Re: To Cloud or Not to Cloud
Hi Brodsky,
It seems you are asking about creating and using an "elastic" highly-available infrastructure. What follows is my own opinion
- For building a UEC based cloud, you'd need at least 2 servers (or more). The following notes might be useful
http://open.eucalyptus.com/learn/InstallingECC
- A "cloud" like UEC, offers a scalable elastic infrastructure, however to utilize it, your application needs some intelligence, and your sysadmin processes too. SysAdmin processes need to evolve in order to be able to get a fresh machine, install it, register it, install apps, copy data take it to production all via automated scripts (or config management tools like puppet or chef or others). All that should be done in a few minutes. Let's go through an example. Assume you currently have 1 webserver and 1 DB server. Load increases a lot (slashdotted?) you need to spin up 10 additional web servers + 2 additional read-only DB replicas. Here's what you need
- You need 10+2 = 12 new virtual servers. UEC gives you that easily
- You need to "deploy" those 12 fresh machines into their "roles" of "web" servers and DB replica servers. UEC is not involved here. Your sysadmin processes and config management tools need to be ready to do this
- Your load balancer (if you don't have one you need to get one) should be configured to spread some the load to the new boxes. Again config management
- Your "application" needs to know how to work and utilize those 10 new web servers. i.e. it needs to scale, handle transactions, handle sessions ...etc This is an application problem. If your app cannot do that today, it might need to be re-written or modified at least
Also in cloud contexts, people don't normally target clustering/failover. If a virtual/physical server fails, your monitoring system should detect that, UEC should be asked to provide alternate servers, your tools should engage to deploy the new servers into production. Servers are in essence stateless. If a server wants to die, it can die, I can replace it anyday. That's the cloud spirit :) While the clustering spirit was, if a server wants to die, I won't let it
I hope this was useful
All the best
Re: To Cloud or Not to Cloud
Thanks for the detailed answer Kim0 :)