Chapter 3. Support requirements

Review this section to ensure that your planned deployment meets the requirements for support by Red Hat.

3.1. Operating system

Red Hat Hyperconverged Infrastructure for Virtualization (RHHI for Virtualization) uses Red Hat Virtualization Host 4.4 as a base for all other configuration. Red Hat Enterprise Linux hosts are not supported.

See Requirements in the Red Hat Virtualization Planning and Prerequisites Guide for details on requirements of Red Hat Virtualization.

3.2. Physical machines

Red Hat Hyperconverged Infrastructure for Virtualization (RHHI for Virtualization) requires at least 3 physical machines. Scaling to 6, 9, or 12 physical machines is also supported; see Scaling for more detailed requirements.

Each physical machine must have the following capabilities:

  • at least 2 NICs (Network Interface Controllers) per physical machine, for separation of data and management traffic (see Section 3.5, “Networking” for details)
  • for small deployments:

    • at least 12 cores
    • at least 64GB RAM
    • at most 48TB storage
  • for medium deployments:

    • at least 12 cores
    • at least 128GB RAM
    • at most 64TB storage
  • for large deployments:

    • at least 16 cores
    • at least 256GB RAM
    • at most 80TB storage

3.3. Virtual machines

The number of virtual machines that you are able to run on your hyperconverged deployment depends greatly on what those virtual machines do, and what load they are under. Test your workload’s CPU, memory, and throughput requirements and provision your hyperconverged environment accordingly.

See Virtualization limits for Red Hat Virtualization for information about maximum numbers of virtual machines and virtual CPUs, and use the RHHI for Virtualization Sizing Tool for assistance planning your deployment.

3.4. Hosted Engine virtual machine

The Hosted Engine virtual machine requires at least the following:

  • 1 dual core CPU (1 quad core or multiple dual core CPUs recommended)
  • 4GB RAM that is not shared with other processes (16GB recommended)
  • 25GB of local, writable disk space (50GB recommended)
  • 1 NIC with at least 1Gbps bandwidth

For more information, see Requirements in the Red Hat Virtualization 4.4 Planning and Prerequisites Guide.

3.5. Networking

Fully-qualified domain names that are forward and reverse resolvable by DNS are required for all hyperconverged hosts and for the Hosted Engine virtual machine.

If external DNS is not available, for example in an isolated environment, ensure that the /etc/hosts file on each node contains the front and back end addresses of all hosts and the Hosted Engine node.

IPv6 is supported in IPv6-only environments (including DNS and gateway addresses). Environments with both IPv4 and IPv6 addresses are not supported.

Red Hat recommends usage of separate networks: a front-end management network for virtual machine traffic and a back-end storage network for gluster traffic and virtual machine migration.

Figure 3.1. Network diagram

Diagram of separate networks and their purposes in RHHI for Virtualization

Red Hat recommends each node to have two Ethernet ports, one for each network. This ensures optimal performance. For high availability, place each network on a separate network switch. For improved fault tolerance, provide a separate power supply for each switch.

Front-end management network
  • Used by Red Hat Virtualization and virtual machines.
  • Requires at least one 1Gbps Ethernet connection.
  • IP addresses assigned to this network must be on the same subnet as each other, and on a different subnet to the back-end storage network.
  • IP addresses on this network can be selected by the administrator.
Back-end storage network
  • Used by storage and migration traffic between hyperconverged nodes.
  • Requires at least one 10Gbps Ethernet connection.
  • Requires maximum latency of 5 milliseconds between peers.

Network fencing devices that use Intelligent Platform Management Interfaces (IPMI) require a separate network.

If you want to use DHCP network configuration for the Hosted Engine virtual machine, then you must have a DHCP server configured prior to configuring Red Hat Hyperconverged Infrastructure for Virtualization.

If you want to configure disaster recovery by using geo-replication to store copies of data, ensure that you configure a reliable time source.

Before you begin the deployment process, determine the following details:

  • IP address for a gateway to the hyperconverged host. This address must respond to ping requests.
  • IP address of the front-end management network.
  • Fully-qualified domain name (FQDN) for the Hosted Engine virtual machine.
  • MAC address that resolves to the static FQDN and IP address of the Hosted Engine.

3.6. Storage

A hyperconverged host stores configuration, logs and kernel dumps, and uses its storage as swap space. This section lists the minimum directory sizes for hyperconverged hosts. Red Hat recommends using the default allocations, which use more storage space than these minimums.

