3x SSD RAID0 Array Maxing out at 2x Speed instead of 3x

[spnsir]

I'm running a Windows Software RAID0 (Striped Disks).

Each disk alone reads/writes around 500 MB/s (all tested), but combined they are hitting 780 MB/s. If I stripe just two instead of three then they hit around 760 MB/s. Where is the bottle neck here? I was thinking they'd be hitting closer to 1500 MB/s, minus some overhead from the software RAID calculations.

System:
Windows 10 64-bit
3930k OC'd 4.2Ghz
Asus P9X79
32GB RAM
3x 1TB Samsung 850 EVO
256GB OCZ Vertex4 (System Drive)
Tested with two drives on MOBO 6G ports and 1 on Vantec 4-Channel Sata 6Gb/s PCIe Card and with all three drives on Vantec card (Vantec UGT-ST644R)

Testing disk speed with Blackmagic Disk Speed Test app

Why am I striping three SSDs? Video editing. They temporarily will store project files and media cache files. They are backed up daily to two other drives so potential data loss is of no concern.

 

[spnsir]

I should also add that the Vantec card is not being used for its "RAID" controller (tested also, tops out at 760 MB/s with the three drives), but is just being used to add more SATA III ports since my motherboard only has two (both already used with a system SSD and a cache SSD).

 

[Eximo]

I actually have a striped pair of vertex 4 and 800MB/s sounds familiar as a top speed, but I am using a Z87 motherboard.

Effectively you are saturating the disk controller, not much you can do about that but buy a faster card that can handle more, or replace the Vertex's with a single faster PCIe based SSD.

The Vantec controller appears to have a Marvell 88SE9230-NNA2 chip if you want to dig further.

Even on my old X58 board the Intel PCH beat the crap out of the controller's available from Marvell. I believe the much praised Sandforce controller was quickly eclipsed this time around and is found in budget SSDs.

 

[spnsir]

I actually have a striped pair of vertex 4 and 800MB/s sounds familiar as a top speed...

Do you think if I replace my mobo (and processor so it will fit the socket) with an LGA 2011-v3 that has 3+ SATA III ports the software RAID will then hit higher speeds or do I need a decent RAID card for this? Thanks for your response Eximo!

 

[geofelt]

Do not be much swayed by vendor synthetic SSD benchmarks.
They are done with apps that push the SSD to it's maximum using queue lengths of 30 or so.
Most desktop users will do one or two things at a time, so they will see queue lengths of one or two.

May I suggest you test your apps both with and without raid-0.
It takes a specially coded app that will read ahead and write behind in an overlapped manner to see the results that a synthetic benchmark gives you.

In theory, a X4 pcie device will give the best thruput.

One for read and one for write might be the optimum from a drive performance point of view.

 

[Eximo]

I actually have a striped pair of vertex 4 and 800MB/s sounds familiar as a top speed...

Do you think if I replace my mobo (and processor so it will fit the socket) with an LGA 2011-v3 that has 3+ SATA III ports the software RAID will then hit higher speeds or do I need a decent RAID card for this? Thanks for your response Eximo!

Not enough to matter.

I wouldn't rely on software raid for that anyway, the onboard raid controllers are more then capable of handling it themselves without relying on Windows.

Certainly the wiser investment is a more powerful PCIe RAID card, then you are not platform bound. But I think the best investment might be one of those PCIe -> M.2 adapters so you can change out the drives as your needs changes.