Automatic background TRIM
IBM Spectrum® Scale supports automatic reclamation of free space when it is available after deletion.
This operation can be enabled by setting the backgroundSpaceReclaimThreshold parameter. The parameter specifies the percentage of reclaimable blocks that must occur in an allocation space for devices capable of space reclaim, such as NVMe and thin provisioned disks, to trigger a background space reclaim. The default value is 0 that indicates the background space reclamation is disabled. You can enable it by setting it to a value greater than 0 but less than or equal to 100. If a lower value is set, the free space is reclaimed frequently.
The lower value is disabled by default. Use the mmchconfig command to enable it. This parameter can be set at the cluster level. Therefore, it is recommended that the setting of backgroundSpaceReclaimThreshold only be applied on node-class or individual IBM Storage Scale node basis for the platforms in the following table. For more information about the backgroundSpaceReclaimThreshold parameter see, mmchconfig command in IBM Storage Scale: Command Reference.
This table does not contain IBM Storage Scale RAID platforms that do not support the NVMe-based storage. To enable TRIM, see Managing TRIM support for storage space reclamation.
| IBM Storage Scale RAID platforms | The backgroundSpaceReclaimThreshold parameter value | Comments and limitations |
|---|---|---|
| ESS 3000 | 01 | Background TRIM is not supported. |
| ESS 3200 | 15 | Background TRIM might degrade the performance of certain write workloads*. |
| ESS 3500 (performance/hybrid only) | 15 | Background TRIM might degrade the performance of certain write workloads*. |
| 1 This is a default value. When you want to disable the enabled background TRIM, set the value to 0 again. | ||
| * The space reclamation, whether background or manual, affects write workloads that allocate new blocks from the file system. For example, when you create and populate new files. If such workloads are the primary use case or occur at unscheduled times, then the automatic background file system TRIM might not be the best fit for such an environment. It is recommended to verify backgroundSpaceReclaimThreshold in your environment. Additionally, the setting can be disabled dynamically at any time. For more information about TRIM configuration, see Best practices for TRIM configurations. | ||