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I have an early 2009 Mac Pro(4,1). Firmware upgraded to a '10(5,1), 24GB RAM, upgraded processors to two quad core 3.46 GHz Xeons', NVIDIA GeForce GTX 760 2GB. I'm looking at the next upgrade options and an SSD comes to mind. As you probably know, the '09 and '10 have SATA II, not III. What I want to know is the performance gain from a HDD to a SSD running at SATA II, as opposed to III, worth the upgrade? Can SATA II SSDs be found at a lower price than SATA III drives, if they can be found at all?

I know I can either get a SATA III card or a PCI SSD and not have the performance hit, but that adds enough to the cost of the upgrade to not fit in the budget at this time.

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Empirically, the answer is 'Yes'.

I have a very similar machine - 4,1 -> 5,1, dual 3.46GHZ Xeons, 64GB RAM & also an older 3,1.

Both now have an SATA III 840 EVO 1TB as boot drive [best available at the time of purchase] in the first optical drive bay [leaving room for your usual 4 HDs in the regular bays. Adapter bracket a few quid/dollars/shekels from eBay.
On the 4,1 it connects directly to the cabling in the bay, the 3,1 needs a longer SATA cable down into the main body, under the cooling fans, where the two 'secret' SATA ports are.

No, they don't run at SATA III speeds, but boy do they make the entire machine more responsive. Boot time down from a couple of minutes to 15 seconds. iTunes [the slowest to launch that I know of] now launches in about 5 seconds. Finder is zippy & responsive, no more waiting for it to fill a window.

You get so used to the speed you don't notice it until you have to use a machine with a spinning HD again.

Speed test - SSD

Speed test - HD

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Yes it’s worth the upgrade. Even over a SATA II bus, the performance boost will be immediately noticeable with a SSD:

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From Is A SATA 3Gb/s Platform Still Worth Upgrading With An SSD?:

"The real key is getting an SSD into your machine. Just have a look at what happens when our 840 Pro goes up against the fastest desktop hard drive we've ever benchmarked, Western Digital's ValociRaptor. The disk didn't stand a chance in any of our synthetic or real-world tests."

I’d also recommend purchasing a SATA III SSD as they are backwards compatible. You’ll find a much wider selection at pretty much the same price point (in some cases, cheaper). Additionally, you’ll be able to use it in your next machine ;)

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  • I am not sure what "Average I/O operations" are. There is a chart, shown later in the reference you posed, comparing sequential transfers in MB/s. The results shown in this chart more closely match the technical specifications given by the manufactures of both drives. The chart demonstrates how a SATA II (3 Gb/s) interface can limit the preformance of a SSD. Sep 7 '16 at 8:15
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    @DavidAnderson, the chart is measuring the number of I/O operations that can happen per second, i.e. randomized fetches from random parts of the disk. With a HDD, the drive head needs to seek to the right track and wait for the right location of the disk to rotate under the head to access requested data. Subsequent blocks might be on different tracks and thus the head needs to keep thrashing around. This is typical of database read/write patterns. Given that SSDs have no moving part that needs to seek data, performance is instantaneous as shown. SATA II/III makes little difference here.
    – bjb
    Sep 7 '16 at 16:45
  • @bjb: SATA refers to the transfer of data to/from the drive and the host (computer). In this case SATA II is transfers at 3 Gb/s and SATA III transfers at 6 Gb/s. Your comment compares the internal workings of HDDs verses SSDs. So am I to infer that you are saying the following? Even though the latency of a SSD is far less than a HDD, both SSD and HDD have large enough latencies that a 3 Gb/s transfer speed adds little to the overall transfer times of data when access randomly. Sep 7 '16 at 18:04
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    @DavidAnderson: correct, SATA refers to the transfer of data and II vs III refers to bandwidth (3Gb vs 6Gb). Your comment questioned the chart above which doesn't refer to the SATA speed, but rather how quickly a SSD sends requested data back to the OS; HDDs have at least two mechanical activities before it can return data VS an SSD which does not. In some respects it is the more important measure for the original question since HDDs rarely saturate SATA bandwidth because they can't get to the data fast enough. SSDs CAN saturate because of this and thus why the industry is moving to M.2, etc.
    – bjb
    Sep 8 '16 at 12:16
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The performance gain with an SSD comes from the zero seek latency/time, all data is instantly accessible. That's where an SSD in consumer computers is beneficial. Massive IOPS or extreme bandwidth and NAND speeds won't help a user that much, but has a real impact in server applications and large data transfers (i.e. to and from RAM).

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