  • / (root) - 6GB
  • /home - 1GB
  • /tmp - 1GB
  • /boot - 1GB
  • /var - 15GB
  • /var/crash - 10GB
  • /var/log - 8GB

    Important

    Red Hat recommends increasing the size of /var/log to at least 15GB to provide sufficient space for the additional logging requirements of Red Hat Gluster Storage.

    Follow the instructions in Growing a logical volume using the Web Console to increase the size of this partition after installing the operating system.

  • /var/log/audit - 2GB
  • swap - 1GB (see Recommended swap size for details)
  • Anaconda reserves 20% of the thin pool size within the volume group for future metadata expansion. This is to prevent an out-of-the-box configuration from running out of space under normal usage conditions. Overprovisioning of thin pools during installation is also not supported.
  • Minimum Total - 64GB

3.6.1. Disks

Red Hat recommends Solid State Disks (SSDs) for best performance. If you use Hard Drive Disks (HDDs), you should also configure a smaller, faster SSD as an LVM cache volume. The cache device must use the same block size as the other volumes.

Do not host the bricks of a Gluster volume across disks that have different block sizes. Ensure that you verify the block size of any VDO devices used to host bricks before creating a volume, as the default block size for a VDO device changed from 512 bytes in version 1.6 to 4 KB in version 1.7. Check the block size (in bytes) of a disk by running the following command:

# blockdev --getss <disk_path>

3.6.2. RAID

RAID5 and RAID6 configurations are supported. However, RAID configuration limits depend on the technology in use.

  • SAS/SATA 7k disks are supported with RAID6 (at most 10+2)
  • SAS 10k and 15k disks are supported with the following:

    • RAID5 (at most 7+1)
    • RAID6 (at most 10+2)

RAID cards must use flash backed write cache.

Red Hat further recommends providing at least one hot spare drive local to each server.

3.6.3. JBOD

As of Red Hat Hyperconverged Infrastructure for Virtualization 1.6, JBOD configurations are fully supported and no longer require architecture review.

3.6.4. Logical volumes

The logical volumes that comprise the engine gluster volume must be thick provisioned. This protects the Hosted Engine from out of space conditions, disruptive volume configuration changes, I/O overhead, and migration activity.

The logical volumes that comprise the vmstore and optional data gluster volumes must be thin provisioned. This allows greater flexibility in underlying volume configuration.

If your thin provisioned volumes are on Hard Drive Disks (HDDs), configure a smaller, faster Solid State Disk (SSD) as an lvmcache for improved performance. The cache device must use the same block size as the other volumes.

3.6.5. Red Hat Gluster Storage volumes

Red Hat Hyperconverged Infrastructure for Virtualization is expected to have 3–4 Red Hat Gluster Storage volumes.

  • 1 engine volume for the Hosted Engine
  • 1 vmstore volume for virtual machine operating system disk images
  • 1 data volume for other virtual machine disk images
  • 1 shared_storage volume for geo-replication metadata

Separate vmstore and data volumes are recommended to minimize backup storage requirements. Storing virtual machine data separate from operating system images means that only the data volume needs to be backed up when storage space is at a premium, since operating system images on the vmstore volume can be more easily rebuilt.

3.6.6. Volume types

Red Hat Hyperconverged Infrastructure for Virtualization (RHHI for Virtualization) supports only the following volume types at deployment time:

You can create distributed replicate or distributed arbitrated replicate volumes during the deployment of Red Hat Hyperconverged Infrastructure for Virtualization using Ansible playbooks as mentioned in the guide Automating RHHI for Virtualization deployment.

Note that arbiter bricks store only file names, structure, and metadata. This means that a three-way arbitrated replicated volume requires about 75% of the storage space that a three-way replicated volume would require to achieve the same level of consistency. However, because the arbiter brick stores only metadata, a three-way arbitrated replicated volume only provides the availability of a two-way replicated volume.

For more information on laying out arbitrated replicated volumes, see Creating multiple arbitrated replicated volumes across fewer total nodes in the Red Hat Gluster Storage Administration Guide.

3.7. Disk encryption

Disk encryption is supported as of Red Hat Hyperconverged Infrastructure for Virtualization 1.8.

The supported method is Network-Bound Disk Encryption (NBDE), which uses a key server to provide decryption keys to encrypted clients at boot time, avoiding the need to enter the decryption password manually.

