Enabling unmap for NVMe devices (NVMe over FC & NVMe over TCP)
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Enabling unmap for NVMe devices (NVMe over FC & NVMe over TCP)

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Article ID: 394789

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Updated On:

Products

VMware vSphere ESXi

Issue/Introduction

  • VMFS6 datastores backed by NVMe devices, NVMe over FC or NVMe over TCP
  • Space is not being reclaimed automatically for these devices in 8.0U2 & U3 

Environment

VMware vSphere ESXi 8.0U2 and U3

Cause

  • Space allocation is not enabled on the ESXi hosts by default.
  • /Scsi/NvmeUseDsmTp4040 default value is 0

Resolution

To enable unmap for NVMe in 8.0U2 & U3 follow the below steps:

  1. Log into the ESXi host, verify that NVMe DSM is disabled:

    # esxcfg-advcfg -g /Scsi/NvmeUseDsmTp4040
    The expected value is 0.

  2. Enable NVMe DSM:

    # esxcfg-advcfg -s 1 /Scsi/NvmeUseDsmTp4040

  3. Verify that the DSM is enabled:

    # esxcfg-advcfg -g /Scsi/NvmeUseDsmTp4040

    The expected value is 1.

  4. After enabling NVMe DSM for all new datastores created backed by NVMe devices will automatically release unused blocks, however for  existing datastores a force reclaim is required by running the below command.

    # esxcli storage core claiming reclaim -d <namespace_uuid>

  5. Alternatively you can reboot the host as well.

As of 9.x this option is automatically enabled .

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