RAID Question

[OrbitzXT]

I have this motherboard, and currently have 2 Crucial M4 SSD's setup in RAID 0 on the two SATA III ports on this motherboard. A friend of mine is offering me a third SSD at no cost, the same model/bios revision.

My question basically comes down to, do I have any use for this? Since my motherboard only has two SATA III ports and the rest are SATA II, can I even make use of a third SSD? At the moment I get about 950 MB/s read speed from the two drives. What would you guys do in this situation?

 

[Disparia]

I would go for it! If nothing else, for more space. But better benches doesn't hurt either.

 

[OrbitzXT]

How would I actually use it though? Can you create a RAID 0 array with 2 SSDs on the SATA III ports and the third on a SATA II port? Or would I have to move them all over to SATA II? If so, would 3 drives on SATA II outperform 2 drives on SATA III?

 

[lilhasselhoffer]

?

Why not?

You can't use the thing in an additional RAID (different controllers means RAID isn't possible), and it would definitely saturate the SATA II interface.

At the same time, a secondary SSD for games and programs (to minimize read/writes to the main RAID) is always a good idea.


Edit:
Ideal speed calculations:
SATA III = SATA IIx2, so RAID 0 would be SATA IIx4 speeds
SATA IIx3 is the ideal theoretical speed of a three disk SSD RAID array
While actual performance will be less than ideal, the math behind your choice should be simple.

Edit:
My experience with a SB-e board has lead me to believe running three drives in RAID, with only one being on a SATA II port, is not an ideal situation. The performance of all three seems to take a hit, as though the SATA III and SATA II communication has some substantial overhead. No numbers, which is hard to say, but personal experience tells me this is a less than ideal situation.

 

[Disparia]

Info at Intel's site says that you should be able to have one on a 3Gb port, with the others on the 6Gb ports.

However, awhile back I said that I'd never buy SB - and so far I've stuck with it! Does leave me with a lack of hands-on experience regarding the RAID options though. Can wait for some clarification from user with PCH RAID experience.

 

[newtekie1]

Either way, you are going to be limitted by the read speed of the SATA 3Gbps port, which is going to max out at about 300MB/s. So because of the way RAID works you are going to basically get 3x 300MB/s even with 2 drives in the SATA 6Gbps ports which would be 900MB/s, best case. The reason for this is because when ever you do a Read/Write to the array, the array has to wait on the slowest member. So you would be loosing a little on the read speed, but gaining the storage space. So if the storage is needed then go for it, otherwise I say stick with what you got.

 

[OrbitzXT]

Either way, you are going to be limitted by the read speed of the SATA 3Gbps port, which is going to max out at about 300MB/s. So because of the way RAID works you are going to basically get 3x 300MB/s even with 2 drives in the SATA 6Gbps ports which would be 900MB/s, best case. The reason for this is because when ever you do a Read/Write to the array, the array has to wait on the slowest member. So you would be loosing a little on the read speed, but gaining the storage space. So if the storage is needed then go for it, otherwise I say stick with what you got.

Are there motherboards with more than 2 SATA III ports? If so, what's the highest speeds you can reach before you hit some sort of limitation?

 

[newtekie1]

Are there motherboards with more than 2 SATA III ports? If so, what's the highest speeds you can reach before you hit some sort of limitation?

Yes, but any ports beyond the first 2 will be on a 3rd party controller. So RAID with all the ports is impossible. I think there are some with 4 extra SATA III ports, for a total of 6, allowing for RAID arrays with 4 drives.

As for the highest speeds, well it is complicated. The controllers are connected to the system using standard PCI-E. So you start to hit the limit of the PCI-E bus eventually. If you really wanted to, you could just add a 3rd party card to your board yourself, but it would need to be a PCI-E x4 card. So the card would have to do in your second PCI-E x16 slot, forcing both slots to run at x8, which would limit the bandwidth to your primary card which I'm sure you don't want to do.