RelStorage is a drop-in replacement for FileStorage or ZEO that uses a relational database like PostgreSQL as the storage backend. It provides faster commits and concurrency compared to FileStorage by optimizing caching and storing blobs in the database. Setup involves adding RelStorage and a database driver like psycopg2 to a Plone buildout configuration and specifying the database connection details. Existing storages can be converted to RelStorage using zodbconvert.

1. RelStorage
Plone
Relational
Database
Storage
Backend

2. Overview
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Drop-in replacement for FileStorage or ZEO
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For PostgreSQL, MySQL, Oracle, SQLite
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settled: around for ~13 years
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Active development driven by Jason Madden:
Version 3 released 2019
Latest release 3.4.0 in October 2020

3. PostgreSQL the Cloud DB
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Kind of „Industry Standard“.
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Well supported by all big cloud providers:
AWS, Google, Azure, IBM, Heroku, ...
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Easy to install in private clouds (or local):
Docker, Kubernetes, ...
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Very well maintained and thriving development
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Scaling solutions available

4. Advantages
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Fast, parallel commits, better
concurrency, shorter locks
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Optimized per process caching
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Blobs in database
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Optional history free

5. Usage: Setup
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„plone.recipe.zope2instance“ buildout support
minimal example
[instance]
eggs +=
RelStorage
psycopg2
sharedblobs = false
rel-storage =
type postgresql
dsn dbname='plone' host='localhost' user='plone' password='secret'
keep-history false

6. Usage: Caches
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additional client side caches
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shared between all threads of process
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Optional compressed
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Parameters to limit size, object count and
max-size of objects in this cache

7. Converting from FS or ZEO
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„zodbconvert“ converts from any storage
to another, like from ZEO to RelStorage
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Needs configuration file providing
connections to both storages
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Also converts blobs if needed

8. Packing
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ZODB keeps old transactions, so packing
is needed
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In history free mode only deleted objects
need to be cleaned up (DB bloats less)
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RelStorage provides a fast „zodbpack“

9. Versions and Blobs
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RelStorage 3.x is Python 3 only and runs
with Plone 5.2+ - Blobs should be stored
in RelStorage
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RelStorage 2.x is for Plone 5.0-5.1.x,
blobs should not be stored in DB, except
for Oracle backends.

10. Personal Note
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I use RelStorage today for all my live
deployments
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Use it since v.1.6 with Plone 4.3
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Never had problems
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Blazing fast
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DevOps/Sysadmins love it