I got a 128Gb SM951 and Lycom DT-120 for £83. Reads at 1.5Gbps (capped by PCIe 2.0), writes round 750Mbps, with impressive IOPS.
Say you got 4x 120Gb Samsung 750 Evos. Best price I could find is on Amazon for £47. So £188. Plus, you'd need something to attach them to, as they don't attach to the sleds normally. You could just get a simple 2.5" to 3.5" adapter, such as a dock for a Raptor drive, they're normally around £9, so 4x is £36. £224. Or you could be cheap and use gaffa tape, who knows 😉 But you're limited by the SATA controller to a max of around 660Mbps red/write, and could suffer disk failure of any one of 4 units, taking out your entire array if using RAID0.
So, even saying you're cheap, and attach the 2.5" drives to the sleds with gaffa, you're still spending £188.
2x 128Gb SM951s in RAID0 scale really well, and aren't capped by the SATA controller, so you'd get roughly 3Gbps read, 1.5Gbps write, decent IOPS, for £166.
I guess it depends what you're after, more space or more speed?
I wanted a fast OS and Apps, but don't need SSDs for media. 1 SM951 for the OS is fine, all my media is stored on 4x 2Tb 7,200rpm disks using with OpenZFS. Runs really well, configured in RAIDZ (basically RAID5) so can suffer one failure without any loss of data. I then replicate this to a FreeNAS box running RAIDZ2 (RAID6).
No, OP was talking about plug that into the native port. There is no adaptor require. Just plug a SSD in, leave it at there is fine. I myself has SSD like that. No extra cost, the SSD is so light, and the SATA port is actually strong enough it hold the SSD at there for years. If worry, a tape can help for virtually zero cost.
We only need SATA 2 speed SSD, so, no need to go for any expensive model. I got my 120G SSD for less than $30, a brand call DGM (link in my signature). Via a native SATA 2 port. I can't feel any different than my 1T 840 evo. Even running benchmark, they both capped at 250MB/s anyway.
And you are comparing a total 480G SSD storage option to another 256G option with roughly the same cost. It's what I want to say, for the same size, SATA option should be cheaper. Unless go for the SATA 3 card. In this case, I will go for PCIe SSD (unless boot to Windows is required).
However, I agree that the speed should max at about 660MB/s even RAID all 4 together, and ~4x failure rate.
So, it really depends on if the user needs speed / size. However, if only need high IOPS, but not require high sequential speed. Nothing can beat the SATA 2 port option in term of setup cost.
Also, occupy a SATA port is not necessary bad, if that helps to free up one PCIe slot. Of cost there are PCIe card can handle 4 PCIe SSD in full speed, but that's extremely expensive, so won't help to reduce cost.
Anyway, my last post only want to point out that it's quite impossible to get a PCIe SSD storage option that can be cheaper than native SATA 2 port option (for the same size). I am not saying that PCIe SSD is bad, or not worth etc. If I have empty slot, I will also get a PCIe SSD, but at this moment, I even didn't install my SATA 3 card, because the 2nd GPU helps me more most of the time. And there is virtually no difference on boot time, loading time, etc by running the SSD via SATA 2 port and SATA 3 card. The random small files read write speed simply cannot saturate the SATA 2 bandwidth.
