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Updated on 2022-08-10 GMT+08:00

What Is Reserved Memory? How Do I Configure Reserved Memory?

Reserved Memory

Reserved memory is part of the memory that is not used for storing data, but for data persistence, master/standby synchronization, and backup.

Parameter reserved-memory-percent is used for configuring reserved memory.

In the monitoring data, the memory usage does not include the usage of reserved memory.

Only the following instances must have reserved memory:

  • Single-node DCS Redis 3.0 instances
  • Master/standby DCS Redis 3.0 instances
  • Single-node DCS Memcached instances
  • Master/standby DCS Memcached instances

If reserved memory is insufficient because data occupies too much memory, the following problems may occur:

  • Operations on the DCS instance become slow. (The system enables swap, deteriorating the performance.)
  • Data cannot be backed up.
  • Data cannot be synchronized between the master and standby nodes in time.
  • Instance specifications cannot be changed.
  • The process may restart.

Procedure for Configuring Reserved Memory

Change the value of reserved-memory-percent by referring to Modifying Configuration Parameters of an Instance.

  • Set the parameter to at least 30. For instances created in or after 2021, the default value is 30.
  • The percentage takes the maximum available memory, rather than the total memory, as the whole. The available memory is listed in the Available Memory column in DCS Instance Specifications.

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