Understanding the factors that affect the maximum rate of exporting a VM to OVF

Products

• VMware vSphere ESXi

Issue/Introduction

Exporting a VM to OVF is slow, throttling to XX MB/s. Keep in mind that the maximum speed varies for each individual, and results may differ depending on various factors.

Resolution

Part of the export VM where is the most limiting is storage, and CPU to get the VM's disks ready to be sent over the network to client. This process includes the followings,

- to read the disk from storage grain by grain into a buffer
- compress that buffer to a compressed buffer using gzip compression library
- then send over the compressed buffer to client using HTTP layer

Key things that play a role is:
- CPU 
- storage performance
- layout of the VMDK
- compression time
- network performance

The process is multi-variable and varies in performance.  So depending on the hardware/storage/network performance will be different.

Transferring a file from ESXi using HTTP is not the same as changing a VMDK of a VM into StreamOptimized(compressed) format and pushing it out on HTTP layer.  You will never get the same performance for the two cases aforementioned. If that is the expectation it is not realistic.