Tag Archives: ESXi

What’s .NEXT 2016 – Metro Availability Witness

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In 2014, Nutanix introduced Metro Availability which allows Virtual Machines to have mobility between sites as well as to provide failover in the event of a site failure.

The goal of the Metro Availability (MA) Witness is to automate failovers in case of inter-site network failures or site failures. By the virtue of running the Witness in a different location than the two Metro Sites, it provides the ‘outside’ view that can determine whether a site is actually down or whether the network connection between the two sites is down, avoiding a split-brain scenario that can occur without an external Witness.

The main functions of a Witness include:

  • Making failover decision in the event of site or inter-site network failure
  • Avoiding split brain where the same container is active on both sites
  • Design to handle situations where a single storage or network domain fails

For example, in the case of a Metro Availability (MA) relationship between clusters, a Witness residing in a separate failure domain (e.g.: 3rd site) decides which site should be activated when a split brain occurs due to a WAN failure, or in the situation where a site goes down. For that reason, it is a requirement that there are independent network connections for inter-site connectivity *and* for connections to the witness.

How Metro works without a Witness:

In the event of the primary site failure (the site where the Metro container is currently active) or the links between the sites going offline, the Nutanix administrator is required to manually Disable Metro Availability and Promote the Container to Active on the site where VMs are desired to be ran. This is a quick and simple process, but it is not automated which may impact the Recovery Time Objective (RTO).

In case of a communication failure with the secondary site (either due to the site going down or the network link between the sites going down), the Nutanix administrator can configure the system in two ways:

  • Automatic: the system will automatically disable Metro Availability on the container on the primary site after a short pause if the secondary site connection doesn’t recover within that time
  • Manual: wait for the administrator to manually take action

MetroNoWitness

How Metro Availability (MA) works with the witness:

With the new Witness capability, the process of disabling Metro Availability and Promoting the Container in case of a site outage or a network failure is fully automated which ensures the fastest possible RTO.  The Witness functionality is only used in case of a failure, meaning a Witness failure itself will not affect VMs running on either site.

MetroWithWitness

Failure Scenarios Addressed by MA Witness.

There are a number of scenarios which can occur and Metro Availability responds differently depending on if MA is configured in “Witness mode”, “Automatic Resume mode” or in “Manual mode”.

The following table details the scenarios and the behaviour based on the configuration of Metro Availability.

MetroFailureScenarios3

In all cases except a failure at both Site 1 and Site 2, the MA Witness automatically handles the situation and ensures the fastest possible RTO.

The following videos show how each of the above scenarios function.

Deployment of the Metro Availability (MA) Witness:

The Witness capability is deployed as a stand-alone Virtual Machine, that can be imported on any hypervisor in a separate failure domain, typically a 3rd site.  This VM can run on non-Nutanix hardware.  This site is expected to have dedicated network connections to Site 1 and Site 2 to avoid a single point of failure.

As a result, MA Witness is quick and easy to deploy, resulting in lower complexity and risk compared to other solutions on the market.

Summary:

The Nutanix Metro Witness completes the Nutanix Metro Availability functionality by providing completely automatic failover in case of site or networking failures.

Related .NEXT 2016 Posts

Nutanix Data Protection Capabilities

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There is a lot of misinformation being spread in the HCI space about Nutanix data protection capabilities. One such example (below) was published recently on InfoStore.

Evaluating Data Protection for Hyperconverged Infrastructure

When I see articles like this, It really makes me wonder about the accuracy of content on these type of website as it seems articles are published without so much as a brief fact check from InfoStore.

None the less, I am writing this post to confirm what Data Protection Capabilities Nutanix provides.

  • Native In-Built Data protection

Prior to my joining Nutanix in mid-2013, Nutanix already provided a Hypervisor agnostic Integrated backup and disaster recovery solution with centralised consumer- grade management through our PRISM GUI which is HTML 5 based.

The built in capabilties are flexible and VM-centric policies to protect virtualized applications with different RPOs and RTOs with or without application consistency.

The solution also supports Local, remote, and cloud-based backups, and synchronous and asynchronous replication-based disaster recovery solutions.

Currently supported cloud targets include AWS and Azure as shown below.

CloudBackup

The below video which shows in real time how to create Application consistent snapshots from the Nutanix PRISM GUI.

Nutanix can also perform One to One, One to Many and Many to One replication of application consistent snapshots to onsite or offsite Nutanix clusters as well as Cloud providers (AWS/Azure), ensuring choice and flexibility for customers.

Nutanix native data protection can also replicate between and recover VMs to clusters of different hypervisors.

  • CommVault Intellisnap Integration

Nutanix also provides integration with Commvault Intellisnap which allows existing Commvault customers to continue leveraging their investment in the market leading data protection product and to take advantage of other features where required.

The below shows how agentless backups of Virtual Machines is supported with Acropolis Hypervisor (AHV). Note: Commvault is also fully supported with Hyper-V and ESXi.

By Commvault directly calling the Nutanix Distributed Storage Fabric (NDSF) it ensures snapshots are taken quickly and efficiently without the dependancy on a hypervisor.

