Mark 6 performance

    Version as of 01:56, 1 Nov 2024

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    Mark6 playback performance

    playback speeds have been obtained using the EHT 2015 data. Speeds were determined by doing local reads from the vdiffuse mounted data; e.g.:

    dd if=/mark6-01_fuse/... of=dev/null bs=1M count=5000

    The measurements was done over several scans and than averaged.

    Results:

    machine speed (averaged)
    mark6-01  
    mark6-02 PV: 3120 Mbps
    mark6-03 AZ: 1275 Mbbs
    mark6-04 1224 Mbps
    mark6-05 1190 Mbps
    mark6-06  

    Test: Swaping modules

    In order to determine if the different playback speeds are due to differences in the mark6 units or tie to the data recorded on the modules two sets of modules (PV, AZ) were swapped.:

       
    mark6-02 AZ: 1272 Mbps
    mark6-03 PV: 3669 Mbps

    Playback performance seems to be tied to the data on the module. Need to repeat the playback speed measurements with recently recorded data (e.g. from the DBBC3 recordings in the lab).

    Comparison: Fuse/Gather

    Mark6 files were gathered on the fly and piped trough dd:

    ./jwagner/kvnvdiftools/gather-stdout/gather /mnt/disks/[1234]/*/data/bf114a_Lm_142-0628.vdif - | dd of=/dev/null bs=1M count=100000
    

    Results:

    90000+10000 records in
    90000+10000 records out
    99921920768 bytes (100 GB) copied, 43.7195 s, 2.3 GB/s
    

    Gathering yields much higher performance (=18 Gbps) than vdifuse (=.1.4 Gbps)

    iostat

    on mark6-01 iostat finds the following:

    Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn
    sda              12.12      1767.14         0.01  486307174       4096
    sdb              12.12      1767.17         0.01  486315780       4096
    sdc              12.12      1767.22         0.01  486328745       4096
    sdd              12.12      1767.18         0.01  486316915       4096
    sde              12.12      1767.13         0.01  486305259       4096
    sdf              12.12      1767.13         0.01  486304968       4096
    sdg              11.94      1768.72         0.01  486741075       4096
    sdh              12.12      1767.09         0.01  486292692       4096
    sdi              12.12      1767.13         0.01  486304984       4096
    sdj              11.93      1768.20         0.01  486597699       4096
    sdk              11.93      1767.90         0.01  486516615       4096
    sdl              11.95      1770.25         0.01  487163049       4096
    sdm              11.93      1767.95         0.01  486530620       4096
    sdn              11.93      1767.94         0.01  486527604       4096
    sdo              11.93      1767.94         0.01  486526314       4096
    sdp              11.93      1767.86         0.01  486506020       4096
    sdr               0.00         0.02         0.01       6119       4096
    sds              11.94      1767.81         0.01  486490497       4096
    sdt              11.94      1767.80         0.01  486487765       4096
    sdu              11.95      1769.34         0.01  486911815       4096
    sdv               0.00         0.02         0.01       6117       4096
    sdw               0.00         0.02         0.01       6121       4096
    sdx               0.00         0.02         0.01       6119       4096
    sdy               0.00         0.02         0.01       6290       4096
    sdz               0.00         0.02         0.01       6116       4096
    sdaa             12.07      1767.16         0.01  486313319       4096
    sdab              0.00         0.02         0.01       6119       4096
    sdac              0.00         0.02         0.01       6117       4096
    sdad             12.06      1767.11         0.01  486298721       4096
    sdae             12.06      1767.13         0.01  486304411       4096
    sdaf             12.06      1767.11         0.01  486300109       4096
    

    The io performance of some disks is much lower than expected. The following mount logic applies (red are slow devices):

    Module 1: g j k l m n o p

    Module2: y  aa ab ac ad ae af ag

    Module 3: r s t u v w x z

    Module 4: a b c d e f g h i

    Repeat speed measurements on Mark6 lab machines

    Mark6 machines in the correlator cluster have a redhat based OS installation. In order to check whether the differences in playback speed reported by Haystack and measured in Bonn are due to OS specific differences the speed tests were repeated on Mark6 machines running the original Debian installation.

    Results: Playback speed < 1Gbbps

    so the OS does not seem to be the reason for the slow playback speeds.

    General IO tuning

    Take a look at: http://cromwell-intl.com/linux/perfo...ing/disks.html

    IO scheduler should probably be set to noop on all mark6 machines