Configuring periodic storage space reclamation for a virtual machine

The AVE virtual machine allows the guest operating system to trigger the space reclamation action of its corresponding ABS storage through the TRIM instruction. If space is reclaimed by triggering the TRIM command each time data is deleted, the latency overhead of the deletion will be high and may have an impact on the performance of the virtual disk. Therefore, it is recommended to configure periodic storage space reclamation for virtual machines.

Prerequisite

• The provisioning type for virtual volumes is thin provisioning.
• The operating system of the virtual machine supports the storage space reclamation feature, and the tested and verified operating systems and versions can be found in Storage space reclamation compatibility list.

Precaution

• In a virtual machine containing both thin-provisioned and thick-provisioned virtual volumes, only the thin-provisioned volumes support this function.
• For Linux virtual machines using virtio-blk devices, it is recommended to use operating systems with a mainline kernel version of v5.19 or later. Operating systems with a mainline kernel version earlier than v5.0 do not support the discard command. For kernel versions earlier than v5.19, the discard_granularity parameter is forcibly set to 512, which may lead to abnormal discard behavior. The 3.10 kernel used by CentOS 7 does not support discard. However, the 4.18+ kernels used by CentOS 8 and 9 include backported patches from the mainline kernel, thereby supporting discard. For detailed operating system compatibility, refer to Storage space reclamation compatibility list. Linux virtual machines using virtio-scsi devices are not affected by this issue and can reclaim storage space normally.