[Zope-Annce] Announcement; DirectoryStorage
Fri, 24 May 2002 17:24:54 +0100
Announcing the first release in nearly two years of
DirectoryStorage - a ZODB storage which keeps its data in a directory
containing many files; one file per revision per object.
Current status: pre-alpha. I am not yet using this in production.
This is the first release made by myself, based on the work started by
Available from CVS from http://sourceforge.net/projects/dirstorage
* A ZODB Storage which uses one file per revision of an object.
* A very simple file format. Your data is not locked away inside
an unfamiliar, opaque database.
* Use familiar filesystem tools for maintaining the database.
* Take an incremental backup using tar.
* Make crucial persistent objects immutable using file permissions
* Replication using rsync
* Support for filesystems which are most efficient with many
files in one directory (such as reiserfs), and also for filesystems
which are not.
* Support for filesystems with posix semantics. Support for win32
semantics requires a volunteer.
* Robust transactions, using a journal.
* Full.py: A storage which supports undo (but not versions, yet).
It needs occasional packing to remove unreachable objects and old
revisions of reachable objects (like FileStorage)
* Minimal.py: A storage which does not support undo. Packing is needed
to reclaim the space used by deleted objects. (packing not yet
* Constant memory usage, even during packing. With the right fileystem
I believe this makes DirectoryStorage the most scalable Storage
* Snapshot mode. After entering snapshot mode, the main database
directory is a self-consistent, up to date, read-only snapshot of
the storage state. Zope does not lose read/write access to the
Storage; writes are spooled in a secondary directory. This is ideal
for taking a backup of the database state without shutting
* Good redundancy of data. All object state (optionally) carries an md5
checksum. A storage checking tool is planned