I have begun to notice major system performance hits when doing an update to any Unreal Engine versions I have. This appears to be the case on several computers including my high performance desktop machine. Other applications become unresponsive for long periods. For example I tried to open up a system administrator instance of Powershell. It took approximately five minutes before the system grayed out my monitors to bring up the UAC screen and about 2-3 minutes before the permission screen even came up from that point. Several minutes after approving the process to make changes to my system I finally got a Powershell window but after about five more minutes of no command line prompt I closed the window (shockingly that wasn’t affected). My mouse cursor freezes frequently. Even when I’m running a major update of Windows 10 I rarely have performance issues quite this bad. I have 16GB of RAM, an i7 Intel Skylake CPU, and a 1TB HDD for my OS and a 4TB HDD for my data. I have a 1GB, full duplex, fiber optic internet connection. Without further evaluation with other tools I can only surmise is that the launcher is locking resources on the drive it is running on and not releasing locks after using them. Worse, it’s locking more than it actually needs to accomplish its tasks. For large engine updates my system is almost bricked until the update is done. For the next update I plan to use an advanced tool to monitor exactly what it is doing to my system that is so hurtful and unnecessary.
No response from anybody on this topic? Seriously. My system comes to a crawl with any updates/installs using the launcher. Please explain why typing text is reduced to about five seconds for a character to appear. Why I can’t minimize windows for several minutes, etc. My system is not low-end. There is no excuse for this.
If your HDD is capped at 100% then CPU and RAM won’t help that much either.
Not sure if this would solve this exact problem, but… in 2018 the SSD is the best possible hardware upgrade. Speeds up the system and all of the heavy applications using a hard drive a lot.
I never experienced such issue on SSD. Almost everybody working on modern engines uses SSD, it’s a pain without it.
Another cause could be a malfunctioning RAM. It oftens leads to short or long periods of unresponsiveness, but it’s the last place we would look for 
While I’m aware of the system speed increases of an SSD but that is not the problem here. This is not a simple matter of I/O read/write speeds. No software installation other than OS updates should bring the system down to the point that simply typing has the appearance of characters taking up to a minute (or longer) to actually appear. It should not block the Task Manager (or any other software) from launching for 10 minutes or more (seriously!). The best I can tell is that the Launcher is either locking the drive or giving itself priority to its read/writes over every other process on the system - including over the OS. Maybe it’s locking registry access.
I’ve already checked the integrity of my RAM and drives; they are fine. I’ve run OS diagnostics, etc. This is a recent problem with the Launcher.