Certain ZEO server errors could cause a client to get into a state
  where it couldn't commit transactions.
  https://bugs.launchpad.net/zodb/+bug/374737

  Savepoint blob data wasn't cleaned up after a transaction abort.
  https://bugs.launchpad.net/zodb/+bug/323067

  When committing transactions involving blobs to ClientStorages with
  non-shared blob directories, a failure could occur in tpc_finish if
  there was insufficient disk space to copy the blob file or if the
  file wasn't available.  https://bugs.launchpad.net/zodb/+bug/224169

Now link/copy file when storeBlob is called.

  Objects defining _p_deactivate methods that didn't call base methods
  weren't loaded properly. https://bugs.launchpad.net/zodb/+bug/185066

for objects that don't use slots, which are the vast majority of
persistent objects.

while cleaning up removed blob files.

Also refactored the code slightly for clarity.

(https://bugs.launchpad.net/zodb/+bug/400775)

Also, stop producing legacy PersistentMapping state, while still
accepting it.

Simplified the file-storage configuration a bit.  Eliminated
duplication of defaults between the Python and ZConfig interfaces.

- Fixed vulnerabilities in the ZEO network protocol that allow:

CVE-2009-0668 Arbitrary Python code execution in ZODB ZEO storage servers
  CVE-2009-0669 Authentication bypass in ZODB ZEO storage servers

- Limit the number of object ids that can be allocated at once to
  avoid running out of memory.

- The "lawn" layout was being selected by default if the root of
  the blob directory happened to contain a hidden file or directory
  such as ".svn".  Now hidden files and directories are ignored
  when choosing the default layout.

- BlobStorage was not compatible with MVCC storages because the
  wrappers were being removed by each database connection.  There
  was also a problem with subtransactions.  Fixed.

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- Simplified the setup script in hopes of working with bdist_rpm.

- Fixed the setup test command.  It previously depended on private
  functions in zope.testing.testrunner that don't exist any more.

default to local host.

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- ZEO protocol 2 support was broken.  This caused very old clients to
  be unable to use new servers.

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- ZEO client threads were unnamed, making it hard to debug thread
  management.

to closs connection.  This showed up on windows but not linux or mac
os x. I wonder why.

cache and cleaning the cache.