[Zope] backup full instances
jonas at freesources.org
Sat Oct 27 12:18:23 EDT 2007
On 27/10/2007 Andreas Jung wrote:
>>> If you create a local copy, it is safe. If you rsync a running Data.fs,
>>> it is not safe. In this case you create a local copy and rsync the copy.
>> but if rsync is unsafe only because it takes long time, and changes on the
>> instance during the copy process could cause a corrupted Data.fs to be
>> backuped, then theoretically this could happen for a local copy as
>> well, right?
> Think twice about your last sentence. What should cause a local *copy*
> to be changed??
zope might write to the Data.fs while it is copied, thus an inconsistent
copy would be backuped, even inside one filesystem.
i've asked in #debian on freenode as i wasn't sure, here's the log:
< mejo> if i copy a large file inside a mounted filesystem (ext3), is it
possible that the file is changed during the copy process?
< Wyzard> mejo: Yes, it's possible that something else can write to the
file while you're copying it
< mejo> because i asked on the zope-users mailinglist if i could backup
the global Data.fs (database) while the daemon is running, and
< mejo> If you create a local copy, it is safe. If you rsync a running
Data.fs it is not safe. In this case you create a local copy
and rsync the copy.
< Wyzard> mejo: Making a local copy is faster, so it'd be safer, but
still not completely safe
< mejo> exactly, that's what i thought as well.
< mejo> but when i wrote that, he replied:
< mejo> Think twice about your last sentence. What should cause a local
*copy* to be changed??
< mejo> so he's wrong?
< Wyzard> I'd say he's wrong
< Wyzard> A local copy isn't instantaneous, and Zope changes the file
while it's being read
< wols_> he is wrong yes
< mejo> thanks. is it ok for you if i quote you in my reply mail?
< Wyzard> mejo: sure
< wols_> mejo: while copying zope could change the database and create
an inconsistent state
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