After upgrading to ESXi 7.0 or ESXi 6.7P05, large IOs will fail if DiskMaxIOSize is set too low

Products

• VMware vSphere ESXi
• VMware vSphere ESXi 6.0
• VMware vSphere ESXi 7.0

Issue/Introduction

Symptoms:
When DiskMaxIOSize is set to a value of 512k or lower, larger IOs will fail and be aborted by the driver with an issue time of zero or close to zero seconds. Here is an example from Cisco's Native FNIC (NFNIC) driver:

nfnic: <2>: INFO: fnic_abort_cmd: 3548: Abort cmd called for Tag: 0x33d  issued time: 0 ms CMD_STATE: FNIC_IOREQ_CMD_PENDING CDB Opcode: 0x2a  sc:0x459a81b31340 flags: 0x3 lun: 3 target: 0x320540
nfnic: <2>: INFO: fnic_abort_cmd: 3548: Abort cmd called for Tag: 0x368  issued time: 0 ms CMD_STATE: FNIC_IOREQ_CMD_PENDING CDB Opcode: 0x28  sc:0x45ba8a22dc80 flags: 0x3 lun: 12 target: 0x320540
nfnic: <2>: INFO: fnic_abort_cmd: 3548: Abort cmd called for Tag: 0x38a  issued time: 0 ms CMD_STATE: FNIC_IOREQ_CMD_PENDING CDB Opcode: 0x28  sc:0x45ba8a2cd280 flags: 0x3 lun: 3 target: 0x320540
nfnic: <2>: INFO: fnic_abort_cmd: 3548: Abort cmd called for Tag: 0x3e5  issued time: 0 ms CMD_STATE: FNIC_IOREQ_CMD_PENDING CDB Opcode: 0x28  sc:0x45ba8a2cd640 flags: 0x3 lun: 3 target: 0x320540

Environment

VMware vSphere ESXi 7.0.x
VMware vSphere ESXi 6.7.x

Cause

In ESXi 7.0 and ESXi 6.7P05, if the DiskMaxIOSize is set to 512KB or lower, the commands will not split and the IOs will immediately fail.

Resolution

This issue has been resolved in ESXi 7.0 Update 2c as well as ESXi 6.7P06

Workaround:
To workaround this issue, it is recommended to set the DiskMaxIOSize back to the default of 32M.