RH318 - ch02s05

After completing this section, students should be able to describe the use of storage domains in Red Hat Virtualization for storing virtual machine disks and installation media.

Storage Domains

A storage domain is a repository for virtual machine disk images used for system disks, data, or installation media. There are three types of storage domains (data, iso, and export), but only data domains are needed. Although still available, the iso and export storage domains have been deprecated.

A data domain stores the disk images that represent the virtual hard drives or other storage for virtual machines. These disk images can contain the operating system of the virtual machine or be purely used for data. ISO disk images, used to install virtual machine operating systems and applications, can be uploaded to a data domain. When creating a new virtual machine, an ISO disk image in the data storage domain can be attached to the virtual machine as if was inserted into a CD/DVD drive.

A storage domain can use one of a number of different storage technologies to provide its back end storage:

Red Hat Gluster Storage native client (GlusterFS)
Fiber Channel Protocol (FCP)
Internet Small Computer System Interface (iSCSI)
Network File System (NFS)
Other POSIX-compliant file systems
Local storage attached directly to a virtualization host. The host must be in a data center and cluster containing no other hosts.

For NFS-based storage domains, all virtual disks, templates, and snapshots are stored as files. For block-oriented storage, such as iSCSI and FCP, Red Hat Virtualization uses Logical Volume Management (LVM) to organize the block storage as a volume group, with individual virtual disks, images, and snapshots managed internally as logical volumes.

For a RHV data center to be considered active, it must have at least one cluster containing at least one host with a status of Up. Additionally, a data domain must exist with the active cluster host able to access the data domain's storage. These requirements must be met for a RHV self-hosted engine installation to succeed.

Your RHV self-hosted engine classroom environment contains:

The Default data center contains the Default cluster.
Four RHV hosts (hosta, hostb, hostc, and hostd) belong to the Default cluster and have a status of Up.
The hosted_storage data domain exists and is backed by an NFS share available on utility.lab.example.com. The hosted_storage data domain has a status of active. The initial data domain can be any of the listed storage types. Using NFS is a classroom convenience.

Preparing NFS Exports for Storage Domains

NFS exports, for use as NFS-based storage domains, must be prepared for use with Red Hat Virtualization.

A file system of sufficient size for the storage domain is exported from the NFS server.
The NFS server exports the file system in read-write mode to all Red Hat Virtualization hosts in the cluster. Configure the export in either /etc/exports or a file ending with .exports in /etc/exports.d/ (for example, /etc/exports.d/rhv.exports).
The top-level directory on the exported file system must be owned by user vdsm (UID 36) and by group kvm (GID 36). The directory permissions are set so that user vdsm has read-write-execute access and the kvm group and all other users have read-execute access (octal permissions 0755).
Ensure that nfs-server.service is running and enabled.
If a firewall is in use, verify that all Red Hat Virtualization hosts are allowed access to the NFS share.

Important

The NFS server must not be one of the physical Red Hat Virtualization hosts. The NFS server can be a single point of failure for any storage domains using it, the cluster, and the virtual machines using those storage domains. Ideally, the NFS server should be made resilient and highly available.

The hosted_storage Data Domain

This section shows details of the rebuilt hosted_storage data domain as viewed in the RHV-M Administration Portal.

From the Administration Portal, navigate to the Storage menu and select Domains. The hosted_storage data domain should exist. Details are viewed by right-clicking the hosted_storage link and selecting Manage Domain.

Figure 2.10: Details of the hosted_storage Data Domain.

Data Center: The name of the data center associated with the storage domain. The classroom environment uses the Default data center.
Name: The name of the storage domain. A RHV self-hosted engine installation defaults to creating a data storage domain named hosted_engine. The classroom environment uses this default.
Domain Function: This can be Data, ISO, or Export. An active Data domain needs to exist before ISO and Export appear as options. The ISO and Export functions are deprecated. The hosted_engine storage domain is a data domain.
Storage Type: Available options are NFS, POSIX compliant FS, GlusterFS, iSCSI, and Fibre Channel. The classroom environment uses the NFS storage type.
Host to Use: This can be any active host associated with the selected data center. If this menu is blank, then no hosts are associated with the selected data center or the hosts are not active. For example, the hosts may be in maintenance mode.
Export Path: The information displayed below Host to Use will vary based on the selected storage type. For NFS, export path expects the name of the NFS server and the path to the share. The classroom environment uses utility.lab.example.com:/exports/hosted_engine for the export path.

Uploading ISO Files to a Data Domain

Upload an ISO file if you plan to perform either manual or automated installations of virtual machines. When a network server, such as HTTP or FTP, shares your installation media, uploading a boot ISO can be used as an alternative to uploading a DVD ISO.

Uploading ISO Images with the Administration Portal

Start by downloading one or more ISO files to the machine used to access the RHV Administration Portal. From the Administration Portal, navigate to Storage in the menu and select Disks. The Upload button start an upload, opening a dialog to locate the ISO file on the local system and select it.

For ISO files, the Alias and Description fields default to the name of the ISO file. Use the Data Center and Storage Domain fields to specify the destination for the upload. Use the Disk Profile and Host to Use fields to specify how it should be uploaded, and which will perform the task. Different disk profiles can be created to specify storage quality of service levels.

To upload, you must be able to connect to the ovirt-imageio-proxy. Use the Test Connection button to test that connection. A green success box indicates that the upload can succeed.

Figure 2.11: Upload Image Screen with Successful Connection Test.

If the Test Connection button returns an orange warning box, click the ovirt-engine certificate link.

Figure 2.12: The ovirt-engine Certificate Needs to be Downloaded.

In the Downloading Certificate window, check the box next to Trust this CA to identify websites and then click the OK button. At this point, clicking the Test Connection button returns a green success box.

Figure 2.13: Download the ovirt-engine Certificate and Trust It to Identify Websites.

References

Further information is available in the Storage chapter of the Administration Guide for Red Hat Virtualization; at https://access.redhat.com/documentation/en-us/red_hat_virtualization/4.3/html-single/administration_guide/index#chap-Storage

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Revision: rh318-4.3-c05018e