amazon have just released ebs, the final piece of technology that makes their ec2 platform really viable for running lamp stacks stuck as drupal.
ebs, the "elastic block store", provides sophisticated storage for your database instance, with features including:
- high io throughput
- data replication
- large storage capacity
- hot backups using snapshots
- instance type portability e.g. quickly swapping your database hardware for a bigger machine.
amazon are quickly rectifying these problems, and recently announced elasic ip addresses; a "static" ip address that you own and can dynamically point at any of your instances.
today amazon indicated that persistent storage will soon be available.
in this article we get a sense of lamp performance on ec2 by running a series of benchmarks on the drupal cms system. these benchmarks establish read throughput numbers for logged-in and logged-out users, for each of amazon's hardware classes.
we also look at op-code caching, and gauge it's performance benefit in cpu-bound lamp deployments.
the previous article showed you how to set up jmeter and create a basic test. to produce a more realistic test you should simulate "real world" use of your site. this typically involves simulating logged-in and logged-out users browsing and creating content. jmeter has some great functionality to help you do this.
when making scalability modifications to your system, it's important to quantify their effect, since some changes may have no effect or even decrease your scalability. the value of advertised scalability techniques often depends greatly on your particular application and network infrastructure, sometimes creating additional complexity with little benefit.
apache jmeter is a great tool to simulate load on your system and measure performance under that load. in this article, i demonstrate how to setup a testing environment, create a simple test and evaluate the results.
clearly guardians shouldn't be used as a crutch for a badly configured system. used appropriately, however, they can decrease downtime due to unexpected events or administrator-error.
in this article, i describe how to implement, install and configure a guardian using a lightweight bash script. i go on to describe how to watch over your lamp install using this guardian. please note that all code and configurations have been tested on debian etch but should be useful for other *nix flavors with subtle modifications.
if you've setup a clustered drupal deployment (see scaling drupal step three - using heartbeat to implement a redundant load balancer), a good next-step, is to scale your database tier.
in this article i discuss scaling the database tier up and out. i compare database optimization and different database clustering techniques. i go on to explore the idea of database segmentation as a possibility for moderate drupal scaling. as usual, my examples are for apache2, mysql5 and drupal5 on debian etch. see the scalability overview for related articles.
i got some good feedback on my dedicated data server step towards scaling. kris buytaert in his everything is a freaking dns problem blog points out that nfs creates an unnecessary choke point. he may very well have a point.
having said that, i have run the suggested configuration in a multi-web-server, high-traffic production setting for 6 months without a glitch, and feedback on his blog gives example of other large sites doing the same thing. for even larger configurations, or if you just prefer, you might consider another method of synchronizing files between your web servers.
install.php, you were right. your bum was hanging squarely out of the window, and you should probably consider beefing up your security.
drupal's default exposure of files like
cron.php present inherent security risks, for both denial-of-service and intrusion. combine this with critical administrative functionality available to the world, protected only by user defined passwords, broadcast over the internet in clear-text, and you've got potential for some real problems.
when the times comes for scalability. moving of of the garageif you are lucky, eventually the time comes when you need to service more users than your system can handle. your initial steps should clearly focus on getting the most out of the built-in drupal optimization functionality, considering drupal performance modules, optimizing your php (including considering op-code caching) and working on database performance. John VanDyk and Matt Westgate have an excellent chapter on this subject in their new book, "pro drupal development"
once these steps are exhausted, inevitability you'll start looking at your hardware and network deployment.