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One common topic of discussion is whether to upgrade or replace a server. There are a number of factors that go into making this decision. The first is cost -- most data centers don't have an unlimited budget, so administrators need to consider which option is more cost-effective. Although virtualization helps administrators use their hardware resources more efficiently, servers are often expensive, making them difficult to simply replace. Upgrading servers purely for the sake of change is costly as well, and can cause issues in your data center. As a result, the first step to making an informed decision between replacing and upgrading servers is to monitor your preexisting data center.
It's always important to assess the effects of any change to your environment. When it comes to upgrading and replacing hosts in a virtual environment, having the ability to replace them is the ideal scenario, however, you can avoid an expensive purchase if you can add additional memory to memory constrained hosts. That said, if your servers are CPU-constrained and do not have additional CPU sockets available, replacing the hosts is likely your only option. Replacing hosts is substantially more expensive than simply adding memory, but keep in mind that price is not the only factor to consider when choosing whether to replace or upgrade; you must also consider growth curve and performance.
The goal is longevity
When considering upgrading servers, ask yourself, "How long will it be applicable?" Upgrading memory or storage in an environment is only beneficial if the upgrade lasts until your next budget cycle or a planned replacement. Otherwise, all you've done is fill a shortage gap that will need to be addressed again in the near future, most likely during an unplanned cycle. This stopgap measure can cost you more in the long run, especially if you have to replace equipment -- the cost of the replacement combined with the cost of the original upgrade can amount to a hefty sum. Growth curves can be tricky to track because one large project can greatly affect normal growth trends. However, you can almost always depend on growth to trend upward.
Some people argue against buying replacements and are in favor of making equipment last longer because they intend to move to the cloud. The cloud has existed in some form or another for many years now, but everything from costs to regulations to security has kept adoption rates lower than expected. That doesn't mean that the cloud won't eventually find its footing, but, in the meantime, you'll need to keep your data center around.
Upgrading servers affects performance
Another thing to consider before upgrading servers is what an upgrade will do to overall system performance and reliability. For example, moving a server from spinning disk drives to a solid-state drive can have a tremendous effect on performance if the server is fully capable of using the new hardware. If the server isn't capable, upgrading may still yield a performance boost, but a much smaller boost than anticipated. The other concern is that improving one aspect of the system might burden the parts that are now trying to keep up with the updated component. This is typical of introducing upgrades to older systems. This kind of change can even affect application behavior and create new bottlenecks in the system.
Although the reliability of new components in a system generally isn't a major concern, you should still be cognizant of the overall lifespan of the equipment you're upgrading. Equipment nearing end-of-life for support should not be upgraded with the intention of running outside of its supported lifecycle. Even equipment on extended maintenance contracts must be closely evaluated, as increasing maintenance costs year over year may be far greater than the cost of replacing the equipment.
While many IT folks would always prefer to go with new equipment, upgrades are a necessary part of data center life. The key to a successful upgrade has more to do with its business impact, growth, performance impact and lifespan of the original equipment than the technology itself. Keep all of this in mind and you should have no problem choosing between upgrading and replacing elements of your data center.
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