Thank you Ross Patterson for clear directions!
However after following the above instructions, and a migration
apparently happening - I can look in the blobstorage directory for the
site and see what looks like the new arrangement of blobstorage - I get
errors on all file objects, one way or another. Images are now
missing/broken on pages; files such as PDFs etc. return an error with
traceback always ending in:
Module zope.tales.expressions, line 217, in __call__
Module Products.PageTemplates.Expressions, line 155, in _eval
Module Products.PageTemplates.Expressions, line 117, in render
Module plone.app.blob.field, line 129, in get_size
Module plone.app.blob.utils, line 52, in openBlob
Module ZODB.Connection, line 860, in setstate
Module ZODB.Connection, line 922, in _setstate
Module ZEO.ClientStorage, line 1020, in loadBlob
POSKeyError: 'No blob file'
I have put back in place the 'lawn' blobstorage for now and the site is
fine again. It needs to stay fine, as it is a county government site
with lots and lots and LOTS of public documents on it.
I would like to migrate to 'bushy' blobstorage, if it is truly important
to do so. However I don't know what to do next to troubleshoot my situation.
I've found some posts about the POSKeyError but they are all, so far,
about corrupted situations of various kinds which I am pretty sure I
don't have. I've not found anything yet relevant to the migration script
producing a 'bushy' migration result that is broken like this.