster than restoring from backup tapes. _______________________________________________ U2-Users mailing list [email protected] http://listserver.u2ug.org/mailman/listinfo/u2-users _______________________________________________ U2-Users mailing list [email protected] http://listserver.u2ug.org/mailman/listinfo/u2-users
