Error: "Issue of delete blocks failed" is displayed in vmkernel.log file

Products

• VMware vSphere ESXi

Issue/Introduction

• In the /var/log/vmkernel.log file, you see entries similar to:
  
  FSDisk: 260: Issue of delete blocks failed [sync:0] numDescs 1 Address is not aligned on required boundary
  0x439dc0c5cb40
• hostd and/or vpxa process gets crashed due to random crypt failure.​

Environment

• VMware vSphere ESXi 5.5
• VMware ESXi 3.5.x Installable
• VMware ESXi 4.1.x Installable
• VMware ESXi 3.5.x Embedded
• VMware ESXi 4.0.x Installable
• VMware vSphere ESXi 5.0
• VMware ESXi 4.0.x Embedded
• VMware vSphere ESXi 5.1
• VMware vSphere ESXi 6.0
• VMware ESXi 4.1.x Embedded
• VMware vSphere ESXi 6.5

Cause

In the situation, Issue of delete blocks failed message is logged, ESXi can keep small memory data which should be released although this message itself is an informative and harmless. After a lot of this situation repeated, ESXi can exhaust a slab which is used to provide this memory data and it raises hostd/vpxa crash.

Resolution

This issue is resolved in,

• VMware ESXi 6.0 Patch 05.
• VMware ESXi 6.5 Update 1.

Workaround:

This can happen with RDM/VMFS backed LUNs. But if virtual RDM devices are configured, use one of these options:

• Use physical RDM instead of virtual RDM to the virtual machines.
• Disable the UNMAP commands from the guest operating system.

Note: UNMAP commands issued from the guest operating system are now supported on vSphere 6

Additional Information

Thin Provisioning Block Space Reclamation (VAAI UNMAP) does not work