One of the fast-moving trends in enterprise datacenters today is the move toward software defined storage as part of the overall software defined datacenter (SDDC). Software defined storage has made possible very interesting configurations for resiliency purposes at a single site as well as entire site resiliency. VMware’s vSAN solution is a great example of the tremendous benefits of software defined storage solutions and the agility they provide to organizations looking to lower their total cost of ownership as well as allow resiliency models that allow RPO of near zero. How does VMware vSAN software defined storage provide resiliency to virtual infrastructure? With the resiliency benefits that software defined storage like VMware vSAN, do you still need backups and replication?
How VMware vSAN provides Resiliency
With hyper-converged infrastructure there are impressive resiliencies built into the HCI infrastructure itself. For the purposes of this consideration, we will take a look at VMware vSAN and how it is able to provide data resiliency. VMware vSAN pools together server-attached storage to create a storage solution that is highly resilient and is optimized for production workloads.
VMware vSAN as an example provides distributed RAID and cache mirroring which helps to ensure that data is not lost if a disk, host, network, or other component fails. VMware Virtual SAN aggregates locally attached storage into a shared datastore distributed across hosts in the cluster. A mechanism called “Number of Failures to Tolerate” (FTT) defines how many copies of virtual machine data are made and distributed across physical ESXi nodes in the cluster. The vSAN formula for determining this is 2n+1 where “n” represents the number of failures you want to be able to tolerate.
Another interesting resiliency mechanism that allows VMware vSAN clusters to provide resiliency across sites is the stretched cluster. One half of the stretched cluster is dedicated to withstanding failure of either location. The VMware vSAN stretched cluster requires a witness node virtual machine running vSphere as an appliance. This vSAN witness appliances serves as a “tie-breaker” in situations of “split-brain” network connectivity between the two locations. The VMware vSAN witness appliance is not located within the same site as the stretched cluster so typically it is located in a “DR site” that is in a separate location.
Configuring a vSAN 6.6 Stretched Cluster
Stretched clusters provide synchronous replication between two locations in an “active-active” configuration. An RPO of “zero” can be achieved in the event of losing an entire site. This means we can lose an entire site’s worth of compute, memory, and storage resources and still have resources online and available. By utilizing VMware vSphere “HA” or high availability functionality, the virtual machine is simply restarted in the remaining active site in the event the other site goes down.
VMware vSAN is able to provide the above-mentioned resiliency in stretched clusters by the use of fault domains. In a stretched cluster, each site is a separate fault domain. The stretched cluster requires three fault domains – preferred site, secondary site, and a witness host.
Creating vSAN Fault Domains
Does VMware vSAN Resiliency Eliminate Need for Backups and Replication?
Even with the many powerful features and functionality that software defined storage solutions such as VMware vSAN provide, this is still not a substitute for having backups, replication, and multiple backup copies of data safely stored in case of a disaster. Why is this the case? The resiliency that software defined storage solutions like VMware vSAN provides generally protects against hardware or network failures. However, these are not the only risks to business-critical data. Often end users, or even administrators, and also malware prove to be an even greater threat to your data.
Aside from hardware failure, data can be loss either unintentionally or intentionally due to end user or administrator actions. Ransomware has also proven to be very concerning for your most critical data as it silently encrypts data and often goes undetected until the data is already corrupted. These types of issues are not handled by the built-in resiliency of great software defined storage solutions like VMware vSAN.
Organizations must give due diligence to backups and replication. Even with software defined storage solutions, you still want to follow the “3-2-1” backup rule. Using this methodology, you have at least “3” backups stored on “2” different kinds of medium, and have at least “1” copy stored offsite. Importantly, you can make use of a data protection solution that allows backups of your virtual machines, replicating virtual machines to a separate environment, and also allows creating backup copies stored offsite.
For those really quick restores of files, folders, or even an entire virtual machine, a backup job provides the source files that allow quickly recovering from those types of data loss scenarios. Replicating your virtual machine to a separate “DR” environment also provides additional site resiliency. Even though vSAN stretched clusters allow for built in site resiliency, having the extra peace of mind for mission critical workloads allows you to ensure you mean RTO and RPO objectives for your organization. Finally having an offsite DR copy allows having an extra copy of your backup data stored offsite in another location. This could even be in a cloud repository.
Concluding Thoughts
Virtualization technology has certainly yielded some very powerful software defined solutions in the realm of compute, networking, and storage. VMware vSAN is a great example of one such software defined storage solution that allows you to be agile, flexible, and resilient. However, even though solutions such as VMware vSAN include impressive resiliency abilities, you still need to give due attention to backups, replication, and offsite backup copies. Generally speaking, the resiliency capabilities of modern software defined storage solutions are meant to protect you from data loss resulting in hardware or network failure and not data loss that is a result of accidental or intentional user actions. Data loss as a result of ransomware infection is also a data loss scenario that is not inherently addressed by software defined storage data protection resiliency.
By making good use of modern data protection solutions such as Vembu BDR Suite, you can bolster software defined platform resiliency even further. With Vembu BDR Suite 3.9, you can fully satisfy the 3-2-1 backup methodology with backup to tape. Vembu BDR Suite backups protect software defined workloads so that data can be recovered at the file or folder level, or by rapidly restoring an entire virtual machine using the “Quick VM Recovery” option. With virtual machine replication, Vembu allows you to replicate workloads to separate virtual environments to bolster site resiliency. Offsite DR copies allow you to copy backup data to an offsite server or even to the cloud. No matter how good the resiliency of the underlying platform, never neglect the need to perform good backups. By doing so, your organization can maintain business continuity and recover from any type of data loss.
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