Improve Performance OwnCloud 9, MySQL, php 5 on Debian Jessie

Well, I installed OC from repository, redis 2.8.17, php5.6.24
and mysql-server 5.5.52.
Owncloud works with redis, but it is still a bit slow in my opinion.
I'm testing with different option in config.php. Cpu is very high and it
seems, that the server needs a lot of time to make preview of pictures
(my first tests are with photos).
How much memory and cpu is recommend for Owncloud ? First I had 1024 MB Memory. Now I increase to 2048 and I think, it is a bit faster. But as I open picture gallery, CPU load is up to 80% for a short time. As I am using owncloud alone, it is no problem, but I would like share for example photos with my family and friends - so normally, there should be some more users use this function.
Are there maybe some other configs that can be recommend for a lot of users ? For that purpose I installed mysql and redis, as I thought, that is a good choice for a good performance.


previews in general takes a long time and performance.

Try first to update to PHP 7.0 which brings a lot of speed improvements comparing to PHP 5.x. Afterwards you can generic optimization guides for web applications and PHP applications (e.g. and so on.

There is nothing more than the suggestion above what you and we can do from user-side.