disk %util reaches 100% constantly when avgrq-sz is small

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On my system with 4.9.86 kernel I have noticed weird behaviour with my disk (HDD with 5400 rpm), the %util goes 100% for quite some time constantly (for 5 minutes or so), I do see the avrg-rq size is 8K when this happens. avgqu-sz and await is also very high, causing many processes going into D state (including jdb2 thread) . I have also noticed KBDirty going high this time (658 MB in this case which is usually in few KBs otherwise), Am I hitting disk saturation?



SAR Memory Usage:======================================
Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)
11:29:20    kbmemfree kbmemused  %memused kbbuffers  kbcached  kbcommit   %commit  kbactive   kbinact   kbdirty
11:29:21     80270488  52009236     39.32    354368  17373312  15789156      7.92  10257860  15388656    658488
Average:     80270488  52009236     39.32    354368  17373312  15789156      7.92  10257860  15388656    658488

SAR IO Usage:======================================
Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)

11:29:22          tps      rtps      wtps   bread/s   bwrtn/s
11:29:23       351.00      0.00    351.00      0.00   2808.00
Average:       351.00      0.00    351.00      0.00   2808.00

SAR Device IO activity:======================================
Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)

11:29:23          DEV       tps  rd_sec/s  wr_sec/s  avgrq-sz  avgqu-sz     await     svctm     %util
11:29:24        loop5      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
11:29:24          sda    285.00      0.00   2280.00      8.00    143.51    510.94      3.51    100.00
11:29:24        vault      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
Average:          DEV       tps  rd_sec/s  wr_sec/s  avgrq-sz  avgqu-sz     await     svctm     %util

Average:        loop5      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
Average:          sda    285.00      0.00   2280.00      8.00    143.51    510.94      3.51    100.00
Average:        vault      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00

SAR Queue and Load avg:======================================
Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)

11:29:25      runq-sz  plist-sz   ldavg-1   ldavg-5  ldavg-15   blocked
11:29:26            0      1043      3.39      2.30      2.15         2
Average:            0      1043      3.39      2.30      2.15         2


the file system mounted as ext3 with ext4 driver, data=ordered,barrier=0 setting with journaling enabled.



Raid configuration:




  Model:SAS2008 Firmware Version: 9.00.00.00 RAID Level:RAID1
 











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    2















    On my system with 4.9.86 kernel I have noticed weird behaviour with my disk (HDD with 5400 rpm), the %util goes 100% for quite some time constantly (for 5 minutes or so), I do see the avrg-rq size is 8K when this happens. avgqu-sz and await is also very high, causing many processes going into D state (including jdb2 thread) . I have also noticed KBDirty going high this time (658 MB in this case which is usually in few KBs otherwise), Am I hitting disk saturation?



    SAR Memory Usage:======================================
    Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)
    11:29:20    kbmemfree kbmemused  %memused kbbuffers  kbcached  kbcommit   %commit  kbactive   kbinact   kbdirty
    11:29:21     80270488  52009236     39.32    354368  17373312  15789156      7.92  10257860  15388656    658488
    Average:     80270488  52009236     39.32    354368  17373312  15789156      7.92  10257860  15388656    658488

    SAR IO Usage:======================================
    Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)

    11:29:22          tps      rtps      wtps   bread/s   bwrtn/s
    11:29:23       351.00      0.00    351.00      0.00   2808.00
    Average:       351.00      0.00    351.00      0.00   2808.00

    SAR Device IO activity:======================================
    Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)

    11:29:23          DEV       tps  rd_sec/s  wr_sec/s  avgrq-sz  avgqu-sz     await     svctm     %util
    11:29:24        loop5      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
    11:29:24          sda    285.00      0.00   2280.00      8.00    143.51    510.94      3.51    100.00
    11:29:24        vault      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
    Average:          DEV       tps  rd_sec/s  wr_sec/s  avgrq-sz  avgqu-sz     await     svctm     %util

    Average:        loop5      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
    Average:          sda    285.00      0.00   2280.00      8.00    143.51    510.94      3.51    100.00
    Average:        vault      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00

    SAR Queue and Load avg:======================================
    Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)

    11:29:25      runq-sz  plist-sz   ldavg-1   ldavg-5  ldavg-15   blocked
    11:29:26            0      1043      3.39      2.30      2.15         2
    Average:            0      1043      3.39      2.30      2.15         2


    the file system mounted as ext3 with ext4 driver, data=ordered,barrier=0 setting with journaling enabled.



