CloudStack and Hypervisors: Comparing KVM, Xen, and VMware

CloudStack supports three main hypervisors, KVM, XenServer, and VMware (vSphere/ESXi). Each integrates differently with the CloudStack management plane.

Overview

1. KVM with CloudStack

Architecture Diagram

                +------------------------+
                |   CloudStack Mgmt      |
                |  (Management Server)   |
                +-----------+------------+
                            |
                            |  SSH / Agent API
                            v
     -------------------------------------------------------
     |                       |                      |
     v                       v                      v
+-----------+         +-----------+          +-----------+
| KVM Host1 |         | KVM Host2 |          | KVM Host3 |
| (libvirt) |         | (libvirt) |          | (libvirt) |
+-----------+         +-----------+          +-----------+
     |                       |                      |
     +--- CloudStack Agent running on each host ----+
     |
     +-- Bridge Interfaces (cloudbr0 / virbr0 / ovsbr0)
     |
     +-- Link Local network for System VM control
     |
     +-- Shared Storage (NFS / SharedMountPoint / OCFS2 / CLVM / GFS2)

2. XenServer with CloudStack

Architecture Diagram

                +------------------------+
                |    CloudStack Mgmt     |
                |  (Management Server)   |
                +----------+-------------+
                           |
                           | API / SSH
                           v
              +------------+-------------+
              |  XenServer Pool Master   |  ← CloudStack connects ONLY here
              +------------+-------------+
                           |
     ---------------------------------------------------------
     |                       |                       |
     v                       v                       v
+-----------+         +-----------+          +-----------+
|  Host 1   |         |  Host 2   |          |  Host 3   |
|  (in pool)|         |  (in pool)|          |  (in pool)|
+-----------+         +-----------+          +-----------+
     |                       |                       |
     +-- Link Local Network --+-----------------------+
     |      (for System VMs & Virtual Routers)        |
     --------------------------------------------------
                           |
                           v
                +------------------------+
                |   Storage Repositories |
                | (NFS, iSCSI, FC, etc.)|
                +------------------------+

3. VMware (vSphere/ESXi) with CloudStack

Architecture Diagram

               +-------------------------+
               |   CloudStack Mgmt       |
               +-----------+-------------+
                           |
                           | vCenter API (HTTPS / 443)
                           v
              +------------+------------+
              |      vCenter Server      |
              +------------+-------------+
                           |
        ---------------------------------------------
        |                      |                   |
        v                      v                   v
+-------------+         +-------------+     +-------------+
|   ESXi Host |         |   ESXi Host |     |   ESXi Host |
+-------------+         +-------------+     +-------------+
        |                      |                   |
        +-- Managed via vSwitch/dvSwitch Network --+
        |
        +-- Shared Storage (Datastores: NFS / iSCSI / FC)

Comparison Summary

Conclusion

Each hypervisor in CloudStack serves a specific purpose:

• KVM → Best for open-source, flexible environments.
• XenServer → Suited for Citrix-based setups needing managed pools.
• VMware → Ideal where vCenter is already in use.