On Wed, Jul 02, 2008 at 02:10:21PM -0500, Jon Nelson wrote: > On Wed, Jul 2, 2008 at 2:03 PM, Matt Garman <matthew.garman@xxxxxxxxx> wrote: > > On Wed, Jul 02, 2008 at 12:04:11PM -0500, David Lethe wrote: > >> The PCI (and PCI-X) bus is shared bandwidth, and operates at > >> lowest common denominator. Put a 33Mhz card in the PCI bus, and > >> not only does everything operate at 33Mhz, but all of the cards > >> compete. Grossly simplified, if you have a 133Mhz card and a > >> 33Mhz card in the same PCI bus, then that card will operate at > >> 16Mhz. Your motherboard's embedded Ethernet chip and disk > >> controllers are "on" the PCI bus, so even if you have a single PCI > >> controller card, and a multiple-bus motherboard, then it does make > >> a difference what slot you put the controller in. > > > > Is that true for all PCI-X implementations? What's the point, then, > > of having PCI-X (64 bit/66 MHz or greater) if you have even one PCI > > card (32 bit/33 MHz)? > > This motherboard (EPoX MF570SLI) uses PCI-E. PCI-E is quite different architecturally from PCI-X. > It has a plain old PCI video card in it: > Trident Microsystems TGUI 9660/938x/968x > and yet I appear to be able to sustain plenty of disk bandwidth to 4 drives: > (dd if=/dev/sd[b,c,d,e] of=/dev/null bs=64k) > vmstat 1 reports: > 290000 to 310000 "blocks in", hovering around 300000. > > 4x70 would be more like 280, 4x75 is 300. Clearly the system is not > bandwidth challenged. > (This is with 4500 context switches/second, BTW.) Possibly you are using an on-board disk controller, and then it most likely does not use the PCI-E bus for disk IO. best regards keld -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