    Raid configuration:




      Model:SAS2008 Firmware Version: 9.00.00.00 RAID Level:RAID1
     











    share|improve this question


























      2












      2








      2








      On my system with 4.9.86 kernel I have noticed weird behaviour with my disk (HDD with 5400 rpm), the %util goes 100% for quite some time constantly (for 5 minutes or so), I do see the avrg-rq size is 8K when this happens. avgqu-sz and await is also very high, causing many processes going into D state (including jdb2 thread) . I have also noticed KBDirty going high this time (658 MB in this case which is usually in few KBs otherwise), Am I hitting disk saturation?



      SAR Memory Usage:======================================
      Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)
      11:29:20    kbmemfree kbmemused  %memused kbbuffers  kbcached  kbcommit   %commit  kbactive   kbinact   kbdirty
      11:29:21     80270488  52009236     39.32    354368  17373312  15789156      7.92  10257860  15388656    658488
      Average:     80270488  52009236     39.32    354368  17373312  15789156      7.92  10257860  15388656    658488

      SAR IO Usage:======================================
      Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)

      11:29:22          tps      rtps      wtps   bread/s   bwrtn/s
      11:29:23       351.00      0.00    351.00      0.00   2808.00
      Average:       351.00      0.00    351.00      0.00   2808.00

      SAR Device IO activity:======================================
      Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)

      11:29:23          DEV       tps  rd_sec/s  wr_sec/s  avgrq-sz  avgqu-sz     await     svctm     %util
      11:29:24        loop5      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
      11:29:24          sda    285.00      0.00   2280.00      8.00    143.51    510.94      3.51    100.00
      11:29:24        vault      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
      Average:          DEV       tps  rd_sec/s  wr_sec/s  avgrq-sz  avgqu-sz     await     svctm     %util

      Average:        loop5      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
      Average:          sda    285.00      0.00   2280.00      8.00    143.51    510.94      3.51    100.00
      Average:        vault      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00

      SAR Queue and Load avg:======================================
      Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)

      11:29:25      runq-sz  plist-sz   ldavg-1   ldavg-5  ldavg-15   blocked
      11:29:26            0      1043      3.39      2.30      2.15         2
      Average:            0      1043      3.39      2.30      2.15         2


      the file system mounted as ext3 with ext4 driver, data=ordered,barrier=0 setting with journaling enabled.



      Raid configuration:




        Model:SAS2008 Firmware Version: 9.00.00.00 RAID Level:RAID1
       











      share|improve this question
















      On my system with 4.9.86 kernel I have noticed weird behaviour with my disk (HDD with 5400 rpm), the %util goes 100% for quite some time constantly (for 5 minutes or so), I do see the avrg-rq size is 8K when this happens. avgqu-sz and await is also very high, causing many processes going into D state (including jdb2 thread) . I have also noticed KBDirty going high this time (658 MB in this case which is usually in few KBs otherwise), Am I hitting disk saturation?



      SAR Memory Usage:======================================
      Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)
      11:29:20    kbmemfree kbmemused  %memused kbbuffers  kbcached  kbcommit   %commit  kbactive   kbinact   kbdirty
      11:29:21     80270488  52009236     39.32    354368  17373312  15789156      7.92  10257860  15388656    658488
      Average:     80270488  52009236     39.32    354368  17373312  15789156      7.92  10257860  15388656    658488

      SAR IO Usage:======================================
      Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)

      11:29:22          tps      rtps      wtps   bread/s   bwrtn/s
      11:29:23       351.00      0.00    351.00      0.00   2808.00
      Average:       351.00      0.00    351.00      0.00   2808.00

      SAR Device IO activity:======================================
      Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)

