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SSD + Spindle drives on multiple controllers

Tags:
  • SSD
  • Storage
  • ASrock
  • NAS / RAID
Last response: in Storage
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April 15, 2014 6:19:13 AM

Quick question. I plan on running two RAID 1 sets, one SSD set, and one spindle set. Planning on connecting them to an ASRock Z87 Extreme4. The mobo has two SATA 6x controllers and I was planning on hooking up each set to its own controller. So, in both cases, if I have two drives attached on each controller does that mean it's only writing at 3x since it has to put both data on both drives (mirror)?

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a c 316 G Storage
April 15, 2014 7:01:41 AM

No. Each controller can run all of its ports at full speed at the same time. The rest of it I don't know whether or not it will work.
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a b G Storage
April 15, 2014 7:42:55 AM

WyomingKnott said:
No. Each controller can run all of its ports at full speed at the same time. The rest of it I don't know whether or not it will work.


I selected this as the solution since OP doesn't seem to care.

http://www.tomshardware.co.uk/answers/id-2106668/ssd-sp...
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April 15, 2014 7:47:17 AM

WyomingKnott said:
No. Each controller can run all of its ports at full speed at the same time. The rest of it I don't know whether or not it will work.


I wasn't asking if the controller will slow down. I was asking about the effective write speed. For example, if I had two drives (not RAID) on the same 6x controller and was writing to both (say from two different programs) then each would only have 3x bandwidth (no matter if it's interleaved or one after the other) over the total time.
So my assumption is that this is true for a RAID1 as well. Am I wrong there?
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a c 316 G Storage
April 15, 2014 7:54:35 AM

Yes, you are probably wrong. Could you please explain what you mean by a 6x controller? SATA III at 6 Gb/sec or an add-in controller that uses 6 PCI-E lanes?

If the former, as I've said before, a controller is supposed to be able to drive all its ports at speed. If the latter, since this is a mirror (RAID 1), it doesn't need to get the data over the PCI-E bus twice, since it's just reading it twice.

Legend has it that RAID 1 writes only slightly slower than a single drive. You do have to wait for both disks to report the commit, even if the same write was sent to both at the same time. So the slower commit always controls. Legend also has it that some RAID controllers will split the reads between two drives in RAID 1, increasing your read rates, especially in random reads. Imaging one drive seeking the next read while the other is giving you the data from your current read.

@eduello, it may have been an accidental double-post. Don't sweat it, the moderators (me) clean up doubles once they are pointed out to us.
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a b G Storage
April 15, 2014 8:00:00 AM

WyomingKnott said:
Yes, you are probably wrong. Could you please explain what you mean by a 6x controller? SATA III at 6 Gb/sec or an add-in controller that uses 6 PCI-E lanes?

If the former, as I've said before, a controller is supposed to be able to drive all its ports at speed. If the latter, since this is a mirror (RAID 1), it doesn't need to get the data over the PCI-E bus twice, since it's just reading it twice.

Legend has it that RAID 1 writes only slightly slower than a single drive. You do have to wait for both disks to report the commit, even if the same write was sent to both at the same time. So the slower commit always controls. Legend also has it that some RAID controllers will split the reads between two drives in RAID 1, increasing your read rates, especially in random reads. Imaging one drive seeking the next read while the other is giving you the data from your current read.

@eduello, it may have been an accidental double-post. Don't sweat it, the moderators (me) clean up doubles once they are pointed out to us.


That's the reason I commented, to point it out to you. Accidents happen, but those posts had multiple (over 10) questions between them. It's kind of hard to believe that would happen by accident.
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April 15, 2014 8:01:24 AM

WyomingKnott said:
Yes, you are probably wrong. Could you please explain what you mean by a 6x controller? SATA III at 6 Gb/sec or an add-in controller that uses 6 PCI-E lanes?

If the former, as I've said before, a controller is supposed to be able to drive all its ports at speed. If the latter, since this is a mirror (RAID 1), it doesn't need to get the data over the PCI-E bus twice, since it's just reading it twice.

Legend has it that RAID 1 writes only slightly slower than a single drive. You do have to wait for both disks to report the commit, even if the same write was sent to both at the same time. So the slower commit always controls. Legend also has it that some RAID controllers will split the reads between two drives in RAID 1, increasing your read rates, especially in random reads. Imaging one drive seeking the next read while the other is giving you the data from your current read.

@eduello, it may have been an accidental double-post. Don't sweat it, the moderators (me) clean up doubles once they are pointed out to us.


Wow, a bit condescending! :( 

Yes, you are right, 6 Gb/sec, not 6x! Too much multi-tasking here. Thank you for taking the time to answer my question. I was just trying to confirm that a 6 Gb/s controller can write to two drives at 6 Gb/s. For example, I want to copy a 12Gb (easy for the math) file to my RAID set. If it can move 6 Gb/s to each simultaneously then it would take 2 seconds (approx). If it had to split/interleave/divide the writes then it would take 4 seconds (approx).

Love the legend of the RAID1! :)  And yes, sorry for the double post, I hadn't even noticed that happened. The forum or my connection was being slow this morning, I probably did hit the button twice.
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a c 316 G Storage
April 15, 2014 8:04:52 AM

It's ok, even the moderators have double-posted when the forum is slow. Sorry I came off condescending, I was just trying to be comprehensive.
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April 15, 2014 8:11:07 AM

WyomingKnott said:
It's ok, even the moderators have double-posted when the forum is slow. Sorry I came off condescending, I was just trying to be comprehensive.



No worries! Again, many thanks for the answer! So this leads me to another related question. In this mobo's case, there are 6 ports on one controller and 2 ports on the other. Would there be a benefit to splitting my two RAID sets on the controllers? Or would the performance be the same if I plugged the 4 drives into the 6x controller?
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a c 316 G Storage
April 15, 2014 9:36:13 AM

It depends on the available total bandwidth between the controllers and the CPU. Motherboard designers will generally provide enough bandwidth for a controller. Considering that the 6 port controller seems to be in the chipset, it will have the necessary bandwidth.
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