On Thu, Jan 17, 2013 at 7:00 PM, Atchley, Scott <[email protected]> wrote:
> On Jan 17, 2013, at 9:48 AM, Gandalf Corvotempesta 
> <[email protected]> wrote:
>
>> 2013/1/17 Atchley, Scott <[email protected]>:
>>> IB DDR should get you close to 2 GB/s with IPoIB. I have gotten our IB QDR 
>>> PCI-E Gen. 2 up to 2.8 GB/s measured via netperf with lots of tuning. Since 
>>> it uses the traditional socket stack through the kernel, CPU usage will be 
>>> as high (or higher if QDR) than 10GbE.
>>
>> Which kind of tuning? Do you have a paper about this?
>
> No, I followed the Mellanox tuning guide and modified their interrupt 
> affinity scripts.

Did you tried to bind interrupts only to core to which QPI link
belongs in reality and measure difference with spread-over-all-cores
binding?

>
>> But, actually, is possible to use ceph with IPoIB in a stable way or
>> is this experimental ?
>
> IPoIB appears as a traditional Ethernet device to Linux and can be used as 
> such.

Not exactly, this summer kernel added additional driver for fully
featured L2(ib ethernet driver), before that it was quite painful to
do any possible failover using ipoib.

>
>> I don't know if i support for rsocket that is experimental/untested
>> and IPoIB is a stable workaroud or what else.
>
> IPoIB is much more used and pretty stable, while rsockets is new with limited 
> testing. That said, more people using it will help Sean improve it.
>
> Ideally, we would like support for zero-copy and reduced CPU usage (via 
> OS-bypass) and with more interconnects than just InfiniBand. :-)
>
>> And is a dual controller needed on each OSD node? Ceph is able to
>> handle OSD network failures? This is really important to know. It
>> change the whole network topology.
>
> I will let others answer this.
>
> Scott--
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