I don't have the source link handy, but it was an industry white paper. (I doubt you'll get it changed.) There does seem to be some interface limitation here. Running "dd if=/dev/sdX of=/dev/null bs=512k" simultaneously for various combinations of drives gives me: Port A alone : 155MByte/s Ports A & B : 105MByte/s per drive Ports A, B & C: 105MBytes/s per drive for A & B. 155MBytess's for C. Ports A, B, C & D: 105MBytes/s per drive So there's an aggregate limitation of ~1.7Gbit/s per port pair, with A&B and C&D making up the pairs. More information on the interfaces: >From lshw: description: IDE interface product: 5 Series/3400 Series Chipset 4 port SATA IDE Controller vendor: Intel Corporation physical id: 1f.2 bus info: pci@0000:00:1f.2 logical name: scsi0 logical name: scsi1 version: 05 width: 32 bits clock: 66MHz capabilities: ide pm bus_master cap_list emulated configuration: driver=ata_piix latency=0 resources: irq:20 ioport:dca0(size=8) ioport:dc90(size=4) ioport:dca8(size=8) ioport:dc94(size=4) ioport:dcc0(size=16) ioport:dcd0(size=16) >From dmesg: ata1.00: SATA link up 3.0 Gbps (SStatus 123 SControl 300) ata1.01: SATA link up 3.0 Gbps (SStatus 123 SControl 300) ata2.00: SATA link up 3.0 Gbps (SStatus 123 SControl 300) ata2.01: SATA link up 3.0 Gbps (SStatus 123 SControl 300) >From lspci: IDE interface: Intel Corporation 5 Series/3400 Series Chipset 4 port SATA IDE Controller (rev 05) (prog-if 8f [Master SecP SecO PriP PriO]) Subsystem: Dell Device 02a4 Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr+ Stepping- SERR- FastB2B- DisINTx- Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx- Latency: 0 Interrupt: pin A routed to IRQ 20 Region 0: I/O ports at dca0 [size=8] Region 1: I/O ports at dc90 [size=4] Region 2: I/O ports at dca8 [size=8] Region 3: I/O ports at dc94 [size=4] Region 4: I/O ports at dcc0 [size=16] Region 5: I/O ports at dcd0 [size=16] Capabilities: [70] Power Management version 3 Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-) Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME- Capabilities: [b0] PCI Advanced Features AFCap: TP+ FLR+ AFCtrl: FLR- AFStatus: TP- Kernel driver in use: ata_piix Kernel modules: ata_generic, pata_acpi, ata_piix -Steve Bergman -- 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