      11:29:23          DEV       tps  rd_sec/s  wr_sec/s  avgrq-sz  avgqu-sz     await     svctm     %util
      11:29:24        loop5      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
      11:29:24          sda    285.00      0.00   2280.00      8.00    143.51    510.94      3.51    100.00
      11:29:24        vault      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
      Average:          DEV       tps  rd_sec/s  wr_sec/s  avgrq-sz  avgqu-sz     await     svctm     %util

      Average:        loop5      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
      Average:          sda    285.00      0.00   2280.00      8.00    143.51    510.94      3.51    100.00
      Average:        vault      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00

      SAR Queue and Load avg:======================================
      Linux 4.9.86     01/07/19        _x86_64_        (32 CPU)

      11:29:25      runq-sz  plist-sz   ldavg-1   ldavg-5  ldavg-15   blocked
      11:29:26            0      1043      3.39      2.30      2.15         2
      Average:            0      1043      3.39      2.30      2.15         2


      the file system mounted as ext3 with ext4 driver, data=ordered,barrier=0 setting with journaling enabled.



      Raid configuration:




        Model:SAS2008 Firmware Version: 9.00.00.00 RAID Level:RAID1
       








      filesystems ext3 journaling






      share|improve this question















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      share|improve this question




      share|improve this question








      edited Jan 8 at 20:10









      guntbert

      1,04911017




      1,04911017










      asked Jan 8 at 19:44









      PKB85PKB85

      113




      113




















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          This looks like what you'd expect to see if process were to send a lot of non-sequential (random) small writes. You'd have a relatively small average request size (8, which probably means 8×512 byte sectors = 4K, so the minimum with normal writes). Having more dirty buffers also is consistent, it means the writes have been passed off to the kernel & the kernel is working on writing them to disk. 285 tps is pretty darn nice performance for a magnetic disk.



          You need to investigate what programs are writing to disk and see if they're exhibiting abnormal behavior. Or if the programs can be configured to spread write better (e.g., if it's a database, the dirty page writeback speed is often configurable).



          ext3 isn't really recommended for, well, anything. ext4 is a conservative choice for a replacement (but with barrier=0, you're clearly not concerned about that); XFS is another good choice (and still very reliable). But I doubt that'll really help here. SSDs, though, certainly will give far higher IOPS.






          share|improve this answer























          • thanks. the issue is more frequent after kernel upgrade from 3.x to 4.9.86. I have noticed one weird thing after this upgrade. the mount point was in writeback mode in 3.x kernel (using ext3 driver) which got changed to ordered mode (using ext4 driver but fs mounted as ext3). Can this be a factor?

            – PKB85
            Jan 9 at 16:52











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          This looks like what you'd expect to see if process were to send a lot of non-sequential (random) small writes. You'd have a relatively small average request size (8, which probably means 8×512 byte sectors = 4K, so the minimum with normal writes). Having more dirty buffers also is consistent, it means the writes have been passed off to the kernel & the kernel is working on writing them to disk. 285 tps is pretty darn nice performance for a magnetic disk.



          You need to investigate what programs are writing to disk and see if they're exhibiting abnormal behavior. Or if the programs can be configured to spread write better (e.g., if it's a database, the dirty page writeback speed is often configurable).



          ext3 isn't really recommended for, well, anything. ext4 is a conservative choice for a replacement (but with barrier=0, you're clearly not concerned about that); XFS is another good choice (and still very reliable). But I doubt that'll really help here. SSDs, though, certainly will give far higher IOPS.






          share|improve this answer























          • thanks. the issue is more frequent after kernel upgrade from 3.x to 4.9.86. I have noticed one weird thing after this upgrade. the mount point was in writeback mode in 3.x kernel (using ext3 driver) which got changed to ordered mode (using ext4 driver but fs mounted as ext3). Can this be a factor?

            – PKB85
            Jan 9 at 16:52
















          0














          This looks like what you'd expect to see if process were to send a lot of non-sequential (random) small writes. You'd have a relatively small average request size (8, which probably means 8×512 byte sectors = 4K, so the minimum with normal writes). Having more dirty buffers also is consistent, it means the writes have been passed off to the kernel & the kernel is working on writing them to disk. 285 tps is pretty darn nice performance for a magnetic disk.



