Kali LivePersistent-USB - how fast should Pendrive be?

Hi guys,

I am writing, because I want to have Kali LivePersistent USB, and I really don't know how fast my Pendrive should be.

Some ppl say that 80MB/s writing speed is enough, but I have a pretty cool offer for 170 MB/s one.
The problem is -> My HDD speed is 100MB/s (don't have the SDD one). Will my Pendrive 170MB/s be downgraded to 100 MB/s when launched Kali or 100 MB/s will be only for HDD-Pendrive communication and doing other things (like "count from 1 to 1,000,000,000,000 and write it into Pendrive) will be taken directly from RAM and then the writing speed will be 170 MB/s ?


I really need help ;(

flash will work at its max speed, copy speeds will be whatever is the bottleneck in this case HDD, so even though it might cache to ram at 170mb/s from flash, it will only copy at HDDs max speed after it reaches the cache limit.

kali will read/write to and from flash drive at flash drive's speeds, HDD has no influence to bottleneck speeds within the flash drive.