Slow SSD speeds

[snipedude90]

I recently installed a 120 GB OWC Mercury Electra 6G SSD into my secondary drive bay using the install kit from OWC. Using Blackmagic Disk Speed test I am only getting on average 100-150 mb/s writes and 150-180 mb/s read speeds. This is far from the 500+ advertised (and even the real world tests I've seen on YouTube). Does anybody have any idea as to why my speeds are so low? I do have the firmware upgrade that was released in 2011 to un-throttle the 6G SATA speeds.

I don't think it is simply the app because I used the same app on my 2012 Macbook Air and got 400+ mb/s sustained read/write speeds. Any advice on this would be appreciated.

 

[ConCat]

You sure it's not benchmarking the HDD?

 

[snipedude90]

You sure it's not benchmarking the HDD?

I had considered that, but its showing as being connected to the SSD. I benchmarked my HDD previously and the speeds are around 80 mb/sec r/w.

 

[ConCat]

I had considered that, but its showing as being connected to the SSD. I benchmarked my HDD previously and the speeds are around 80 mb/sec r/w.

Yah, those numbers are a bit high for a laptop HDD and far too low for a modern SSD. Definitely peculiar. I haven't the foggiest.

 

[snipedude90]

Update

Here are test results from Xbench as well. While the speeds are better than I am used to with an HDD, I didn't spend almost $200 and 2 hours of my time for such a marginal gain in performance, especially when others are getting much better speeds with the same hardware.

 

[ConCat]

I may have figured out the problem. It doesn't seem to be going any faster than SATA II would allow. What model of iMac do you have btw?

 

[kohlson]

What does About This Mac say about Link Speed or SATA version (1, 2, or 3)? With respect to performance, how does this translate to real work (not benchmarks). Faster starts? Saves? Compiles? I'd be interested to see if the SSD did not have a significant affect on these.

 

[BeeJee]

I may have figured out the problem. It doesn't seem to be going any faster than SATA II would allow. What model of iMac do you have btw?

SATA II goes faster.

 

[ConCat]

SATA II goes faster.

SATA II SSD benchmarks seem to not be much faster than what he's getting, his highest numbers anyway. Some of them are a bit lower than you'd expect, but there could be any number of reasons for that. I'd wager that his computer is operating at SATA II speeds.

 

[WilliamG]

SATA II SSD benchmarks seem to not be much faster than what he's getting, his highest numbers anyway. Some of them are a bit lower than you'd expect, but there could be any number of reasons for that. I'd wager that his computer is operating at SATA II speeds.

Not really true. 4 years ago I installed a 120GB OCZ Vertex in my MacBook Pro and also a 2009 iMac, both SATA II. I got over 225MB/s read and almost 200MB/s writes.

 

[snipedude90]

I may have figured out the problem. It doesn't seem to be going any faster than SATA II would allow. What model of iMac do you have btw?

OP here. It is a 2011 27" 3.4 ghz i7 with 16 gb of RAM.

The computer definitely "feels" faster but the performance numbers simply aren't there which is what bothers me. I'm at work until about 11:30 central time tonight. I'll check back then and provide any additional needed details. Thank everyone so far.

 

[ConCat]

Not really true. 4 years ago I installed a 120GB OCZ Vertex in my MacBook Pro and also a 2009 iMac, both SATA II. I got over 225MB/s read and almost 200MB/s writes.

Yes, that's about what he's showing at the high-end... Look at the xbench test.

 

[WilliamG]

Yes, that's about what he's showing at the high-end... Look at the xbench test.

Yes, but he's on a SATA III system! Very odd that those speeds are so low.

We'll wait to see what the OP has to say about his link speed in his system profile. Something definitely isn't right with those speeds, that's for sure.

 

[snipedude90]

Yes, but he's on a SATA III system! Very odd that those speeds are so low.

We'll wait to see what the OP has to say about his link speed in his system profile. Something definitely isn't right with those speeds, that's for sure.

Ok so I looked at my link speed and it's showing the same 6 gigabit negotiated link speed as my macbook air's. The only difference I see in system information is that on my MBA it says "Product: 7 series chipset" and on my imac it says that it is a 6 series. I don't know if this is in any way relevant though. I attached a screen shot of my imac's info.

I may call OWC in the morning and see if they have any reasons as to why my speeds are so low.

Not that this is too relevant but I redid the speed tests on my MBA and realized that I misrepresented the speeds I mentioned earlier. I'm getting close to 300 mb/s sustained writes and over 400 mb/s reads.

 

[WilliamG]

Let us know what you hear from OWC..

 

[shabbasuraj]

Those owc ssd speeds are fishy.

 

[snipedude90]

Update 2

Ok so I contacted OWC tech support and they sent me SpeedTools Utilities and said to use QuickBench because that is their benchmarking tool. After running the test, my results are dramatically different than what xbench and blackmagic showed. I attached a screen shot of the new benchmarks. The numbers definitely look better but I'm still perplexed as to why two other programs are showing far slower speeds.

 

[snipedude90]

Issue Resolved

After emailing with tech support, they told me that "BlackMagic and other software tools will use different testing parameters, most of the tests done through the software is testing incompressible data and other professional data sets".

So if I am interpreting this correctly, he is saying that the Xbench/BlackMagic scores are lower because they use incompressible data and QuickBench does not. This seems to make sense because the numbers I posted yesterday are seemingly consistent with the incompressible data rates listed on OWC's website. However, I don't see why the benchmarks on my Air are so high using the "professional data sets"

 

[hfg]

What OWC told you is correct regarding their Sandforce controllers (which compress write data for better performance) and testing with non-compressable data. If you try the AJA test (also free), you will see much better numbers in the disk test. Whether the higher numbers will actually improve your experience using the SSD will be determined by what you are actually using it for.

I wouldn't get too concerned about "benchmark tests" ...