Hello Xu, I don't mean to be parental, but this should be a good reminder to you that > it's always good to save frequently and to save many different versions. > Ideally you should look into a version control system (which LyX actually > supports!), but at the least, make multiple backups, and not just one one > machine.
Or, to remember that a back up exists!! All my documents are in a Dropbox folder which is then synced to three different computers including one off site, as well as the Dropbox servers. Dropbox records a snapshot of every save for the last 30 days, and saves them on their server. They also do a paid version which saves snapshots for longer than 30 days. I save frequently, indeed looking at the log on Dropbox I seem to save every two to three minutes and I have 22 pages of snapshots. I had forgotten all about this until your comments above. However, the free Dropbox solution isn't going to help if I come back to a document in 6 months time, as it only keeps the versions for 30 days, rather than keeping 30 days worth of versions (if you see what I mean), which I hadn't realised. So I will need to think about that, and thanks fro raising it. Graham
