Massively incorrect drive read speeds

[Super Fast]

I have tried Defraggler on a few drives, and noted that sometimes, it is accurate. And matches Windows 7 file copy progress percentage.

But other times, it is off. And I mean wayyyy off!

 

I tested Defraggler on a friend's PC that was running v-e-e-e-r-r-r-y-y-y-y slooooowwww!

Windows XP on an 800 GB drive that had become out of alignment.

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Defraggler suggested 4 mb/s write speed, which was accurate. Windows 7 on my machine, connected to the drive externally via USB2 was also the same.

 

But then, after alignment, Windows suggested the drive was writing at close to 16 mb/s, or nearly 4 times faster. I put Windows 7 on his machine after a drive format, & Defraggler said the same as 7.

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This is where things get weird...

 

After setting up 64 Bit 7 on his machine, I ran defraggler to consolidate files, etc. Checked the write speed in 7, & it still showed 15-16 mb sec.

Defraggler, however, insisted the speed was about 28 to 35 mb/s

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To top things off, I then ran defraggler 2.08 on a 64 Bit laptop, & the drive speed checker said the drive was writing at 1.88 mb/s. PIO mode? NO! I tried file copy in 7, & it did over 100 mb/s for a few seconds, before it started slowing down to stabilize at around 50-60 mb/sec

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What gives? Why is Defraggler sooooo far off sometime, but other times so accurate?

[Alan_B]

But then, after alignment, Windows suggested the drive was writing at close to 16 mb/s, or nearly 4 times faster. I put Windows 7 on his machine after a drive format, & Defraggler said the same as 7.

An ultra deep low level drive format that totally disregards all track and sector identity markers, and rewrites every byte in every sector on every track,

or a Quick format or something in-between that might have omitted sectors/tracks that had never been used and might have escaped corrective alignment ?

 

If some tracks are less aligned than others, the speed measurements would depend upon which tracks were "randomly" chosen by the various speed tools.

[Super Fast]

I thought about that, Alan. I did a quick format.

 

However, I also partitioned the drive into 3 partitions, & checked them all to see what the read speeds were on all 3 drive partitions.

They were all the same speed reading, or very very close.

 

Then, I deleted the partitions & made a single large partition. If it were a sector problem, partitioning the drive would change the read speeds in one of the partitions.