When NTFS compression is not a so brilliant idea.
I was running low on disk space, and I had virtual machines that took up large disk space while they are actually sparse inside. So, I decided to compress them. It worked great, their disk space was reduced significantly. But when I tried to use one of the virtual machines, it was painfully slow. Things that should take a few seconds took multiple minutes. The slightest disk changes took enormous amounts of time, and the CPU usage went crazy high. I couldn’t bear it for a long time, and I had nothing but the compression to blame. I uncompressed the machine and tried using it again and it worked extremely well!
It turns out that NTFS compression is not a very good idea for huge files that you plan to modify. I think things would have been just fine if the files were read only. So, the next time you consider compressing your file-system, do it on a per folder/file basis.