NBDE support requires at least 1 additional server (physical or virtual) to act as the NBDE key server. For fault tolerance, Red Hat recommends 2 NBDE key servers.

NBDE key servers must not be part of the Red Hat Hyperconverged Infrastructure for Virtualization cluster.

NBDE key servers can use either of the following operating systems:

  • Red Hat Enterprise Linux 7.8 and higher
  • Red Hat Enterprise Linux 8.2 and higher

Disk encryption generally involves a small reduction in performance. Test this configuration thoroughly before putting it into production to ensure that it meets the performance requirements of your use case, particularly if you are using disk encryption with other technology that creates a slight reduction in speed, such as deduplication and compression using Virtual Disk Optimization.

3.8. Virtual Data Optimizer (VDO)

A Virtual Data Optimizer (VDO) layer is supported as of Red Hat Hyperconverged Infrastructure for Virtualization 1.6.

VDO support is limited to new deployments only; do not attempt to add a VDO layer to an existing deployment.

Be aware that the default block size for a VDO device changed from 512 bytes in version 1.6 to 4 KB in version 1.7. Do not host the bricks of a Gluster volume across disks that have different block sizes.

Because reducing data has additional processing costs, enabling compression and deduplication reduces write performance. As a result, VDO is not recommended for performance sensitive workloads. Red Hat strongly recommends that you test and verify that your workload achieves the required level of performance with VDO enabled before deploying VDO in production, especially if you are using it in combination with other technology that reduces performance, such as disk encryption.

3.9. Scaling

The number of nodes you can have in an initial deployment depends on your deployment method.

  • When you use the web console, you can deploy either 1 or 3 hyperconverged nodes.

    In this case, you cannot create a volume that spans more than 3 nodes at creation time; you must create a 3-node volume first and then expand it across more nodes after deployment.

  • When you use Ansible automation, you can deploy up to the maximum of 12 hyperconverged nodes, and span volumes across the required number of nodes at deployment time.

1 node deployments cannot be scaled.

Other deployments can be scaled from a minimum of 3 nodes to 6, 9, or 12 nodes.

You can scale your deployment by adding disks and expanding Gluster volumes. Add disks on new or existing nodes and use them to either create new Gluster volumes or expand existing Gluster volumes.

3.10. Existing Red Hat Gluster Storage configurations

Red Hat Hyperconverged Infrastructure for Virtualization is supported only when deployed as specified in this document. Existing Red Hat Gluster Storage configurations cannot be used in a hyperconverged configuration. If you want to use an existing Red Hat Gluster Storage configuration, refer to the traditional configuration documented in Configuring Red Hat Virtualization with Red Hat Gluster Storage.

3.11. Disaster recovery

Red Hat strongly recommends configuring a disaster recovery solution. For details on configuring geo-replication as a disaster recovery solution, see Maintaining Red Hat Hyperconverged Infrastructure for Virtualization: https://access.redhat.com/documentation/en-us/red_hat_hyperconverged_infrastructure_for_virtualization/1.8/html/maintaining_red_hat_hyperconverged_infrastructure_for_virtualization/config-backup-recovery.

3.11.1. Prerequisites for geo-replication

Be aware of the following requirements and limitations when configuring geo-replication:

Two different managers required
The source and destination volumes for geo-replication must be managed by different instances of Red Hat Virtualization Manager.

3.11.2. Prerequisites for failover and failback configuration

Versions must match between environments
Ensure that the primary and secondary environments have the same version of Red Hat Virtualization Manager, with identical data center compatibility versions, cluster compatibility versions, and PostgreSQL versions.
No virtual machine disks in the hosted engine storage domain
The storage domain used by the hosted engine virtual machine is not failed over, so any virtual machine disks in this storage domain will be lost.
Execute Ansible playbooks manually from a separate master node
Generate and execute Ansible playbooks manually from a separate machine that acts as an Ansible master node.

3.12. Additional requirements for single node deployments

Red Hat Hyperconverged Infrastructure for Virtualization is supported for deployment on a single node provided that all Support Requirements are met, with the following additions and exceptions.

A single node deployment requires a physical machine with:

  • 1 Network Interface Controller
  • at least 12 cores
  • at least 64GB RAM
  • at most 48TB storage

Single node deployments cannot be scaled, and are not highly available.