will two EVO SSDs in RAID 0 be full speed

[BirdDad]

or are they limited to SATA 3 speed, I am asking if they are limited by the controller or will 6Gbps + 6Gbps= 12Gbps? It will be on an Intel x79 chipset.
Thanks

 

[Fernando 1]

will two EVO SSDs in RAID 0 be full speed or are they limited to SATA 3 speed

The maximum speed of 2 SSDs as members of an Intel RAID0 array will not be limited by the Southbridge of your system. Only 3 or more RAID0 members will be swarthed by the SATA3 Controller.
Nevertheless you cannot expect the double speed while reading or writing small sized data.

 

[BirdDad]

why would three drives be clipped off and not two? Is it PCIe within the southbridge thats causing it? If so what is it 8x? If it was 4x it would be capped @ around 5Gbps for PCI 2.0 I'm not sure of what speed 8x 2.0 is. Just what is the limiting factor?
Thanks

 

[dave_the_nerd]

why would three drives be clipped off and not two? Is it PCIe within the southbridge thats causing it? If so what is it 8x? If it was 4x it would be capped @ around 5Gbps for PCI 2.0 I'm not sure of what speed 8x 2.0 is. Just what is the limiting factor?
Thanks

The RAID controller, probably.

There is a RAID controller that has a lot of math to do. The more drives, the more math it has to do. With two drives, it can still do more math than the drives can. With three drives, the drives can throw more math than the controller can do. So you get a bottleneck.

(I was told there would be no math.)

This is typically only noticeable with benchmarks that stress IOPS (maximum number of operations per second.) Older RAID controllers were made with hard drives in mind, hard drives can only deal with a couple hundred IOPS maximum. So a RAID controller than can handle 10,000 IOPS was great!

SSDs can do 20,000 IOPS or more individually. So throwing two of them behind a RAID controller that only does 10,000 is HORRIFYING!

A lot of motherboard (CHEAP!!!) RAID controllers are limited this way.

That said, you can still get very good sequential numbers from a RAID-0 array, even if it's bottle-necked in terms of maximum IOPS and random IO. Or you could get a dedicated hardware RAID controller. It depends on your workload and needs. If you're just benchmark whoring, well, that's fine. Get a Z9x or X99 motherboard, hook some SSDs up to the Intel SATA ports, and fire away.

Edit: the X79 is modern enough that it will be fine too for 2-4 SSDs in RAID. But you may see a performance benefit from a hardware RAID card, depending on the card.

 

[Cerb]

why would three drives be clipped off and not two?

Cost. How many cents per chip would it cost Intel to make their RAID 0 and 10, with more than 2 drives, as fast as LSI's? Keep in mind that those cents are spent regardless of whether the feature is enabled or not in a given system (IE, it will cost Intel as much going into a Celeron-based Chromebook as a desktop i7 gaming system).