  • Hypervisor specific support such as VMware API Data Protection (VADP)

Nutanix also supports solutions which leverage VADP, allowing customers with existing investment in products such as Veeam & Netbackup to continue with their existing strategy until such time as they want to migrate to Nutanix native data protection or solutions such as Commvault.

  • In-Guest Agents

Nutanix supports the use of In-Guest agents which are typically very inefficient with centralised SAN/NAS storage but due to data locality and NDSF being a truly distributed platform, In-Guest Incremental forever backups perform extremely well on Nutanix as the traditional choke points such as Network, Storage Controllers & RAID packs have been eliminated.

Summary:

As one size does not fit all in the world of I.T, Nutanix provides customers choice to meet a wide range of market segments and requirements with strong native data protection capabilities as well as 3rd party integration.

Nutanix Implementation of Data Avoidance & Reduction Technologies

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While its not news that Nutanix Distributed Storage Fabric (NDSF) supports numerous data avoidance & reduction technologies, what is less well known is how these technologies can be enabled/disabled and used.

Before we begin, let me cover off what technologies NDSF offers:

Data Avoidance:

  • VAAI-NAS Fast File Clone (for ESXi)
  • View Composer for Array Integration (VCAI) for Horizon View
  • Native NDSF Clones (ESXi, Hyper-V and AHV)
  • ODX Copy Offload (Hyper-V)
  • Crash and Application Consistent snapshots (ESXi, Hyper-V and AHV)

Data Reduction:

  • Compression (In-Line and Post-Process)
  • Deduplication (Fingerprint on Write/In-Line for Performance Tier and/or Capacity Tier)
  • Erasure Coding (EC-X)

Data avoidance is designed to prevent the creation of unnecessary data which removes the requirement to leverage data reduction technologies. This means less work for the storage layer which results in more available front end IO to service the virtual machines.

An example of data avoidance is using VCAI with Horizon View to create Linked Clones near instantly which not only reduces space but ensures faster deployment and recompose activities with greatly reduced impact to the environment.

Data avoidance is greatly underrated in my opinion, as it results in lower compression/deduplication ratios, because there is no additional data to dedupe or compress. If Nutanix turned off these data avoidance technologies, it would result in HIGHER compression and dedupe ratios, which sounds great on a marketing slide or in a tweet, but in reality, avoiding work for the storage is a much better way to do things.

Some vendors report data avoidance such as snapshots in deduplication ratios, and this in my opinion is very misleading and designed to artifically inflate dedupe ratios for competitive purposes. For more information see: Deduplication ratios – What should be included in the reported ratio?

Data Reduction is still a valuable option to have but in my opinion its overrated. The reason I think its overrated is data reduction does not always work well. It greatly depends on your data type if you will see a good data reduction ratio or not, AND if the overheads (of which there is always an overhead) are worth it.

Let’s now focus on the NDSF implementation of Data Reduction technologies.

Compression:

Compression can be configured on new or existing containers and be set to In-Line or Post-Process. For post process, enter a “Delay” value e.g.: 60 to delay compression for 1 Hour, or 3600 for 1 day.

Compression

Compression can be reconfigured at any time, without the requirement to relocate VMs or reformat the storage. For data which is already compressed it will be uncompressed as part of a low priority background task (known as Curator). This ensures there is low/no impact of changing Compression settings, ensuring maximum flexibility for customers.

Because compression is configured per container, you can have VMs or even Virtual Disks running compression alongside VMs or Virtual Disks not running compression within the same NDSF cluster. This helps eliminate silos and ensures mixed workloads with different data types/profiles can co-exist efficiently.

Deduplication:

As with Compression, Deduplication can be configured on new or existing containers and be set to dedupe for the performance tier (SSD) and optionally for the Capacity (HDD) Tier. This means data reduction can be maximised for either or both tiers depending on customer requirements.

dedupeconfig

Again the same as Compression, Dedupe can be reconfigured at any time, without the requirement to relocate VMs or reformat the storage. For data which is already deduped the same low priority background task (Curator) rehydrates the data again ensuring there is low/no impact of changing dedupe settings and ensuring maximum flexibility for customers.

Because dedupe is configured per container, you can have VMs or even Virtual Disks running dedupe alongside VMs or Virtual Disks not running dedupe within the same NDSF cluster. Deduplication is also complimentary to Compression, meaning both can be ran at the same time to maximise data reduction and further eliminate silos ensuring mixed workloads can co-exist efficiently.

Erasure Coding (EC-X):

As with Compression & Dedupe, EC-X is enabled on a per container basis and is complimentary to both Compression and Dedupe. EC-X is a post-process only form of data reduction designed to work on Write cold data (meaning data which is not changing).

EC-X applies to data across the Performance Tier (SSD) and the Capacity Tier (SATA) which means the effective SSD capacity is increased, which means more data can be serviced by SSD, thus increasing performance.

ecxonoff

As previously discussed, NDSF supports different containers using different combinations of data reduction all within the same NDSF cluster to maximise efficiencies and eliminate unnecessary silos.

Summary:

Nutanix provides multiple technologies to minimise the data being stored on the distributed storage fabric while giving customers the flexibility to enable/disable and tune data reduction settings to suit different data profiles all within the same NDSF cluster.

Remember, “one size does not fit all” so it is importaint for the storage layer to be able treat your workloads differently based on their individual requirements.

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