Hi @huyvl3-fptcloud,
Hope your question is still relevant; I had taken the exam recently and I did not use the -K option when I formated a partition and everything was fine.
Also based on the RHEL documentation: "Block discard operations allow SSDs to optimize garbage collection routines, and they can inform thinly-provisioned storage to repurpose unused physical blocks."
I think that this option is usefull when you prepare a system to be used in production with high count of I/O operations, something like a DB server with SSD storage.
In an exam environment I do not think that the -K option will do much.
I hope this helps.
Regards.
Red Hat
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