Slow "Read" speeds on 2 new HDDs

CalfCanuck

macrumors 6502a
Original poster
Nov 17, 2003
551
0
I just finished installing 2 new WD drives in my 2008 MP (bays 3 & 4). I ran the diglloyd DiskTester fill-volume test to condition them, and got some strange results - the "Read" results on both drives lagged write by a huge margin.

Here's the 2 graphs, along with a sample from the Excel template (that matches early HDD tests from a few years ago).

I turned off Spotlight and Time machine before the tests, and actually re-ran the 3TB drive test twice with everything running in my Dock turned off. Any ideas what is going on?

1. WD Caviar Black, 2TB:
http://www.weitergehts.com/images/WD_Caviar_Black_2TB.png

2. WD Caviar Green, 3TB (for Time Machine).
]http://www.weitergehts.com/images/WD_Caviar_Green_3TB.png

3. Sample graph, from excel template:
http://www.weitergehts.com/images/Sample_graph.png

(Edit: 10.6.8, 18GB)
 
Last edited:

Spacedust

macrumors 6502a
May 24, 2009
934
95
I just finished installing 2 new WD drives in my 2008 MP (bays 3 & 4). I ran the diglloyd DiskTester fill-volume test to condition them, and got some strange results - the "Read" results on both drives lagged write by a huge margin.

Here's the 2 graphs, along with a sample from the Excel template (that matches early HDD tests from a few years ago).

I turned off Spotlight and Time machine before the tests, and actually re-ran the 3TB drive test twice with everything running in my Dock turned off. Any ideas what is going on?

1. WD Caviar Black, 2TB:
http://www.weitergehts.com/images/WD_Caviar_Black_2TB.png

2. WD Caviar Green, 3TB (for Time Machine).
]http://www.weitergehts.com/images/WD_Caviar_Green_3TB.png

3. Sample graph, from excel template:
http://www.weitergehts.com/images/Sample_graph.png

(Edit: 10.6.8, 18GB)
Seems to be ok. Mac Pro's doesn't have SATA/600 controller.
 

CalfCanuck

macrumors 6502a
Original poster
Nov 17, 2003
551
0
Seems to be ok. Mac Pro's doesn't have SATA/600 controller.
Interesting. So if I had used a SATA II drive instead, I would have gotten better performance? I had assumed backwards compatibility, but not a speed hit...
 

theSeb

macrumors 604
Aug 10, 2010
6,963
91
Poole, England
Interesting. So if I had used a SATA II drive instead, I would have gotten better performance? I had assumed backwards compatibility, but not a speed hit...
NO. There is no speed hit and SATA II is more than fast enough for a single HDD. I don't know exactly what type of files that test is using (small, large etc), but the results don't look like there is anything wrong. Everything looks perfectly fine.

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Seems to be ok. Mac Pro's doesn't have SATA/600 controller.
So what? A single HDD cannot saturate SATA II, so having SATA III will make no difference.
 

derbothaus

macrumors 601
Jul 17, 2010
4,060
4
Interesting. So if I had used a SATA II drive instead, I would have gotten better performance? I had assumed backwards compatibility, but not a speed hit...
You'd get the same performance on SATA1 actually. You need more than one HDD RAID'd to saturate SATA bus. (Some very fast exceptions) Like 1TB Raptor. SSD's are a whole other ballgame.
 
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