Re: Performance, and how much wiggle room there is with tunables

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Hi Mark,

It will be interesting to know:

The impact of replication. I guess it will decrease by a higher factor than the replica count.

I assume you mean the 30K IOPS per OSD is what the client sees, if so the OSD raw disk itself will be doing more IOPS, is this correct and if so what is the factor ( the less the better efficiency).

Are you running 1 OSD per physical drive or multiple..any recommendations ?

Cheers /Maged

On 2017-11-10 18:51, Mark Nelson wrote:

FWIW, on very fast drives you can achieve at least 1.4GB/s and 30K+ write IOPS per OSD (before replication).  It's quite possible to do better but those are recent numbers on a mostly default bluestore configuration that I'm fairly confident to share.  It takes a lot of CPU, but it's possible.

Mark

On 11/10/2017 10:35 AM, Robert Stanford wrote:

 Thank you for that excellent observation.  Are there any rumors / has
anyone had experience with faster clusters, on faster networks?  I
wonder how Ceph can get ("it depends"), of course, but I wonder about
numbers people have seen.

On Fri, Nov 10, 2017 at 10:31 AM, Denes Dolhay <denke@xxxxxxxxxxxx
<mailto:denke@xxxxxxxxxxxx>> wrote:

    So you are using a 40 / 100 gbit connection all the way to your client?

    John's question is valid because 10 gbit = 1.25GB/s ... subtract
    some ethernet, ip, tcp and protocol overhead take into account some
    additional network factors and you are about there...


    Denes


    On 11/10/2017 05:10 PM, Robert Stanford wrote:

     The bandwidth of the network is much higher than that.  The
    bandwidth I mentioned came from "rados bench" output, under the
    "Bandwidth (MB/sec)" row.  I see from comparing mine to others
    online that mine is pretty good (relatively).  But I'd like to get
    much more than that.

    Does "rados bench" show a near maximum of what a cluster can do?
    Or is it possible that I can tune it to get more bandwidth?
    |
    |

    On Fri, Nov 10, 2017 at 3:43 AM, John Spray <jspray@xxxxxxxxxx
    <mailto:jspray@xxxxxxxxxx>> wrote:

        On Fri, Nov 10, 2017 at 4:29 AM, Robert Stanford
        <rstanford8896@xxxxxxxxx <mailto:rstanford8896@xxxxxxxxx>> wrote:
        >
        >  In my cluster, rados bench shows about 1GB/s bandwidth.
        I've done some
        > tuning:
        >
        > [osd]
        > osd op threads = 8
        > osd disk threads = 4
        > osd recovery max active = 7
        >
        >
        > I was hoping to get much better bandwidth.  My network can
        handle it, and my
        > disks are pretty fast as well.  Are there any major tunables
        I can play with
        > to increase what will be reported by "rados bench"?  Am I
        pretty much stuck
        > around the bandwidth it reported?

        Are you sure your 1GB/s isn't just the NIC bandwidth limit of the
        client you're running rados bench from?

        John

        >
        >  Thank you
        >
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