4.1. Hardware ConsiderationsManaging a reasonably large network requires an NMS with substantial computing power. In today's complex networked environments, networks can range in size from a few nodes to thousands of nodes. The process of polling and receiving traps from hundreds or thousands of managed entities can be taxing on the best of hardware. Your NMS vendor will be able to help you determine what kind of hardware is appropriate for managing your network. Most vendors have formulas for determining how much RAM you will need to achieve the level of performance you want, given the requirements of your network. It usually boils down to the number of devices you want to poll, the amount of information you will request from each device, and the interval at which you want to poll them. The software you want to run is also a consideration. NMS products such as OpenView are large, heavyweight applications; if you want to run your own scripts with Perl, you can get away with a much smaller management platform. Is it possible to say something more helpful than "ask your vendor"? Yes. First, although we've become accustomed to thinking of NMS software as requiring a midrange workstation or high-end PC, desktop hardware has advanced so much in the past year or two that running this software is within the range of any modern PC. Specifically, surveying the recommendations of a number of vendors, we have found that they suggest a PC with at least a 2 or 3 GHz CPU, 512 MB to 1 GB of memory, and 1-2 GB of disk space. Requirements for Sun SPARC and HP workstations are similar. Let's look at each of these requirements:
Let's think a bit more about how long-term data collection affects your disk requirements. First, you should recognize that some products have only minimal data-collection facilities, while others exist purely for the purpose of collecting data (for example, MRTG). Whether you can do data collection effectively depends to some extent on the NMS product you've selected. Therefore, before deciding on a software product, you should think about your data-collection requirements. Do you want to do long-term trend analysis? If so, that will affect both the software you choose and the hardware on which you run it. For a starting point, let's say that you have 1,000 nodes, you want to collect data every minute, and you're collecting 1 KB of data per node. That's 1 MB per minute, 1.4 GB per dayyou'll fill a 40GB disk in about a month. That's bordering on extravagant. But let's look at the assumptions:
Seriously, it's hard to estimate your storage requirements when they vary over two or three orders of magnitude. But the lesson is that no vendor can tell you what your storage requirements will be. A gigabyte should be plenty for log data on a moderately large network, if you're storing data only for a reasonable subset of that network, not polling too often, and not saving too much data. But that's a lot of variables, and you're the only one in control of them. Keep in mind, though, that the more data you collect, the more time and CPU power will be required to grind through all that data and produce meaningful results. It doesn't matter whether you're using expensive trend-analysis software or some homegrown scriptsprocessing lots of data is expensive. At least in terms of long-term data collection, it's probably better to err by keeping too little data around than by keeping too much. |