Sometimes when copying files between drives I see the speed claimed at 500MB/s or so for a second or two before dropping to a more believable level for spinning hard drives, is it just copying to memory? Does this behavior change based on how much ram you have free?
The drives themselves have a buffer cache which you are initially filling up. Then the write queue is actually taking the cache and beginning to write to disk.
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And the cache is really fast, which is why you see the sudden burst of speed and then it levels off. What you see after that is the drives actual throughput.
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