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1. Template / ISO Download Workflow When a user registers a new ISO or template via a URL, CloudStack offloads the download job to the Secondary Storage VM (SSVM). Step Action Component 1 User hosts ISO/template on HTTP server External (public web server) 2 User registers the URL CloudStack UI / API 3 CloudStack sends download job to SSVM Management Server 4 SSVM downloads the file via HTTP/HTTPS Secondary Storage VM (SSVM) 5 SSVM writes the file to secondary storage (NFS) /export/secondary on Management Server 6 CloudStack marks the template/ISO as “Ready” CloudStack Database Textual Flow Diagram +----------------------------+ | CloudStack Management | +-------------+--------------+ | Registers Template/ISO URL | v +-----------------------+ | Secondary Storage VM | (SSVM) +-----------+-----------+ | Downloads via HTTP/HTTPS | v +------------------------+ | Secondary Storage (NFS)| | /export/secondary | +------------------------+ | v Marks Template as READY 2....

CloudStack supports three main hypervisors, KVM, XenServer, and VMware (vSphere/ESXi). Each integrates differently with the CloudStack management plane. Overview Feature KVM XenServer VMware (vSphere) CloudStack connects to Each host directly Pool Master vCenter API System VM control Link Local network Link Local network Management network Networking Linux bridge / OVS Network labels vSwitch / dvSwitch Storage NFS / SharedMountPoint NFS / iSCSI / FC vCenter-managed datastores Max hosts/cluster Unlimited 64 (v7....

When CloudStack deploys a VM from a template, it uses a linked clone instead of creating a full copy of the disk. This approach saves both time and storage space. What Is a Linked Clone A linked clone is a virtual disk that shares the same base image as another VM or template. It doesn’t duplicate the full data. Instead: The base disk (template) is read-only. The linked clone stores only changes (writes made by the VM)....

Primary storage in CloudStack holds the root volumes of running virtual machines and data volumes attached to them. It operates at the cluster level — all hosts within a cluster share access to the same primary storage pool. Local Storage Each hypervisor uses its own local disk for VM volumes. There is no shared storage between hosts. Characteristics No need for expensive centralized SAN/NAS. Limited functionality — no live migration or HA....

CloudStack uses physical networks to separate different types of traffic within a zone. Each traffic type serves a specific purpose and can share or use dedicated network interfaces depending on deployment scale. Overview A physical network in CloudStack maps to one or more real NICs or bridges on the hypervisor hosts. Each physical network can carry multiple traffic types. Typical traffic types: Management Guest Public Storage Public and Storage networks might not exist in every deployment....