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Q: Wordpress optimization and caching
I'm installing a new Wordpress, but this time around WP highly-optimized, at first place I'm keeping an eye on CPU load, secondly on page opening speed, and finally comes RAM which is being less important to this case than CPU and page loading time. And I'm using Mysql for db.
So what WP plugin I should depend on for getting all pages and comments cached so that minimal Mysql queries, and hence free some load on cpu and i/o?
Any specific Mysql optimization recommended with WP to reduce memory?
Also, if Apache is used, any recommendation of modules? Any recommendation for threads no. optimization?
Yes I know that's so many, vast, and boring questions. So, most important to me for saving your effort, is: caching and WP plugins.
Thanks for any help (appreciate any) 
Comments
I have used DB Cache and also increased the "mysql-query-cache" on Mysql.
Another small change that has helped me before, is to have all static content in a directory or subdomain outside wordpress, this way you dont use php-resources.
Thanks thekreek, I'm not familiar with WP add-on so I look into real recommendation for the cache thing, I'm checking that one
Use W3-Total-Cache plugin for WordPress. It will help you a ton in caching.
I hope you're using an opcode cacher as well.
Get rid of Apache and use nginx. Make sure you're using a PHP opcode cache such as APC. Follow the tips here for reducing MySQL's memory usage (note that if you're using MySQL 5.5, you'll need to make some changes - particularly "innodb = OFF" and "default-storage-engine = MyISAM" instead of "skip-innodb"). These are, of course, general recommendations that can be applied to any web/database server.
Concerning Wordpress in particular, the only caching plugin I've ever used is WP Super Cache. Not that it's necessarily the best one, but I've found it to be sufficient.
@all: That's so helpful to me, going to try each, and thanks a lot guys
@NickM: Yes I've installed 5.5 and I've found that "skip-innodb" doesn't work anymore, but your trick seems to work, also by searching I've found "ignore_builtin_innodb" instead of "innodb = OFF", it's going to help a lot since it's eating close to 300 mb on OVZ worse than previous Mysql :X ..Thanks for the useful tips
If not running with openvz, using Innodb and keeping innodb_buffer_pool_size/available memory larger than your db size is a simple and useful way to optimize your wordpress application
@tinyX: Thanks for the tip, but I'm limited in RAM that's why the 300 mb innodb seems to eat in Mysql 5.5 is close to all what I expect for actually running the whole thing, and I'm using OpenVZ.
w3 total cache or wp super cache are both good options; I'm not sure you necessarily need to go to nginx (or lighttpd, etc.) but it's something to consider.