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All Disk I/O Metrics Missing on EL8

gordangordan EntrantActive Member Contributor
I recently deployed a number of CentOS 8 machines and noticed that PMM 1 seems to have no disk I/O metrics for any of my EL8 machines. It is completely consistent, all of my EL7 machines have disk I/O metrics in the relevant PMM section, and none of my EL8 machines being monitored by PMM have any disk I/O metrics showing. Is this a known bug? Is there a workaround or a fix? I am using the latest version of both PMM server and client (1.17.3).

Answers

  • PeterPeter Percona CEO Percona Moderator
    Interesting. Can you share diskstats from the machines which have it working vs which do not 

    [email protected]:/proc# cat /proc/diskstats

       7       0 loop0 1 0 2 0 0 0 0 0 0 0 0

       7       1 loop1 0 0 0 0 0 0 0 0 0 0 0

       7       2 loop2 0 0 0 0 0 0 0 0 0 0 0

       7       3 loop3 0 0 0 0 0 0 0 0 0 0 0

       7       4 loop4 0 0 0 0 0 0 0 0 0 0 0

       7       5 loop5 0 0 0 0 0 0 0 0 0 0 0

       7       6 loop6 0 0 0 0 0 0 0 0 0 0 0

       7       7 loop7 0 0 0 0 0 0 0 0 0 0 0

       8       0 sda 4179883 40 135257122 1923716 6168743 2479020 154497336 2000168 0 599996 2028092

       8      16 sdb 11648 11006 186736 6000 5593 51200 454344 4880 0 1032 1408


  • gordangordan Entrant Active Member Contributor
    edited June 20
    Hi @Peter ,
    Here is an example of an EL7 x86-64 machine that works (CentOS 3.10.0-x kernel):
    # cat /proc/diskstats 
     253       0 vda 1256024 3301 62814718 1576016 26177504 36630418 1227238588 49513717 0 11628157 17548088
     252       0 zram0 0 0 0 0 0 0 0 0 0 0 0
    
    Here is an example of an EL8 x86-64 machine that doesn't (CentOS 4.18.0-x kernel):
    # cat /proc/diskstats 
       8      16 sdb 29010874 11 3206828712 15558708 49877046 0 2300829344 10392129 0 16249034 8990454 0 0 0 0
       8      17 sdb1 27338969 11 3206823352 12293716 49877046 0 2300829344 10392129 0 15748846 6486701 0 0 0 0
       8      25 sdb9 102 0 2776 24 0 0 0 0 0 19 7 0 0 0 0
       8       0 sda 28852546 13 3191231352 15388163 49589886 0 2300829344 9079365 0 16180221 7393175 0 0 0 0
       8       1 sda1 27180641 13 3191225992 12447792 49589886 0 2300829344 9079365 0 15682023 5219248 0 0 0 0
       8       9 sda9 102 0 2776 15 0 0 0 0 0 22 1 0 0 0 0
       8      32 sdc 25400284 2 6070922068 479814605 29054922 0 1446105808 57825189 0 50718113 514968864 0 0 0 0
       8      33 sdc1 25050271 2 6070916660 421643686 29054922 0 1446105808 57825189 0 50285832 456973186 0 0 0 0
       8      41 sdc9 60 0 728 220 0 0 0 0 0 31 206 0 0 0 0
       8      48 sdd 3953 0 423382 10065 753 35 153717 11474 0 4380 18524 0 0 0 0
       8      49 sdd1 59 0 712 57 0 0 0 0 0 64 21 0 0 0 0
       8      50 sdd2 3727 0 415982 9727 753 35 153717 11474 0 4206 18319 0 0 0 0
       8      64 sde 25676733 927 6076606398 476779770 28957216 0 1446105808 58024179 0 51054780 512056520 0 0 0 0
       8      65 sde1 25326720 927 6076600990 417473038 28957216 0 1446105808 58024179 0 50658048 452924794 0 0 0 0
       8      73 sde9 60 0 728 225 0 0 0 0 0 38 207 0 0 0 0
     230       0 zd0 68908 0 4569695 60369 3361792 0 147338002 1576295 0 1071117 1636664 0 0 0 0
     230       1 zd0p1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
     230       2 zd0p2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
     230      16 zd16 375968 0 19499873 181079 1502448 0 227392957 277833 0 994628 458912 0 0 0 0
     230      17 zd16p1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
     230      18 zd16p2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
     230      19 zd16p3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
     230      20 zd16p4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
    
    There seems to be an extra 4 numbers on the 4.18.0-x kernel's /proc/diskstats lines.
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