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Gabriel-M

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Does RAID 6+0 (60) increase performance with more drives?

Hi Experts,

I would like to know if I were to add more drives to a RAID 6+0 array if the performance would increase as well as capacity? Or would the performance remain the same?

I see that RAID 6+0 has 4 disks per set, and 2 sets, making 8.

How would the controller set it up if I had a 24 disk array? 6 sets of 4 per set? Or 2 sets of 12 per set?

Thank you very much for any help!
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Rojosho
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"Performance" will increase the most on sequential reads.  If doing sequential writes, then it will usually increase.  If performing random I/O, then, in general, you will be better off creating additional arrays.  Remember that optimizing for IOPs and throughput are nearly mutually exclusive.   Your mileage may vary, as I/O characteristics vary considerably depending on the firmware and architecture of the controller, as well as the disk drives.  

For example, SAS drives have separate read and write channels, so write and read operations do not compete against each other for bandwidth.  The same can not be said for SCSI, and most SATA implementations.

Personally, I can't think of any real-world situation where 2x12 drives will be a good thing other than video streaming or data acquisition, and even then, it depends on the number of streams and disk technology.
"... if I were to add more drives to a RAID 6+0 array if the performance would increase ..."  ==>   Yes.    Since you're adding more drives to the stripe, you'll get higher sustained transfer speeds.    However, this won't help with IOPs (as noted above), since the access characteristics won't change (you still need to seek to the data).    Bottom line:  Transfers will be quicker, but the impact on IOPs will be small (You'll see a slight gain).

"... How would the controller set it up if I had a 24 disk array? 6 sets of 4 per set? Or 2 sets of 12 per set?  "   ==>  The controller doesn't decide that -- YOU do.    As noted above, if your goal is to maximize IOPs, you're better off with multiple arrays;  if you want to maximize data transfer speeds, then a large number of drives will be best (i.e. 2 x 12 would have a very faster transfer rate).
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Gabriel-M

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Thank you for the fast replies. Before I close this I want to make sure I understand this perfectly.

IOPs in this instance isn't as important as transfer speed (and of course security of the data) to me.

2 x 12 would be "faster" than 6 x 4 in theory?

Let me explain a little more.

             |-------------raid-0------------|
(raid-6)[12 disks]               (raid-6)[12 disks]

                                or

            |--------------------|--------------------|-------raid-0------|--------------------|--------------------|
(raid-6)[4 disks]  (raid-6)[4 disks]  (raid-6)[4 disks]  (raid-6)[4 disks]  (raid-6)[4 disks]  (raid-6)[4 disks]

I am assuming that 6 arrays of 4 disks each is better for data transfer speed?

Thank you for the help! I really appreciate it.
Also, which one my my examples is able to have a larger usable drive size?
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Alright, thank you (great answer garycase)! (dlethe: That would use another question thread to answer, and I will keep bus saturation in mind ;-) ). I think that just about answers it for me. I really appreciate all input. I'll close this question now.
Thanks everyone!
Bus saturation (as mentioned above) can indeed be an issue -- but I'm assuming that if you have a controller that supports 24 drives it's on at least a PCIe x4 bus, so that shouldn't be an issue.    The AVSForum has an example of a 24-drive RAID-6 with an Areca controller that achieves a consistent 800MB/s with burst speeds over 1GB.    You should get fairly close to this with a 2 x 12 array.

Here's the HDTach display from the AVS thread:


hdtachareca256mbvc3.jpg
That's incredible. And yes, it will be on a PCIe card for sure, and at least 4x (if not 8 or 16). I haven't chosen the hardware yet. Still in the planning stages. Hence this question. Thank you SO MUCH everyone!!! <3
Gabriel-M,

You are welcome and thank you.