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Basic Storage Service Configuration Guide for File

OceanStor V3 Series V300R006

This document is applicable to OceanStor 2200 V3, 2600 V3, 5300 V3, 5500 V3, 5600 V3, 5800 V3, 6800 V3, 18500 V3, and 18800 V3. It describes the basic storage services and explains how to configure and manage them.
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Write Mode Changing from Write Back to Write Through

Write Mode Changing from Write Back to Write Through

The default write mode of file systems in a storage system is write back. However, the write mode will become write through in the event of a fault.

Table 1-3 Scenarios where the write mode of file systems changes from write back to write through and recommended actions

Symptom

Scenario

Impact and Recommended Action

The temperature of a controller exceeds the upper limit.

  • If the Controller Enclosure Temperature Exceeds The Upper Limit alarm is generated due to an exception in the equipment room temperature or the internal components of a storage system, file systems remain in write back mode for a specified period of time (192 hours by default). If the alarm persists after the specified period of time, the mode changes to write through.
  • If the Controller Enclosure Temperature Exceeds The Upper Limit alarm is generated due to a fault on a single controller, file systems remain in write back mode for a specified period of time (1 hour by default). If the alarm persists after the specified period of time, the mode changes to write through.
NOTE:

If the Controller Enclosure Temperature Is Far Beyond The Upper Limit alarm is generated in a storage system, the storage system will automatically power off.

  • Impact

    The write mode of all file systems belonging to the controller enclosure changes to write through after the specified period of time.

  • Recommended action

    Check the external refrigerating system, fan modules, and air channels to locate the cause of the overtemperature alarm and rectify faults.

BBUs on a controller enclosure malfunction.

  • Dual-controller storage system: If two BBUs malfunction and an alarm is generated, the write mode changes from write back to write through.
  • Four-controller storage system: If two or more BBUs malfunction and an alarm is generated, the write mode changes from write back to write through.
  • Impact

    The write mode of all file systems belonging to the controller enclosure changes to write through.

  • Recommended action
    • Check whether BBUs are properly inserted.
    • Check whether the BBUs are faulty and replace them if necessary.
    • Check whether the charge of the BBUs is insufficient. If the power of the BBUs is insufficient, wait until the BBUs are fully charged.

The coffer disks of a controller enclosure malfunction.

  • Dual-controller storage system: If all coffer disks break down, the write mode changes from write back to write through.
  • Four-controller storage system: If all coffer disks of controllers A and B or controllers C and D break down (the controllers in the first row are controllers A and B and the controllers in the second row are controllers C and D), the write mode changes from write back to write through.
  • Impact

    The write mode of all file systems belonging to the controller enclosure changes to write through.

  • Recommended action

    Replace coffer disks.

A controller malfunctions.

If a single controller malfunctions, file systems remain in write back mode for a specified period of time (192 hours by default). If the fault is not rectified within this period, the write mode changes from write back to write through.

  • Impact

    The write mode of all file systems belonging to the controller enclosure changes to write through if the fault persists after 192 hours.

  • Recommended action
    • Replace the faulty controller during off-peak hours and within the 192 hour period after the malfunction.
    • If a spare part is unavailable during the write back protection period, extend the time after assessing risks to prevent write through from adversely affecting service performance.

The remaining capacity of a file system is smaller than the threshold.

If the remaining capacity of a file system is smaller than the threshold, an alarm will be generated. If the remaining space is about to be exhausted, the file system's write mode changes to write through by default, but you can run the following command in developer mode to change write through to space exhaustion protection: change file_system optimization file_system_id=? name=space_exhaust_protect enabled=yes. For details, see the advanced O&M command reference of the corresponding product model.

NOTE:

In the following scenario, the data write mode of a file system changes to write through due to insufficient file system capacity:

Used capacity of a file system + Capacity that grains occupy (including space debris, space prefetch, delayed release space) + Capacity of dirty data in cache > Total capacity of a file system

However, the system may not generate an alarm indicating that the remaining capacity of the file system is smaller than the threshold.

  • Impact

    After the write mode of the file system changes to write through, the performance of the file system deteriorates.

  • Recommended action

    Expand the file system.

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Updated: 2019-07-12

Document ID: EDOC1000138856

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