Vertical scaling is when you increase the power and capacity of a single server. Upgrades could include a more powerful CPU, adding memory, and increasing storage capacity. For example, you might have a server using a second-generation Intel Xeon Scalable processor. Vertical scaling could involve updating the CPU from 16 cores and 32 threads to 24 cores and 48 threads, as an example. Vertical scaling could also involve more obvious upgrades such as increasing the amount of server RAM, adding more and larger hard drives or SSDs to a RAID array, and so on.
Vertical scaling has an advantage in that you only need to worry about a single server: no additional network cards, IP addressing or routing problems, no further strain on server room power requirements, and no additional worries about heat buildup. Also, in some cases, costs might actually be lower for vertical scaling as you are not adding entire additional computers to your network, just internal components.
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