Re: Raid6 write performance

Bernd Schubert wrote:

Hello Peter,

On Monday 19 January 2009 11:37:11 Peter Rabbitson wrote:

quoted

Peter Rabbitson wrote:

quoted

Hi,

I am experimenting with raid6 on 4 drives on 2.6.27.11. The problem I am
having is that no matter what chunk size I use, the write benchmark
always comes out at single drive speed, although I should be seeing
double drive speed (read speed is at near 4x as expected).

Please disregard this, I appear to be having some sort of weird hardware
congestion. Can someone explain what could be going on?

I don't know what it is going on, but:

quoted

Combined read speed - limited by the width of a 32bit 66mhz PCI (dev
02:04.0 below)

No! You you do have PCI-X, so 64bit with 66MHz. Maybe you are even luckily and 
it is as 133MHz, depends on how many other devices are connected to this bus. 
lspci will always say it is running at 66MHz, though, it also might run at 
100 or 133 MHz,

And on the same bus (the last lspci) I have:

02:04.0 Ethernet controller: Intel Corporation 82541PI Gigabit Ethernet
Controller (rev 05)
	Subsystem: Intel Corporation PRO/1000 GT Desktop Adapter
	Flags: bus master, 66MHz, medium devsel, latency 64, IRQ 26
	Memory at fc5a0000 (32-bit, non-prefetchable) [size=128K]
	Memory at fc580000 (32-bit, non-prefetchable) [size=128K]
	I/O ports at b000 [size=64]
	Expansion ROM at fc460000 [disabled] [size=128K]
	Capabilities: [dc] Power Management version 2
	Capabilities: [e4] PCI-X non-bridge device
	Kernel driver in use: e1000

which afaik brings everything to 32bits no?