Use of 2.5″ Laptop Drives in a Server

Given equivalent sizes, the SSD's will give you vastly more I/O operation performance than the SATAs will.

Both are fast enough to saturate the SATA connection given the right I/O access patterns, though the SSD's will deliver it more often.

As with most performance comparisons, it depends on what you're doing with them. At sizes like these I suspect you're more concerned with throughput than bulk storage. The SSD config will blow the SAS drives out of the water for the lots-of-random-tiny-accesses usage pattern, and you're going to be more constrained on your RAID1 controller (if hardware) or your SATA links.

The big caveat is one ErikA pointed to. The cheapest SSD drives you can get won't do much better than the SAS drives and will most certainly die a lot faster. The more advanced drives will both last longer and withstand more pounding.

I believe that Womble's comment to Peter Schofield is the best observation here...these aren't true SAS disks.

No doubt you're being sold "nearline SAS", which is where they take a SATA disk and put a SAS interface on it. The drive mechanics are identical to the SATA version; only the interconnect has changed.

When you plug a nearline SAS drive into a SAS controller, it will be faster than the equivalent SATA drive because the protocols are different, and it takes a certain amount of time to convert between the SATA protocol and the SAS protocol. Wikipedia says that there can be a 30% increase in speed, but I've never delved into the protocols themselves, so I couldn't tell you.

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As an aside, I really don't know what kind of faith I'd put into those numbers. Storage Review does a pretty decent job, I think, but I can't figure out why they didn't get another drive to test when the disk started performing like this:

_{(source: storagereview.com)}

That's a drive that should be physically identical and in terms of interface, should be performing much more in-line with the others. The fact that it shows a discrepancy like this indicates (to me, anyway), that there was something wrong with the device.

They do say that it checks out with Seagate's test suite, but I wouldn't put stock in the results until they're checked against another drive of the same model. Those results are just too weird.

Edit

Since it was brought to my attention that I didn't actually answer the question, my guess is that the SAS drive will give you better performance because of the reasons I listed above. That is what I would go with, unless research bears out the odd results that Storage Review got.