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Sudden latency and CPU utilization from workloads

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Applies to

  • ONTAP 9
  • ONTAP Select v9.12.1 or higher
  • FAS/AFF systems
  • Cluster Volume ONTAP (CVO)

Issue

  • Central Processing Unit (CPU) is high, near or at 100% constantly, or increased CPU utilization above the expected level which can be seen even during firmware upgrade process when nodes takeover and giveback
  • Performance capacity alert triggered on the node.
  • Write Anywhere File Layout (WAFL) WAFL_Ex may be one of the busiest domains (where Data Processing happens).
  • Hosts report high IO wait times for a particular duration in a day.
  • The command sysstat -M 1 can be used to check the busiest domain. 
  • For Network File System (NFS )clients, this may be indicated by "NFS server not responding" errors.
  • When the cluster is monitored by Active IQ Unified Manager, the following alert can be triggered.

Incident - Node Utilization Critical Threshold Breached
Impact Area - Performance
Severity - Critical
State - New
Source - Cluster01-02
Cluster Name - Cluster01
Cluster FQDN - 10.0.0.X
Trigger Condition - Utilization value of 98% on Cluster01-02 has triggered a CRITICAL event based on threshold setting of 90%.

  • Virtual Desktop Infrastructure (VDI) users will be experiencing read/write/other  latency issues seen from the active IQ graph as below for the impacted volume.

image (72)_.png

Example: sysstat output shows CPU rising due to an increase in user workload (columns removed for readability)

Cluster::> node run -node <node> -command sysstat -x 1
 CPU    NFS   CIFS   HTTP   Total     Net   kB/s     HDD   kB/s
                                       in    out    read  write
 11%    1324     0      0    1324     169    131    5300      0
 28%      72     0      0      72     483    526    4928     12
 53%     175     0      0     175     254    407    5176     24
 23%     143     0      0     143     146     72    4752      0
 12%     230     0      0     230     134    259    5808     24
 40%    5766     0      0    5766     207    720   44336  36956
 53%     108     0      0     108   15698  14391   32340     24
 46%      30     0      0      30   30975  30269   29900      0
 87%   32124     0      0   32124  576397  53287  203513     12
 99%   44334     0      0   44334  659406  45518  256931 251353
 99%   43692     0      0   43692  609739  16930  263599 565448
 99%   44492     0      0   44492  633509  41562  261366 116257

 

 

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