ALM-12180 Suspended Disk I/O

Alarm Description

For MRS 3.3.0 and its later versions as well as MRS 3.1.0.0.10/3.1.5.0.3 and later patch versions:

• For HDDs, the alarm is triggered when any of the following conditions is met:
  • By default, the system collects data every 3 seconds. The svctm latency reaches 6 seconds within 30 seconds in at least seven collection periods.
  • By default, the system collects data every 3 seconds. The disk queue depth (avgqu-sz) is greater than 0, the IOPS or bandwidth is 0, and ioutil is greater than 99% in at least 10 collection periods within 30 seconds.
  • By default, the system collects data every 3 seconds. At least 50% of detected svctm take no less than 1000 ms within 300 seconds.
• For SSDs, the alarm is triggered when any of the following conditions is met:
  • By default, the system collects data every 3 seconds. The svctm latency reaches 3 seconds within 30 seconds in at least seven collection periods.
  • By default, the system collects data every 3 seconds. The disk queue depth (avgqu-sz) is greater than 0, the IOPS or bandwidth is 0, and ioutil is greater than 99% in at least 10 collection periods within 30 seconds.
  • By default, the system collects data every 3 seconds. At least 50% of detected svctm take no less than 500 ms within 300 seconds.

The collection period is 3 seconds, and the detection period is 30 or 300 seconds. This alarm is automatically cleared when neither of the preceding conditions is met for three consecutive detection periods (30 or 300 seconds).

For versions earlier than MRS 3.3.0:

• For HDDs, the alarm is triggered when any of the following conditions is met:
  • By default, the system collects data every 3 seconds. The svctm latency exceeds 6 seconds within 30 seconds in at least 10 collection periods.
  • By default, the system collects data every 3 seconds. The disk queue depth (avgqu-sz) is greater than 0, the IOPS or bandwidth is 0, and ioutil is greater than 99% in at least 10 collection periods within 30 seconds.
• For SSDs, the alarm is triggered when any of the following conditions is met:
  • By default, the system collects data every 3 seconds. The svctm latency exceeds 2 seconds within 30 seconds in at least 10 collection periods.
  • By default, the system collects data every 3 seconds. The disk queue depth (avgqu-sz) is greater than 0, the IOPS or bandwidth is 0, and ioutil is greater than 99% in at least 10 collection periods within 30 seconds.

This alarm is automatically cleared when the preceding conditions have not been met for 90s.

For details about how to obtain and calculate related parameters, see Related Information.

Alarm Attributes

Alarm Parameters

Impact on the System

If the I/O usage keeps increasing, operations will be affected and services will be interrupted. The possible impacts are as follows:

• The system I/O performance deteriorates, which means slow response and low throughput. For example, job submission is slow, page responds slowly, interface response times out, and the system is in error or even crash.
• Customer services may be interrupted. The system may break down and the key information stored on the faulty disk may be lost.

Possible Causes

The disk is aged.

Handling Procedure

Replace the disk.

1. Log in to FusionInsight Manager and choose O&M > Alarm > Alarms.
2. View the detailed information about the alarm. Check the values of HostName and DiskName in the location information to obtain the information about the faulty disk for which the alarm is reported.
3. Replace the hard disk.
4. Check whether the alarm is cleared.
   • If yes, no further action is required.
   • If no, go to 5.

Collect fault information.

5. On FusionInsight Manager, choose O&M. In the navigation pane on the left, choose Log > Download.
6. Select OMS for Service and click OK.
7. Click in the upper right corner, and set Start Date and End Date for log collection to 10 minutes ahead of and after the alarm generation time, respectively. Then, click Download.
8. Contact O&M personnel and provide the collected logs.

Alarm Clearance

This alarm is automatically cleared after the fault is rectified.

Related Information

Obtain and calculate related parameters as follows:

• Run the following command in the OS to collect data:

  iostat -x -t 1 1

  

  Parameters are as follows:

  avgqu-sz indicates the disk queue depth.

  The sum of r/s and w/s is the IOPS.

  The sum of rkB/s and wkB/s is the bandwidth.

  %util is the ioutil value.

• MRS 3.1.0:

  Run the iostat -x -t command in the OS.

  

• Calculate svctm as follows in versions later than MRS 3.1.0:

  svctm = (tot_ticks_new - tot_ticks_old) / (rd_ios_new + wr_ios_new - rd_ios_old - wr_ios_old)

• Versions earlier than MRS 3.3.0: If rd_ios_new + wr_ios_new - rd_ios_old - wr_ios_old = 0, then svctm = 0.
• MRS 3.3.0 and its later versions as well as MRS 3.1.0.0.10/3.1.5.0.3 and later patch versions:

  When the detection period is 30 seconds, if rd_ios_new + wr_ios_new - rd_ios_old - wr_ios_old = 0, then svctm = 0.

  When the detection period is 300 seconds and rd_ios_new + wr_ios_new - rd_ios_old - wr_ios_old = 0, if tot_ticks_new - tot_ticks_old = 0, then svctm = 0; otherwise, the value of svctm is infinite.

The parameters can be obtained as follows:

The system runs the cat /proc/diskstats command every 3 seconds to collect data. For example:

In the two commands:

In the data collected for the first time, the number in the fourth column is the rd_ios_old value, the number in the eighth column is the wr_ios_old value, and the number in the thirteenth column is the tot_ticks_old value.

In the data collected for the second time, the number in the fourth column is the rd_ios_new value, the number in the eighth column is the wr_ios_new value, and the number in the thirteenth column is the tot_ticks_new value.

In this case, the value of svctm is as follows:

(19571460 - 19569526) / (1101553 + 28747977 - 1101553 - 28744856) = 0.6197