[ZODB-Dev] Is there an official patch for the problems with packing and data loss?

[Toby Dickenson]

On Tuesday 13 May 2003 7:34 pm, Joachim Werner wrote:

> People really get scared about ZODB ... - I for myself don't
> trust it any more :-(

You _may_ want to have a look at DirectoryStorage. One of its design goals was 
to mitigate these fears. If DirectoryStorage should have a bug like this 
recent one in FileStorage then it wouldnt be so serious, because this type of 
packing damage can be recovered (without needing a backup) provided it is 
discovered within some user-defined safety period; 10 days by default.

Implementation simplicity is also a goal for DirectoryStorage. It uses the 
same back pointers involved in the recent FileStorage fix.... FileStorage 
uses its back pointers for two purposes; tracking undoability and to save 
space by sharing pickles between undone transactions. DirectoryStorage doesnt 
try to share pickles. It burns though disk space if you use alot of undos, 
but reduces the chance of data loss through this type of bug.

I dont want to oversell DirectoryStorage. Before this round of FileStorage 
changes, DirectoryStorage probably had more bugs than FileStorage. I do hope 
the bugs in DirectoryStorage have a less serious impact.

-- 
Toby Dickenson
http://www.geminidataloggers.com/people/tdickenson