Hardware aside, you need a journaled filing system, as Jakob suggested. Journaling works via transactions, and is used in more than just filesystems. Microsoft SQL and Exchange are two products I know that use journaling. Here's how it works. Let's say we want to remove $100 from your bank account and put it in mine. First we subtract $100 from yours, then add $100 to mine. If the computers crash after removing money from yours that $100 is lost in a non-journaled banking system. If it was journaled, it would go like this: Begin Subtract $100 from bob Add $100 to cory commit Either both things happen, or neither. The transactions are put in to a log file. Once the begin and commit are in the log, the database(or filesystem) is then updated. This enables a filesystem or database to erase unfinished transactions, without caring what they did to the filesystem (because they didn't do anything, yet). With ReiserFS, you can pull the plug on it. When it boots up the filesystem doesn't check the whole system like ext2fs. Instead it only looks at it's transaction log, and either erases or commits transactions. There is the possibility of the outage happening at just the wrong moment.... However, this is clearly a better approach than a non-journaled filesystem for a redundant application. The ReiserFS sits on top of the ext2fs. Mike was telling me about the X file system that is coming out. Also journaled. (Has nothing to do with XFree86). Perhaps he can share a bit. Cory -----Original Message----- From: Bob Crandell [mailto:[EMAIL PROTECTED]] Sent: Thursday, December 07, 2000 3:29 PM To: [EMAIL PROTECTED] Subject: [EUG-LUG:5216] Mirror Question: Is there a mirroring solution for Linux that is reliable? For example, in the middle of copying a file to the drive, pull the plug. Do you loose the file? or the whole partition? Explanation: I built a NAS box for a client. It interacts with Novell 5.1 and is an FTP server for an Axis scanner. This box also serves a CDROM tower. That's why I didn't sell them a SNAP. The Problem: The mother board choked on a bone or something and went down. When I finally got it back up, the mirrored drives were toast. I'm glad I told them to wait.
