The customer experienced huge Redis memory usage when using it as a handler for persistence cache. Therefore, some changes to Stash Redis driver are necessary, to make using igbinary serializer and lzf compression possible.

Instructions for QA:
To be able to test the changes introduced in this ticket, you have to follow the steps listed below. Please follow the order to avoid complications:

1. Install igbniary PHP extension*
2. Install lzf PHP extension*. Please say no to installator question about sacryfing speed for better compression.
3. Install redis PHP extension*. During the installation, you don't have to enable igbinary and lzf since these are used on the pure PHP side, but you can enable them and threat it as a separated test case.
4. Set-up Redis instance. I think, that the easiest way to do it is to set-up a docker container.
   1. docker run -itd --name ez-redis -p 6379:6379 redis:latest
   2. After few seconds Redis instance should be available under 6379 port on your localhost.
5. Configure eZ Platform to use new configuration. These settings aren't siteaccess aware. You can test different scenarios, for example with igbinary but without lzf and so on.
   ezplatform.yml

   ezpublish:
       stash_cache:
           igbinary: true
           lzf: true
   

6. Do some typical operations (create/update/move etc.) in the backoffice as well as on the frontend.

^* - all of these extensions can be installed by PECL. This is the easiest way to do it:

1. pecl channel-update pecl.php.net
2. pecl install _package_name_