vSAN Management Cluster
vSAN Management Cluster
HyperConverged Infrastructure for Management Clusters
A VMware vSphere® management cluster is a dedicated group of hosts reserved for running virtual machines that provide management services to infrastructure environments. These services might include, but are not limited to, directory services, DNS, DHCP, VMware vCenter Server™, VMware Aria® Operations™, and VMware Site Recovery Manager™.
A management cluster separated from other vSphere clusters helps guarantee sufficient compute resources are always available to these critical infrastructure services for improved reliability and performance. In the event of a site failure and subsequent recovery, it is typically easier and faster to bring the foundational infrastructure services back online since they are located in a smaller, dedicated cluster.
In addition to dedicating compute resources, separate storage should be provided to the management cluster for the same reasons we dedicate compute resources. Dedicated storage resources help ensure high levels of performance and availability. They also make it easier to architect proper data protection and disaster recovery for the workloads in the management cluster.
Compute and storage resources for a management cluster should be simple to implement, cost-effective, and provide the performance and availability features necessary to protect critical infrastructure workloads. vSphere and VMware vSAN™ provide the HyperConverged Infrastructure (HCI) best suited to meet these requirements.
Why vSAN for a Management Cluster?
vSAN is natively integrated with vSphere and it is configured with just a few mouse clicks. Since disks internal to the vSphere hosts are used to create a vSAN datastore, there is no dependency on external shared storage. Virtual machines can be assigned specific storage policies based on the needs of the management application. Management workloads benefit from dependable storage with predictable performance characteristics.
Virtual machine-centric storage policies can be created and assigned for various workload types. Policies are based on the available services provided by the storage platform. These policies can be modified and reassigned, as needed, with no downtime.
A dedicated HCI with vSphere and vSAN help ensure predictable performance and availability of management applications and services. Running management workloads in a separate compute and storage facilitates more flexible maintenance schedules. If maintenance is required in the management cluster, there is typically no need to coordinate planned downtime across all of the business applications running on other storage platforms.
vSAN includes a health service, which automatically monitors and alerts on items such as overall disk health, hardware compatibility list (HCL) compliance, network connectivity issues, and utilization. This feature makes it easy for administrators to understand the overall health of the cSAN cluster at a glance.
vSAN with vSphere Availability
The use of local disks without vSAN introduces risk to application uptime. For example, only one copy of a virtual machine’s files is stored on a local disk. If that disk fails, the virtual machine files must be restored from backup media, which is time-consuming and, in some cases, unreliable. It is possible to create a second copy of virtual machine files on another disk, but the process is not automatic and must be performed frequently to minimize data loss. The recovery of a second copy would also be a manual process further increasing risk and recovery time.
vSAN addresses these challenges by aggregating local disks into a shared datastore distributed across hosts in the cluster. vSAN features a storage policy rule called “Primary Level of Failures to Tolerate” or “PFTT”, which defines the number of copies of a virtual machine’s files to distribute across the physical nodes in the cluster. The formula for determining the minimum number of hosts required to support a PFTT rule is 2n+1. For example, five hosts are required for PFTT=2. Services such as VMware vSphere vMotion®, VMware vSphere High Availability™ (vSphere HA), and VMware vSphere Fault Tolerance™ ( vSphere FT) work seamlessly with vSAN to protect management workloads.
vSphere Replication™ is included with vSphere Essentials Plus Kit and higher editions of vSphere. It provides per-VM replication with RPOs as low as five minutes. After the initial replication is completed, only changed data is replicated to minimize network bandwidth consumption. vSphere Replication can replicate virtual machines locally (within the same cluster) and to locations such as another cluster at the same site or a remote site. Virtual machine recovery is fast and easily performed with just a few mouse clicks. vSphere Replication helps minimize unplanned downtime for essential management workloads.
vSAN Performance
vSAN is uniquely embedded in the vSphere hypervisor kernel and sits directly in the I/O data path. vSAN is able to deliver the highest levels of performance without taxing the CPU or consuming high amounts of memory resources, as compared to other storage virtual machine appliances that run separately on top of the hypervisor. All-flash configurations deliver high levels of IOPS and throughput with predictable low latency. A combination of magnetic and solid-state disks can also be used to enable flash-accelerated hybrid architectures.
With vSAN, it is possible to apply policies with precision. For example, database servers are commonly deployed with the guest OS on one virtual disk and databases on other virtual disks. A storage policy with multiple stripes could be assigned specifically to the virtual disks containing databases to help guarantee read performance.
Clarity with vRealize Operations Manager
vRealize Operations Manager features predictive analytics and smart alerts to help ensure optimum performance and availability of applications and infrastructures. vRealize Operations Manager includes vSAN dashboards enabling administrators to monitor several factors such as throughput, latency, capacity, and cache hits across multiple clusters. If there is an issue in the environment, vRealize Operations makes it easy to review symptoms and it provides recommendations for remediation.
Reduced Cost and Complexity
vSAN simplifies managing and automating storage for management workloads by eliminating traditional, purpose-built storage systems and by letting IT use familiar vSphere Web Client tools rather than proprietary storage management interfaces. vSAN integrates storage policies into the virtual machine creation workflow, ensuring each workload has the type of storage it needs. vSAN does not require the installation of virtual storage appliances and you can enable vSAN with just a few clicks.
vSAN is a distributed architecture that allows for elastic, non-disruptive scaling. Capacity and performance can be scaled at the same time by adding a new host to the cluster (scale out) or capacity and performance can be scaled independently by adding new drives to existing hosts (scale up). This “grow-as-you-go” model provides predictable, linear scaling with affordable investments spread out over time.
Summary
vSAN and vSphere are the ideal HCI platform for running management workloads where predictable performance and high availability are strict requirements. Virtual machines running important applications such as directory services, DNS, and vCenter Server do not have to compete for compute and storage resources shared by business workloads. Virtual machine-centric storage policies can be created, assigned, and modified, as needs change in the environment without incurring downtime. Maintenance windows are easier to schedule and there are features such as vSphere HA and vSphere Replication to enable rapid recovery from unplanned downtime. vSAN health monitoring is included and, optionally, vRealize Operations Manager provides multiple vSAN dashboards for proactive alerting, heat maps, device and cluster insights, and streamlined issue resolution.