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Assuming I have a SATA III SSD drive that has a throughput of >500 MB/s. What is a reasonable estimate of the effective throughput on a SATA II controller?

I know that SATA II has 3.0 GBit/s theoretical throughput but I am looking for a value of the effective throughput.

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up vote 8 down vote accepted

I have a SATA II motherboard and a SATA III Crucial M4 SSD that can read above 400MB/s. With the AS SSD benchmark tool I get 265MB/sec read rate, indicating my maximum SATA 2 throughput.

AS SSD

I should point out that the main benefit of a SSD is not maximum transfer rate, but low latency and fast random access. You still get all those benefits on SATA 2, so it's well worth it.

To cover a real-world file transfer scenario unrestricted by drive performance, I copied a 8GB file from a SSD to another SSD with TeraCopy. It yielded an average speed of 141MB/s, indicating a total of around 280MB/s throughput.

TeraCopy

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Thanks! Accepted answer as mtone went so far as to run a benchmark for me with exactly the situation I was asking about! – ARF Feb 1 '13 at 21:16

A little bellow 300MB/s. You can read more here: http://www.tomshardware.com/reviews/sata-6gbps-performance-sata-3gbps,3110.html Also: http://en.wikipedia.org/wiki/Serial_ATA

"Second generation SATA interfaces run with a native transfer rate of 3.0 Gbit/s, and taking 8b/10b encoding into account, the maximum uncoded transfer rate is 2.4 Gbit/s (300 MB/s)."

If you put that SSD on SATA II you should expect +/- 300MB/s.

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Thanks for the link to tomshardware. It was enlightening. – ARF Feb 1 '13 at 21:14

I'd have to say it depends on the drive (rpm, cache, etc..), also the OS, are you referring to read or write, to/from what type of device, all this factors in. In the real world I have seen sata-to-sata copying of 50-60MB/s, which equates to .39-.46 GBit/s, so a little over 10% of theoretical throughput. I wasn't complaining, this was a windows machine w/ 4GB ram, and this was sustained for at least a couple of minutes.

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SATA2 can do better than that, you were probably reading and writing on the same disk (which is inherently slow). I'm sustaining 80-90MB/s copying a file between two different 7200rpm internal HDDs (that is limited by HDD write speed) and around 100-110MB/s copying from HDD to SSD. – mtone Feb 1 '13 at 18:59
    
@mtone no this was two different disks, I don't know their cache sizes and this was quite a while ago, but of course it depends on several factors, and it's still in the same ball park as mine even if it is double :-) – BigHomie Feb 1 '13 at 19:15
    
@MDMoore313 Thanks for your answer. Though you are clearly limited by the speed of your (conventional) drives. My question was referring to a situation where the speed of the drives is faster than the connection speed of the bus. Thanks anyway for trying to answer. – ARF Feb 1 '13 at 21:13

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