how does windows azure platform scale for my app?

问题:

Just a question about Azure.

Yes, I know roughly about Azure and cloud computing. I will put it in this way:

say, in normal way, I build a program listening to a TCP port. I run this server program in a server. I also build a client program, which connects to the server through specified port. Once a client is connected, my server program will compute some thing and return to the client.

Above is the normal model, or say my program's model.

Now I want to use Azure. I want to use because my clients are too many, let's say 1 million a day. I don't want to rent 1000 servers and maintain them. ( just a assumption for the number of clients)

I have looked at the Azure pricing plan. It say about CPU and talks about small, median, large instances.

I don't know what they mean. for e.g., in my above assumed case, how many instances do I need? or at most I can get from azure for extra large (8 small instances?)

How does Azure scale for my program? If I choose small instance (my server program is very little, just compute some data and return to clients), will Azure scale for me? or Azure just gives me one virture server and let it overload?

Please consider the CPU only, not storage or network traffic.

回答1:

You choose two things: what size of VM to run (small, medium, large) and how many of those VMs to run. That means you could choose a small VM (single processor) and run 100 "instances" of it (100 VMs), or you could choose a large VM (eight processors on the same server) and run 10 instances of it (10 VMs).

Today, Windows Azure doesn't automatically adjust your scale, so it's up to you to use the web portal or the Service Management API to increase the number of instances as your need increases.

回答2:

One factor to consider is if your app can take advantage of multi-core environments - multi-thread, shared memory, etc. to improve its scale. If it can, it may be better to use 5 2x core (i.e. medium) VMs than 10 1x core (small) VMs. You may find in some cases that 2 4x core VMs perform better than 5 2core.

If your app is not parallel/multi-core, then you could just do some 'x' number of small VMs. The charges are linear anyway - i.e. a 2core VM is twice the cost of a single core.

Other factors would include the scratch disk size & memory available in the VM.

One other suggestion - you may want to look into leveraging the Azure queues (i.e. have the client post to the queue and the workers pull from there). This would allow you to transparently (to the client) increase/decrease the workers w/out worrying about connections, etc. Also, if a processing step failed and crashed your instance the message would persist and be picked up by one of the others.

回答3:

I suggest you also monitor, evaluate, and perfect the results of your Azure configuration.

For "Monitoring Applications in Windows Azure" (and performance) please reference http://channel9.msdn.com/learn/courses/Azure/Deployment/DeployingApplicationsinWindowsAzure/Exercise-3-Monitoring-Applications-in-Windows-Azure/

There is also a good blog entry titled "Visualizing Windows Azure diagnostic data"

回答4:

Check out http://www.paraleap.com - simple service for automatically adjusting number of instances that you have according to demand.