Well, not the fastest drive but ok, you need to read 0.025% of plotfile on every round (4096 scoops, One Scoop needs to be read per block) that is in your case ~670MB per round, divided by 26sec. we are at ~25MB/s.
Like mentioned above, you could try optimizing ...
Also check: https://bchain.info/BURST/tools/overlap it will show you needed drive seeks, very useful.
After set stagger in there equal to number of nonces, and you will get an idea what improvements optimizing can be.
324324234324324_0_1000000_100 -> 10000 disk seeks per Scoop (80 seconds @ 8ms)
324324234324324_0_1000000_1000000 -> 1 disk seeks per Scoop (0 seconds @ 8ms)