Virtualization

Understanding the sync and async phases of VM deployment. SYNC PHASE (~250ms) Client blocks here. Must complete before job ID is returned. ┌─────────────────────────────────────────────────────────────────────────┐ │ SYNC PHASE (37.044 - 37.296) ~250ms │ ├─────────────────────────────────────────────────────────────────────────┤ │ │ │ HTTP POST /deployVirtualMachine │ │ │ │ │ ▼ │ │ ┌─────────────────┐ │ │ │ Authentication │ 2FA check, CIDR validation │ │ │ Authorization │ Role check, resource permissions │ │ └────────┬────────┘ │ │ ▼ │ │ ┌─────────────────┐ │ │ │ DB Allocation │ vm_instance (Stopped), nics, volumes (Allocated) │ │ │ │ resource_count incremented │ │ └────────┬────────┘ │ │ ▼ │ │ ┌─────────────────┐ │ │ │ Submit Job │ AsyncJobManager creates job-43 │ │ └────────┬────────┘ │ │ ▼ │ │ Return: { jobid: "5dc96a21-....

Both VPCs and Isolated Networks in Apache CloudStack provide Layer-3 network isolation for user VMs, but they differ in design and use cases. Isolated Network An Isolated Network is a single, flat network with one virtual router. All VMs share the same subnet and routing domain. Key points: One subnet per network (e.g., 10.1.1.0/24). One virtual router handles NAT, DHCP, and firewall rules. No inter-tier routing; traffic is flat. Ideal for single-tier applications or quick deployments....

Snapshots in Apache CloudStack can exist at two levels — VM snapshots and volume snapshots — each serving different purposes and stored in different locations. VM Snapshots A VM snapshot is a hypervisor-level checkpoint of an entire virtual machine. It captures the VM’s disk state and optionally its memory, allowing fast rollback to a previous state. Key points: Stored on primary storage. Created quickly without full data copy. Can include memory state for live restore....

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)....