There is no straightforward equation for Cloud Server to exactly predict what can be the right amount of RAM and CPU, here are some practical facts. Clearly know – if your Website has approximately 5K Posts, You get around 1800 Page Views per day, it is mandatory to use multiple server. Only caching will destroy a huge amount of computing power. It is a very bad idea to run one server with 2 GB RAM from our experience. Nearly every Cloud Server performs poorly due to disk I/O issues – yes, even on Rackspace with SSD – that is why dedicated servers are used when high redundancy is needed. Once the disk writing process spikes up, the system snowballs to a halt until it can recovered by forced hard reboot – one must measure the metrics, like in case of Rackspace, the user can use Rackspace Monitoring Agent to watch the consumption.
RAM and CPU Needed For Cloud Server to Run WordPress
If your website was simple HTML or used Perl or Python, you could easily use one 512 MB instance with the parameters. WordPress is quite poorly coded in PHP. PHP is never known to be very great programing language. Application server / Database Server is better replaced with a Cloud Database for better scalability. One 512 MB Database Server is more than enough for WordPress website as the caching Plugins writes the data (caching) on Web Server. The problem starts from the way PHP web software caches – it basically burns huge computing power. There is no WordPress Plugin which can logically cache only when there is less CPU consumption.
So, minimum recommend setup for a medium sized website running WordPress would be :
- One Cloud MySQL instance at least of 512 MB size
- One 2 GB server as master, virtual two cores are great to have
- One 1 GB server for replication
- CDN to serve static contents
- One loadbalancer in front
This is for a typical LAMP server ( read Apache web server ). If nginx is used, easily the requirements can be halved.
Caching Softwares Increases the Need of Higher RAM and CPU For Cloud Server to Run WordPress
From Varnish to WordPress Cache Plugin – all will ultimately suck both CPU and RAM to Cache. Remember that, when we SSH and work, the frontend continues to serve pages – we might use more CPU and RAM in addition to what a web server requires to run only WordPress.
If your website serve soft 404, Google Webmaster Tool might not report, but the reliability of your website decreases, logically Google bots will understand – your website will fail to handle a huge traffic. Honestly, you can check Free PaaS from RedHat OpenShift – they uses at east two gears for running WordPress. You can read a very nicely written article :
Obviously, for serious WordPress websites, there can be more softwares to run various stuffs – Podcast, some own developed software etc. These might increase more load. Unfortunately, even increasing resources can not make WordPress fail safe in front of sudden traffic surge. Auto Scaling like service from Rackspace can logically share the load. The problem with Auto Scaling and WordPress is of WordPress – allow time to cool down and write or publish post.