[Zope] Copying Data.fs (was Re: Using XRon to backup my portal)

[Toby Dickenson]

On Monday 28 October 2002 1:41 am, Jens Vagelpohl wrote:
> FileStorage only appends at the end of the file.=20

Not entirely true. FileStorage still supports a non-transactional undo=20
mechanism that writes bytes to the middle of files. This mechanism is not=
=20
normally used by Zope, however it might be used by other non-Zope ZODB=20
applications, or custom products.=20

(could it be exploited by an attacker who wanted to break your backups? h=
mmmm)

Proviing that this type of live backup is safe requires knowledge about h=
ow=20
the backup program will read the file. The obvious approach of reading fr=
om=20
start to end is compatible with FileStorages append-only approach, but no=
t=20
all backup programs operate that way. I prefer to take a copy of the data=
=2Efs=20
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 be=
cause=20
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.