In [version 2.14 installation guide|http://example.com], here is documented as environment requirement for AWS.

If you are using an Amazon Simple Storage Service (Amazon S3) bucket for content management system (CMS) storage:

Persistent volumes

・3 RWO (ReadWriteOnce) persistent volumes for Redis and MySQL persistence.

Storage

・Amazon S3 bucket
・NFS

Regading persistent volumes, this still says

・3 RWO (ReadWriteOnce) persistent volumes for Redis and MySQL persistence.

but this should be:

・4 RWO (ReadWriteOnce) persistent volumes for Redis, MySQL, and System-searchd persistence.

i.e. PV for system-searchd is still missing in this description.