Re: Raid6 write performance

[Peter Rabbitson <rabbit+list@rabbit.us>]

Bernd Schubert wrote:
> Hello Peter,
> 
> On Monday 19 January 2009 11:37:11 Peter Rabbitson wrote:
>> Peter Rabbitson wrote:
>>> 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:
> 
> 
>> 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?