Jump to content
  • UNRAID ZFS HYBRID MODE READ SLOW READ MULTIPE DISK


    competent-bailout3425
    • Minor

    I have 9 disks for zfs format data disk and 2 parity disk for unraid array.When I read data from 9 data disks simultaneously through /mnt/diskx, the overall throughput is very low, only 300M/s, slightly higher than the throughput of a single disk (260M/s). At the same time, I can see that my 32-core 7d12 CPU is almost fully loaded in the background. By using the "top" command, I can see that processes like unraidd1 and unraidd2 are consuming a significant amount of CPU.

    I have confirmed that my hard disk bandwidth is sufficient to support all my disks being fully loaded for reading simultaneously. During parity check, all 11 hard disks can operate at speeds above 250M/s.

     

    some test:

    3disks

    image.thumb.png.4c4c4a27a1bb15b2461a194161ca5cba.png

    image.thumb.png.fcd064e658f5edd3c0dd5941540264fa.png

    9disks

    image.thumb.png.8a5e94bb1e727b4de3d87397e65c38b3.png

    image.thumb.png.b09ee5a4204469949b314ceae7adec83.png

     

    It is highly likely that Unraid has assigned a separate kernel thread for each disk to handle IO requests,but miuse spin locks during those thread(more disk,slow thorughput,but higher cpu usage).




    User Feedback

    Recommended Comments

    I can also reproduce the issue, reading the same zfs formatted three devices simultaneously in the array vs using separate pools:

     

    zfs.JPG

    450MB/s total

     

    image.png

    785MB/s total

     

     

     

    Link to comment


    Join the conversation

    You can post now and register later. If you have an account, sign in now to post with your account.
    Note: Your post will require moderator approval before it will be visible.

    Guest
    Add a comment...

    ×   Pasted as rich text.   Restore formatting

      Only 75 emoji are allowed.

    ×   Your link has been automatically embedded.   Display as a link instead

    ×   Your previous content has been restored.   Clear editor

    ×   You cannot paste images directly. Upload or insert images from URL.


  • Status Definitions

     

    Open = Under consideration.

     

    Solved = The issue has been resolved.

     

    Solved version = The issue has been resolved in the indicated release version.

     

    Closed = Feedback or opinion better posted on our forum for discussion. Also for reports we cannot reproduce or need more information. In this case just add a comment and we will review it again.

     

    Retest = Please retest in latest release.


    Priority Definitions

     

    Minor = Something not working correctly.

     

    Urgent = Server crash, data loss, or other showstopper.

     

    Annoyance = Doesn't affect functionality but should be fixed.

     

    Other = Announcement or other non-issue.

×
×
  • Create New...