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  • 1.  iSCSI poor performance 1.5MB/s fresh install AIX7.1

    Posted Tue July 12, 2016 12:09 PM

    Originally posted by: Frenchy59


    Hi Everyone,

    I have been struggling for few days with iSCSI and thought I could get some help on the forum...

    fresh install of AIX7.1 TL4 on Power 710, The rootvg relies on 3 SAS disks in RAID 0, 32GB Memory

    The lpar

    The network seems ok, a ftp transfer between AIX & RHEL6 is 125Mb/s

    However the iSCSI transfer has really poor performance : if I do a "dd if=/dev/hdisk1 of=/dev/null" from my AIX box (on the iscsi lun), I only get 1.5Mb/s !

     

    (Please note that initially, I wanted to setup one LPAR as iscsi target, and one lpar as iscsi initiator, both using virtual ethernet adapter, and I got the same performance 1.5Mb/s between the 2 AIX lpar ... Then I decided to investigate further and to setup the whole system as a iSCSI initiator and using one of my RHEL6 iscsi target that I know works well.)

    I also tried to setup the AIX as iSCSI target and the RHEL6 as initiator, the performance gets better 8MB/s but still not acceptable, I would at least expect 30-40MB/s

     

    Any idea guys ? please solve my 1 week headache.

     

     

     

     



  • 2.  Re: iSCSI poor performance 1.5MB/s fresh install AIX7.1

    Posted Thu August 11, 2016 02:33 AM

    Originally posted by: PontiacGeronimo


    do you use dedicated iscsi adapters offloading or just an network adapter for iscsi?

     

    if network adapter then it will work so bad....



  • 3.  Re: iSCSI poor performance 1.5MB/s fresh install AIX7.1

    Posted Thu August 11, 2016 01:19 PM

    Originally posted by: Frenchy59


    Thanks for helping, I use the standard embedded NIC on the p710.
    I still think it is a limitation on AIX (a magic parameter to change?)
    To prove it, I have now narrowed down this issue, I have installed RHEL 6.5 ppc64 on the p710 and set it up as iscsi initiator, the other RHEL 6.5 x86_64 physical (not a VM) as iscsi target
    I have now really good iscsi transfer rate ! :

     
    Code: 
    [root@localhost ~]# dd if=/dev/sdb of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 9.90109 s, 108 MB/s
[root@localhost ~]# dd if=/dev/sdb of=/dev/null
^C1633537+0 records in
1633536+0 records out
836370432 bytes (836 MB) copied, 10.6675 s, 78.4 MB/s

[root@localhost ~]#


    Any idea ? any magic parameter on AIX to change that may help ?

    doing the same test on same machine with AIX gives me 15MB/s



  • 4.  Re: iSCSI poor performance 1.5MB/s fresh install AIX7.1

    Posted Thu August 11, 2016 05:01 PM

    Originally posted by: AncientAIXer


    Have you tuned the adapters?  Most AIX device attributes are set to the lowest common denominator and release time.  You may have 8 Gb/s adapters but the default attributes may be set for a 1 Gb/s adapter.  I would check the max_xfer_size and num_cmd_elems.



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