[lustre-discuss] Lustre over 10 Gb Ethernet with and without RDMA

[INKozin]

I know that QDR IB gives the best bang for buck currently and that's what
we have now. However due to various reasons we are looking at alternatives
hence the question. Thank you very much for your information, Ben.

On 19 June 2015 at 16:24, Ben Evans <bevans at cray.com> wrote:

>  It’s faster in that you eliminate all the TCP overhead and latency.
> (something on the order of 20% improvement in speed, IIRC, it’s been
> several years)
>
>
>
> Balancing your network performance with what your disks can provide is a
> whole other level of system design and implementation.  You can stack
> enough disks or SSDs behind a server so that the network is your
> bottleneck, you can stack up enough network to few enough disks so that the
> drives are your bottleneck.  You can stack up enough of both so that the
> PCIE bus is your bottleneck.
>
>
>
> Take the time and compare costs/performance to Infiniband, since most
> systems have a dedicated client/server network, you might as well go as
> fast as you can.
>
>
>
> -Ben Evans
>
>
>
> *From:* igko50 at gmail.com [mailto:igko50 at gmail.com] *On Behalf Of *INKozin
> *Sent:* Friday, June 19, 2015 11:10 AM
> *To:* Ben Evans
> *Cc:* lustre-discuss at lists.lustre.org
> *Subject:* Re: [lustre-discuss] Lustre over 10 Gb Ethernet with and
> without RDMA
>
>
>
> Ben, is it possible to quantify "faster"?
>
> Understandably, for a single client on an empty cluster it may feel
> "faster" but on a busy cluster with many reads and writes in flight I'd
> have thought the limiting factor is the back end's throughput rather than
> the network, no? As long as the bandwidth to a client is somewhat higher
> than the average i/o bandwidth (back end's throughput divided by the number
> of clients) the client should be content.
>
>
>
> On 19 June 2015 at 14:46, Ben Evans <bevans at cray.com> wrote:
>
> It is faster, but I don’t know what price/performance tradeoff is, as I
> only used it as an engineer.
>
>
>
> As an alternative, take a look at RoCE, it does much the same thing but
> uses normal (?) hardware.  It’s still pretty new, though, so you might have
> some speedbumps.
>
>
>
> -Ben Evans
>
>
>
> *From:* lustre-discuss [mailto:lustre-discuss-bounces at lists.lustre.org] *On
> Behalf Of *INKozin
> *Sent:* Friday, June 19, 2015 5:43 AM
> *To:* lustre-discuss at lists.lustre.org
> *Subject:* [lustre-discuss] Lustre over 10 Gb Ethernet with and without
> RDMA
>
>
>
> My question is about performance advantages of Lustre RDMA over 10 Gb
> Ethernet. When using 10 Gb Ethernet to build Lustre, is it worth paying the
> premium for iWARP? I understand that iWARP essentially reduces latency but
> less sure of its specific implications for storage. Would it improve
> performance on small files? Any pointers to representative benchmarks will
> be very appreciated.
>
>
>
> Celsio has released a white paper in which they compare Lustre RDMA over
> 40 Gb Ethernet and FDR IB
>
>
> http://www.chelsio.com/wp-content/uploads/resources/Lustre-Over-iWARP-vs-IB-FDR.pdf
>
> where they claim comparable performance of both.
>
> How much worse the throughput on small block sizes would be without iWARP?
>
>
>
> Thank you
>
> Igor
>
>
>
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