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Onboard vs PCI-E 1x RAID Controller

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September 1, 2009 12:21:17 AM

Is there any speed difference between Onboard and PCI-E 1x RAID Controllers? I got a PCI-E 1x RAID controller to do RAID 0, but I didn't realize my mobo supported RAID. Wouldn't PCI-E become a bottleneck since it has a cap of 2.5 Gb/s while the SATA II HDs have a cap of 3 Gb/s for each drive? And is the mobo RAID controller software or hardware based?

Don't tell me to not use RAID 0 please.
September 1, 2009 2:03:01 AM

Nevermind. It seems my mobo only supports RAID 1.
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September 1, 2009 3:28:20 PM

Maybe not for you, OP, but for others. Although SATA II has a max burst speed of 3Gb/s, you'll never see that on any sustained basis. Likewise, you'll never see 2.5 Gb/s sustained through a PCIe x1 bus, either. So the PCIe x1-mounted controller is not going to create a bottleneck. Done properly, it can actually speed things up a little, and provide some protection against future failures.

ALL RAID controllers "built in" on the mobo's Southbridge use "software RAID". That is, it has all the code required in the chip, but most of the actual processing is done by the CPU. If you install a separate RAID controller card, especially the cheaper ones, you may get the same result - the card has the HDD controllers and code, but no dedicated processor on board, so it assigns all processing to the main CPU. But better-quality cards have their own processor on board and do all the work themselves, freeing up CPU time. That's how you MAY get a small performance boost from using a separate card.

One thing that worries users of RAID arrays is how to recover from equipment failure. This has it roots in the fact that there is no universal standard for the low-level details of how RAID disks are written and managed. The result is that RAID disks written by one controller system probably will NOT be usable by a different manufacturer's controller. The best protection for the entire RAID system, like any other data storage system, is an excellent data backup system with frequent redundant backups stored offsite, etc. But to protect against failure of the controller itself, one option is to use a separate dedicated controller card (rather than built-in on the mobo) from a major manufacturer, in the faith that the card can always be replaced by a new one from the same manufacturer that is guaranteed to work with drives already written by an earlier card.
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December 6, 2010 9:49:25 AM

Hi paperdoc that replay was really nice!

I have an issue.

Do you think that using 2 (cheap) raid controllers with one HDD connect on each will improve my performance running RAID 0?

And.. Does that work? I mean... could 2 raid controllers pci-e 1 run Raid 0?

tks a lot

Rodrigo

Currently I'm using one RAID controller and 2 HDDs connect on it.
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October 13, 2011 5:57:48 AM

cabecinhas_br said:
Hi paperdoc that replay was really nice!

I have an issue.

Do you think that using 2 (cheap) raid controllers with one HDD connect on each will improve my performance running RAID 0?

And.. Does that work? I mean... could 2 raid controllers pci-e 1 run Raid 0?

tks a lot

Rodrigo

Currently I'm using one RAID controller and 2 HDDs connect on it.


It should as two connectors on one card will share one PHY I.E 1/2 the bandwidth per HD ; however using 2 cards should mean that you now have one HD on a two channel PHY ensuring maximum bandwidth and being that they are on separate PCIe slots there should be no contention for bandwidth.
A lot of the on motherboard SATA connectors where there are two ports are unfortunately sharing bandwidth on their PHYs and unfortunately this really slows down the raid.
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October 13, 2011 12:06:41 PM

cabecinhas_br said:

Do you think that using 2 (cheap) raid controllers with one HDD connect on each will improve my performance running RAID 0?

And.. Does that work? I mean... could 2 raid controllers pci-e 1 run Raid 0?
Currently I'm using one RAID controller and 2 HDDs connect on it.


This won't work. All the drives in RAID must be on the same controller. Seperate controllers can't communicate with each other.
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October 13, 2011 12:18:54 PM

Hawkeye22 said:
This won't work. All the drives in RAID must be on the same controller. Seperate controllers can't communicate with each other.


I don't know that that statement is 100% correct, it would depend I believe on the two separate cards being from the same manufacturer, admittedly when I did this previously I was using to generic cards running SATA 1 on CMD chipset raid cards but I had set up raid 0 across the two controllers because the BIOS allowed it.
I have not attempted this however with two PCIe controllers but wouldn't expect it to be two much different.

What I do know it that if you have one card with one controller chip on it then ( and I haven't found an exception to this rule ) the bandwidth it split between the two physical SATA connectors on the card. I.E 1 HD only = full speed on that card 2 HD's on the one card = 1/2 the bandwidth each.

I did this on a Asus Striker II Extreme and yes I am aware that I am now talking about a motherboard rather than a card but when two hard drives were connected one set of connectors I.E 2.0 and 2.1 it ran at 1/2 speed but when you ran them on 1.0 and 2.0 it ran at full speed.

So correct me please if I am wrong but I believe a lot of it comes down to the cards on board bios.

Cheers.
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