Take the 2-minute tour ×
Database Administrators Stack Exchange is a question and answer site for database professionals who wish to improve their database skills and learn from others in the community. It's 100% free, no registration required.

It seems like our DB server is doing garbage collection at a increasingly faster rate, which seem normal since it's growing. What's a good rule of thumb of when to switch to a bigger instance, I'm not a DBA and have no frame of reference. It seems to be doing garbage collection once every 2-3 days now whenever there's only 100mb left.

enter image description here

The server itself has 1.7GB of RAM.

share|improve this question

2 Answers 2

Just ran across this question, and can give you a couple of suggestions.

If you're trying to gauge when to move to a bigger instances (vs. increasing the size of the databases) when you're getting close to hitting some sort of resource limit: Memory, I/O and CPU all have the ability to limit your performance.

The symptom you mention in the question may be a symptom that you're using more and more memory - memory used for cache & buffers are being reclaimed for other uses. Upgrading to a large instance type will increase the amount of available memory.

The chart that Rolando posted should give you a good guideline as to the number of available connections - if you're hitting those limits, then it's time to upgrade. Available connections are directly related to available memory, so hitting connection limits means you should upgrade.

If your CPU is averaging > 50% or so, you might want to start planning on an upgrade.

Finally, if you see consistently high I/O you may want to consider a larger instance (generally, the more powerful the instance the better the I/O) or using provisioned IOPS.

share|improve this answer

Before you switch server models, you need to know what differences there in configuration

I sat down and carefully looked over all default MySQL settings that would normally be written in a my.cnf. All are values are the same with the exception of two

Amazon set the following values based on server model

MODEL      max_connections innodb_buffer_pool_size
---------  --------------- -----------------------
t1.micro   34                326107136 (  311M)
m1-small   125              1179648000 ( 1125M,  1.097G)
m1-large   623              5882511360 ( 5610M,  5.479G)
m1-xlarge  1263            11922309120 (11370M, 11.103G)
m2-xlarge  1441            13605273600 (12975M, 12.671G)
m2-2xlarge 2900            27367833600 (26100M, 25.488G)
m2-4xlarge 5816            54892953600 (52350M, 51.123G)

For more information see my past posts on MySQL in Amazon RDS

share|improve this answer
    
It doesn't seem like this answers my question. I'm trying to understand when garbage collection and memory usage becomes a problem, not so much how to deal with it. I don't currently know if the garbage collection the DB is doing once every 2-3 days is healthy and at what time I should be concerned it's unhealthy, I would like to have some idea before it actually becomes an issue. How to fiddle with settings to free up memory seems like a separate issue, although I welcome the suggestions. –  Kit Sunde Oct 12 '12 at 19:28
2  
@KitSunde I think Rolando is indirectly trying to answer what you aren't asking - the title says "when should I upgrade" and he's basically saying upgrading won't address the memory issue, I think (though I am not a SME on this topic) –  JNK Oct 12 '12 at 20:28
    
@JNK Where does it say that upgrading isn't going to solve a memory issue? It's saying "here's some things you should know about RDS". I'm not stating I have a memory issue right now, my question is about finding out how to judge when to upgrade something before it's a problem. I could calculate when it'll spend more time garbage collecting than doing any actual work and find a sweet spot for upgrading (or tuning) my server, but I'm sure someone with more experience would have a simpler way of judging these things. I'm not sure if my question is unclear, I'll happily take edit suggestions. –  Kit Sunde Oct 12 '12 at 21:55

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.