Buy vs Build your Monitoring System

At the excellent London Devops meetup last week I asked what was apparently a controversial question:

should you just use software as a service monitoring products rather than integrate lots of open source tools?

This got a few people worked up and I promised a blog post.

Note that I wrote a post listing lots of open source monitoring tools not that long ago. And I’ve been to both the Monitorama events about open source monitoring. And have a bunch of Puppet modules for open source monitoring tools. I’m a fan of both open source and of open source monitoring. Please don’t read this as an attack on either, and particularly on the work of awesome people working on great open source monitoring products.

Some assumptions

  1. No one product exists that does everything. I think this is true for SaaS as much as for open source.
  2. Lets work with about 200 hosts. This is a somewhat arbitrary number I know, some people will have more and others less.
  3. If it saves money we’ll pay yearly, rather than monthly or hourly.
  4. We could probably get some volume discounts from some of the suppliers, but we’ll use list prices for this post.

Show me the money

So what would it cost to get up and running with a state of the art software as a service monitoring system? In order to do this we need to choose our software. For this post that means I’m going to pick products I’ve used (sometimes only a bit) and like. This isn’t a comprehensive study of all the alternatives I’m afraid - though feel free to write your own alternative blog posts.

How much!

In total that all comes to $35,080 (£20,922) per month, or $420,960 (£251,062) per year.

Now the first reaction of lots of people will be that’s a lot of money and it is. But remember open source isn’t free either. We need to pay for:

I think people with the ability to build software tend to forget they are expensive, whether as a contractor or as a full time member of staff. And people without management experience tend to forget costs like insurance, rent, management overhead, recruitment, etc.

And probably more important than these for some people we need to consider:

The time needed to put together a good monitoring stack based on for instance logstash, kibana, riemann, sensu, graphite and collectd isn’t small. And don’t forget the number of other moving parts like redis, rabbitmq and elasticsearch that need installing configuring and maintaining. That probably means compromising in the short term or shipping later. In a small team how core is building your monitoring stack to what you do as a business?

But I can’t use SaaS

For some people, using a software as a service product just isn’t going to cut it. Here’s a list of reasons I can think of:

I think everything else is a cost/benefit issue or personal preference (or bias). Happy to add more to that list, but I don’t think it’s a very long list.


I’ve purposefully not talked about the quality of the tools here, just the cost. I’ve also not mentioned that it’s likely not an all or nothing decision, lots of people will mix SaaS products and open source tools.

Whether taking a SaaS approach will be quicker, cheaper or better will depend on your specific business context. But try and make that about the organisation and not about the technology.

If you’ve never used the current crop of SaaS monitoring tools (and not just the one’s mentioned above) then I think you’re missing out. Even if you stick with a mainly open source monitoring stack you might look at your tools a bit differently after you’ve experimented with some of the commercial competition.