Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

imacken

macrumors 65816
Original poster
Feb 28, 2010
1,232
127
When I run BlackMagic Disk Speed Test on my Samsung D3 external USB3.0 drive, I get read and write speeds of 120Mb/s! My iMac late 2015 supports USB3.0, so why should that be?
 

Jimios

macrumors member
Nov 7, 2015
47
31
This is a pretty normal speed for a HDD, especially if it's 5400rpm. Your speed in this case is limited by the HDD rather than the interface.
 

Samuelsan2001

macrumors 604
Oct 24, 2013
7,729
2,153
When I run BlackMagic Disk Speed Test on my Samsung D3 external USB3.0 drive, I get read and write speeds of 120Mb/s! My iMac late 2015 supports USB3.0, so why should that be?

Because thats how fast HDD's are (well 5400rpm ones anyway the 7200rpm run to about 180Mb/s).
 

imacken

macrumors 65816
Original poster
Feb 28, 2010
1,232
127
Thanks for your help. Supposedly a 7200 in the Samsung, but.....
 

tyche

macrumors 6502
Jul 30, 2010
413
65
115-120Mb/s is fast. That's already showing 7200 rpm disk speeds. That's why SSD and especially pcie versions are so awesome.
 

m85476585

macrumors 65816
Feb 26, 2008
1,226
4
The speed depends more on the density of data on the platters than on the spin speed. A 1TB 5400RPM disk will be much faster than something like a 160GB 7200RPM disk. Random seek might take slightly longer on the 5400 RPM drive.

120MB/sec is fast for a spinning disk. A few years ago (maybe around 2010), people couldn't even comprehend that a disk could saturate USB 2.0 (around 35MB/sec) meanwhile my 1TB disks were showing 80-100MB/sec on eSATA. USB3.0 takes away a big bottleneck, but now the disk is the main limitation.
 

jerwin

Suspended
Jun 13, 2015
2,895
4,651
When I run BlackMagic Disk Speed Test on my Samsung D3 external USB3.0 drive, I get read and write speeds of 120Mb/s! My iMac late 2015 supports USB3.0, so why should that be?
That would be awesome for a USB 2.0 drive, which would be limited to 48 MB/s, so it's definitely USB 3.0.

Still, Blackmagic shows my LaCie Minimus drive (7200 RPM) at 172 MB/190 MB, so perhaps the Samsung D3 isn't on the leading edge of spinning rust. However, this review

http://www.techradar.com/us/reviews...hdd-ssd/samsung-d3-station-3tb-1183543/review

says that 216MB/s and 203MB/s should be possible.

So there's possibly some other things going on.

Is it formatted as NTFS? HFS+? Is it encrypted?
 
Last edited:

imacken

macrumors 65816
Original poster
Feb 28, 2010
1,232
127
Thanks for that. It's formatted as HFS+ and not encrypted.
The review did say that those speeds were not seen in real-world tests', so, not sure.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.