3WARE 9550 PCI-X 133mHz in PCI-X 66mHz slot loss of performance?

monsterjta

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I have a H8DAE motherboard with 2x 133mHz slots and 2x 66mHz slots. I plan to fill this server with 16 SATA drives. I can get a better deal on 4x 9550SXU-4LP cards than 1x 9550SXU-16ML card. But then I'd have to use the 66mHz slots.

Will using the 66mHz slots degrade the performance of these 133mHz controller cards?
 

MattP725

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well I will tell you that standard PCI can only handle Sata 1.5gbs due to bandwith limitations. Based upon that and depending on your raid setup I would assume it would slow everything down to approx 1.5gbs (depending on your setup of the 16 drives which wasn't really specified).
 
No, not really. However, this really depends on how you are using the arrays plugged into those slots, meaning that if there is heavy I/O from multiple users pulling on one specific array, then there may be some lag. But again, chances are you will not see any significant performance degredation.
 

monsterjta

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I ended up getting the high capacity card with enough ports, so the question is mute (for me at this point, anyway). But, the main goal is high performance for this system. I'll be setting up a RAID 10 for the first set of 8 disks, which will host several VM disk via iSCSI, as well as a couple high transaction (OLTP) SQL databases in a clustered configuration. The remaining 8 disks will be RAID 5, with high capacity 7200RPM drives, which will be used purely as a mass storage and backup target (high performance not required). So, that's the setup. Any other input would be appreciated, if not only for others reading this post.

Thanks everyone.
 

monsterjta

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Thanks for the input, MattP725. Do you have any references you can point me to? I'd like to read up on this 1.5gbps bandwidth limitation for 66mHz PCI slots.
 

1309

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on a PCI-X bus the bus speed will be limited to the clock frequency of the slowest card, an inherent limitation of PCI's shared bus topology. For example, when a PCI 2.3, 66-MHz peripheral is installed into a PCI-X bus capable of 133 MHz, the entire bus backplane will be limited to 66 MHz. To get around this limitation and the voltage compatibility issue, many motherboards have multiple PCI/PCI-X buses, with one bus intended for use with high-speed PCI-X peripherals, and the other bus intended for general-purpose peripherals.