As with all technical things, measure twice, cut once. But how much time to spend measuring depends in large part on how complicated your environment is. There are a lot of factors that go into planning a server appropriately, such as heating and cooling, the physical machine that will be the server, and even how the server will be backed up.
You can spend an unlimited amount of money on a server. Or you can spend next to nothing and buy a used Mac mini on eBay. The scale of your purchase and the complexity of the deployment are two very independent concepts though. In this chapter, we’re going to look at, well, basically what you should buy before you get started installing that spiffy server of yours (and, importantly, whether you should buy something different than the shiny box you already have in your hands).
By default, Lion Server is installed from the Mac App Store on a computer that is already running Mac OS X Lion. The minimum requirements for the computer that you install Lion Server on will be the following:
64-bit Intel processor
2 gigabytes of RAM
10 gigabytes of available hard drive space
Access to the Mac App Store on the Internet
These settings are the minimum requirements for Lion Server, but most servers require far more resources. Resources such as hard drive space, memory, and even items that aren’t part of the server itself but are part of the ecosystem that acts to supplement it are important to plan for in advance. For example, if there isn’t any Internet access on the server before you sit down to install it, then you might need to take the server to a place that does have Internet access or plan on imaging the server using a traditional imaging solution before wasting time on what would be a failed installation.
One of the first factors to decide is how many servers you need. For most OS X Server environments, the answer is going to be one. But the impact that scale has on the rest of the options we cover throughout this chapter cannot be discounted.
For an environment with 5 to 10 users, as would be common with a typical home environment, any of the hardware mentioned previously will suffice whatever your needs may be, with one exception: hard drive space. We’ll discuss drive capacities later in this chapter, but for now we can consider a few indicators that you need to consider a second server (or more):
You have 300 or more users: One Mac Pro can typically run things like portable home directories for a good 300 users simultaneously.
System resources are getting crushed: Looking at the Activity Monitor shows overly high utilization in at least one category, although frequently in more than one.
Business stops when a server goes offline: Organizations can be severely impacted when a server goes offline. Most notably, if a web server cannot accept customer orders or a mail server is not available.
Although some general rules can be helpful, nothing is more useful in determining utilization statistics and planning for future purchases than monitoring software. There are a lot of monitoring software packages, including Lithium, Dartware’s Intermapper, and Nagios, all of which have specific tools for monitoring Mac OS X Servers.
No matter how many servers you elect to use, the next question to answer is what services to run. Anytime you get a shiny new piece of technology, it is tempting to enable everything that can be done with it. However, doing so with Lion Server will produce a server that runs more slowly than it should. Instead, plan ahead and know which services to enable before unboxing the product, and more specifically, which services to enable on each server.
Lion Server runs in a multimaster configuration. The directory services (explained more in Chapter 2) are effectively a master on each server. This means that any server that is a directory server acts as a master that replicates with the Open Directory Master.