GatewayServiceException: The operation failed with the error 'Memory allocation failed. Out of memory.'

Agentless VMware replication fails because the NFC buffer on the ESXi host is too small for the number of disks being replicated.

Why it happens

Microsoft says the appliance needs a 32 MB NFC buffer to replicate 8 disks at once on an ESXi host. If the host buffer is smaller, replication fails with this error.

How to fix it

1. 1

   Step 1

   Check with your VMware administrator before changing anything. Going above 32 MB can strain the host.

2. 2

   Step 2

   On the ESXi host, as root, raise maxMemory under <nfcsvc> in /etc/vmware/hostd/config.xml, then restart hostd and vpxa.

3. 3

   Step 3

   On the appliance, set HostBufferSizeInMB in %programdata%\Microsoft Azure\Config\GatewayDataWorker.json to the same value.

4. 4

   Step 4

   Restart the gateway service. Host and appliance values must match.

/etc/init.d/hostd restart
/etc/init.d/vpxa restart
net stop asrgwy
net start asrgwy

Source

Full guide: How to migrate VMware, Hyper-V and physical servers to Azure →