          You need to investigate what programs are writing to disk and see if they're exhibiting abnormal behavior. Or if the programs can be configured to spread write better (e.g., if it's a database, the dirty page writeback speed is often configurable).



          ext3 isn't really recommended for, well, anything. ext4 is a conservative choice for a replacement (but with barrier=0, you're clearly not concerned about that); XFS is another good choice (and still very reliable). But I doubt that'll really help here. SSDs, though, certainly will give far higher IOPS.






          share|improve this answer























          • thanks. the issue is more frequent after kernel upgrade from 3.x to 4.9.86. I have noticed one weird thing after this upgrade. the mount point was in writeback mode in 3.x kernel (using ext3 driver) which got changed to ordered mode (using ext4 driver but fs mounted as ext3). Can this be a factor?

            – PKB85
            Jan 9 at 16:52














          0












          0








          0







          This looks like what you'd expect to see if process were to send a lot of non-sequential (random) small writes. You'd have a relatively small average request size (8, which probably means 8×512 byte sectors = 4K, so the minimum with normal writes). Having more dirty buffers also is consistent, it means the writes have been passed off to the kernel & the kernel is working on writing them to disk. 285 tps is pretty darn nice performance for a magnetic disk.



          You need to investigate what programs are writing to disk and see if they're exhibiting abnormal behavior. Or if the programs can be configured to spread write better (e.g., if it's a database, the dirty page writeback speed is often configurable).



          ext3 isn't really recommended for, well, anything. ext4 is a conservative choice for a replacement (but with barrier=0, you're clearly not concerned about that); XFS is another good choice (and still very reliable). But I doubt that'll really help here. SSDs, though, certainly will give far higher IOPS.






          share|improve this answer













          This looks like what you'd expect to see if process were to send a lot of non-sequential (random) small writes. You'd have a relatively small average request size (8, which probably means 8×512 byte sectors = 4K, so the minimum with normal writes). Having more dirty buffers also is consistent, it means the writes have been passed off to the kernel & the kernel is working on writing them to disk. 285 tps is pretty darn nice performance for a magnetic disk.



          You need to investigate what programs are writing to disk and see if they're exhibiting abnormal behavior. Or if the programs can be configured to spread write better (e.g., if it's a database, the dirty page writeback speed is often configurable).



          ext3 isn't really recommended for, well, anything. ext4 is a conservative choice for a replacement (but with barrier=0, you're clearly not concerned about that); XFS is another good choice (and still very reliable). But I doubt that'll really help here. SSDs, though, certainly will give far higher IOPS.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Jan 8 at 21:15









          derobertderobert

          73k8153210




          73k8153210












          • thanks. the issue is more frequent after kernel upgrade from 3.x to 4.9.86. I have noticed one weird thing after this upgrade. the mount point was in writeback mode in 3.x kernel (using ext3 driver) which got changed to ordered mode (using ext4 driver but fs mounted as ext3). Can this be a factor?

            – PKB85
            Jan 9 at 16:52


















          • thanks. the issue is more frequent after kernel upgrade from 3.x to 4.9.86. I have noticed one weird thing after this upgrade. the mount point was in writeback mode in 3.x kernel (using ext3 driver) which got changed to ordered mode (using ext4 driver but fs mounted as ext3). Can this be a factor?

            – PKB85
            Jan 9 at 16:52

















          thanks. the issue is more frequent after kernel upgrade from 3.x to 4.9.86. I have noticed one weird thing after this upgrade. the mount point was in writeback mode in 3.x kernel (using ext3 driver) which got changed to ordered mode (using ext4 driver but fs mounted as ext3). Can this be a factor?

          – PKB85
          Jan 9 at 16:52






          thanks. the issue is more frequent after kernel upgrade from 3.x to 4.9.86. I have noticed one weird thing after this upgrade. the mount point was in writeback mode in 3.x kernel (using ext3 driver) which got changed to ordered mode (using ext4 driver but fs mounted as ext3). Can this be a factor?

          – PKB85
          Jan 9 at 16:52


















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