DirectoryStorage is a robust, manageable, fault-tolerant, scalable storage for ZODB. http://dirstorage.sourceforge.net/ A bug has been discovered affecting all currently released versions, which can cause data loss when packing. A necessary condition for triggering this bug is for some storage files to be owned by a uid different to that of the storage process at the point the pack is run. This scenario will not occur naturally during normal operation - no storage will be affected by this bug unless an administrator has been manually changing ownership of files or processes. All damage caused by this bug can be manually undone using DirectoryStorage's delayed deletion feature, provided the damage is discovered in time. In the default configuration, within 10 days of the pack that caused the damage. For more information see http://dirstorage.sourceforge.net/FAQ.html#deleted The damage will appear as a POSKeyError when accessing damaged objects. All damage caused by this bug can be detected using DirectoryStorage's checkds storage checking tool. If checkds finds no problem then your storage is clean. Please raise any questions about this problem on dirstorage-users@lists.sourceforge.net. Fixes will be made available shortly. My apologies to anyone inconvenienced by this issue. Thanks to Matt Hamilton for uncovering the problem. Toby Dickenson