Cluster Suggestion (LAMP)

[Afox]

Hello,

if you had unlimited ressources, what would be the ideal setup for a high performance LAMP server cluster that could require a lot of storage capacity? You can also expect a lot of PHP/mysql work.

Questions I have: what storage should be used? If you have e.g. one node running a load balancer VM, one or more nodes running mysql-server VM, one or more nodes for other VMs (internal stuff) should they all use the same shared storage? Or should e.g. mysql-VM run on a diffent storage type? Is Ceph faster than other shared storage solutions?

I´d prefer Apache Webserver. All disks could be SSDs.

I am happy for any hint from reality.

Regards,

Afox

 

[LnxBil]

A simple answer is not possible :-(

If you application uses local files (e.g. images or stuff) and you want to serve from all Apache instances, you need to have a shared storage or copy the files and sync them on every change. A real MySQL cluster can IMHO not have a shared database, that's only possible with the other database Oracle is selling and you need a RAC for that.

For all databases, you need to check the physical block size or your database against the filesystem it uses and against the backend storage in your virtualization environment and probably also your raid controller. Everything has to be aligned and tuned towards each other, e.g. if you use 8 KB block size in your database, it is best to have that as well in your filesystem (which is a bit trickier, two 4K blocks do not have to be near each other). The partitions on your guest have to be aligned, which is default on current Linux systems. The backend has to have 8K blocks as well and if you use raid, you'll normally have stripe sizes and stuff. RAID-5 or RAID-6 is also not the best for database because of the write penalty.

Technically, it will work without these things, but you can encounter write amplification resulting in terrible write performance. Best for high performance databases is still to have them on bare metal and cluster them. This is very easy with a "real" Oracle Database and RAC technology.