On Monday 28 October 2002 1:41 am, Jens Vagelpohl wrote:
FileStorage only appends at the end of the file.
Not entirely true. FileStorage still supports a non-transactional undo mechanism that writes bytes to the middle of files. This mechanism is not normally used by Zope, however it might be used by other non-Zope ZODB applications, or custom products. (could it be exploited by an attacker who wanted to break your backups? hmmmm) Proviing that this type of live backup is safe requires knowledge about how the backup program will read the file. The obvious approach of reading from start to end is compatible with FileStorages append-only approach, but not all backup programs operate that way. I prefer to take a copy of the data.fs using 'cp' (which I know to be safe), and backup that.
why don't you just try and see how it works?
Thats a fantasically dumb approach for testing a backup strategy. Just because you cant see any problems on a couple of test runs, it doesnt mean: 1. there arent any hidden problems. 2. there wont be obvious problems when you come to rely on your backup.