Jon Lewis wrote:
Can you cite an example of a file that can't be copied on a "running system?"
All files that are open for writing at the time of the copy risk being copied incompletely. Use lsof to find them (but that's a snapshot).
Sure, there are issues if the system is really up and running multi-user with log files that will be copied partially and probably end up terminated with extra nulls, database files may have issues (i.e. mysql if you don't flush and lock the tables, copied tables will be corrupt but are usually trivially repairable), but I've never heard of files not being at all readable.
I submit that these issues, even if you regard them as trivially repairable, are best avoided altogether by making the copy while the filesystem is not in use. And "trivially repairable" presupposes that you know that there is something to be repaired in the first place, and then that you know how to do it. Some of these issues may not manifest themselves until some time after you've begun using the flawed clone, at which time you may have forgotten all about this, may no longer have access to the original data etc.
To the OP: if you want to limit downtime resulting from the fact that the clone has to be made while the filesystem is not in use, you can use rsync to make your copy while the filesystem is still in use (but this copy will be incomplete/flawed etc), and then use rsync again after you've booted from a CD or whatever. The second rsync run will be much faster because it will only copy the files that have changed since the first run, including those that were open at the time of the first run.
Cheers, Jan -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
