ZStack Cloud Resource Model

ZStack Cloud is essentially a configuration management system for resources in the Cloud. The following figure describes the resource model managed by ZStack Cloud, as shown in Figure 1.

ZStack Cloud mainly has the following resources:

Zone: the largest resource scope defined in ZStack Cloud. A zone is a logical group of resources, such as clusters, L2 networks, and primary storages.
Cluster: a logical group of analogy hosts (compute nodes).
Host: also known as a compute node, is a physical server that provides VM instances with compute, network, and storage resources.
Primary storage: a storage system that stores VM disk files, including root volumes, data volumes, root volume snapshots, data volume snapshots, and image caches. Supported primary storage types include local storage, NFS, SharedMountPoint, SharedBlock, and Ceph.
Backup storage: a storage system that stores image templates. Supported backup storage types include ImageStore, SFTP, and Ceph.
VXLAN pool: an underlay network in VXLAN. You can create multiple VXLAN overlay networks (VXLAN) in a VXLAN pool. The overlay networks can operate on the same underlay network device. Supported VXLAN pool types include software SDN and hardware SDN.
L2 network: a layer 2 broadcast domain used for layer 2 isolation. Generally, L2 networks are identified by names of devices on the physical network. Supported L2 network types include L2NoVlanNetwork, L2VlanNetwork, VxlanNetwork, and HardwareVxlanNetwork.
L3 network: a collection of network configurations for VM instances, including the IP range, gateway, DNS, and network services.
Instance offering: a specification that defines the number or size of CPU, memory, disk bandwidth, and network bandwidth for a VM instance.
Disk offering: a specification of a volume, which defines the size of a volume and how the volume will be created.
VM instance: a virtual machine instance running on a host. A VM instance has its own IP address to access public network and run application services. VM instances are core components of ZStack Cloud.
Image: an image template used by a VM instance or volume. Image template includes root volume images and data volume images. The types of root volume image include ISO and Image, while the type of data volume image is Image.
Root volume: the system disk where the VM operating system is installed.
Data volume: the data disk that provides additional storage for a VM instance.
Snapshot: a point-in-time capture of data in a disk. Snapshots are captured incrementally.
Network service module: a module for providing network services. This resource is hidden in the UI.
Network service: provides various network services for VM instances, including VPC firewall, security group, virtual IP (VIP), elastic IP (EIP), port forwarding, load balancing, IPsec tunnel, and flow monitoring.
VPC firewall: manages north-south traffic of the VPC network. You can manage the network access policy by configuring rule sets and rules.
Security group: provides L3 network firewall control over the VM instances, and controls TCP, UDP, and ICMP data packets for effective filtering. You can use a security group to effectively control specified VM instances on specified networks according to specified security rules.
vRouter offering: an instance offering that defines the number of vCPU cores, memory size, image, management network, and public network configuration settings of VPC vRouters.
VPC vRouter: a router created directly from a vRouter offering. VPC vRouter, which has a public network and a management network, is the core of VPC. VPC vRouters provide various network services, including DHCP, DNS, SNAT, route table, EIP, port forwarding, load balancing, IPsec tunnel, dynamic routing, multicast routing, VPC firewall, and Netflow.

The resource relationships in ZStack Cloud are as follows:

Parent-child: A resource can be the parent or child of another resource. For example, a host is the child resource of a cluster and the parent resource of a VM instance.
Sibling: Resources sharing the same parent resource are siblings. For example, clusters and L2 networks are sibling resources because all of them are child resources of a zone.
Ancestor-descendant: A resource can be the lineal ancestor or lineal descendant of another resource. For example, a cluster is the ancestor resource of a VM instance, while a host is a descendant resource of a zone.
Friend: Resources that do not have the above three relationships but still need to cooperate with each other in some scenarios are friends. For example, primary storages and backup storages are friends. Also, zones and backup storages are friends.
Note: Relationship between primary storages and backup storages:
- When you create a VM instance, the primary storage needs to download images of the VM instance as caches from the backup storage.
- When you create an image, the primary storage needs to copy the root volume to the backup storage and save it as a template.

The following properties are common to almost all resources in ZStack Cloud:

UUID: the universally unique identifier. ZStack Cloud uses version 4 UUIDs to uniquely identify a resource.
Name: a human readable string that is used to identify resources. Names can be duplicated and are usually required.
Description: also known as a brief introduction that is used to briefly describe a resource. Description is usually optional.
Creation date: the date and time when a resource was created.
Last operation date: the date and time when a resource was updated last time.

Resources in ZStack Cloud support full or partial Create, Read, Update, Delete (CRUD) operations.

Create: create or add a new resource.
Read: read or query information about a resource.
Update: update information about a resource.
Delete: delete a resource. Due to the cascade framework provided by ZStack Cloud, if a parent resource is deleted, its associated child resources and descendant resources will also be deleted.

Resource Center

Resource Pool

VM Instance

A VM instance is a virtual machine instance running on a host. A VM instance has its own IP address and can access public networks and run application services.