Virtualised Disaster Recovery

The Old Way

The world is embracing Virtualisation – and so it should.  Hardware technology is becoming more powerful and we have had an era of excessive power usage.  The world is running out of resources and we need to use the power of the new hardware to use less of it.  Running more on less means we consume less.  We need less equipment to do more, and therefore consume less energy producing it and running it.

We now have Hypervisor software from companies like VMWare and Citrix that allow us to run multiple hosts on powerful server and SAN hardware.  Data centres still need to have a host per application so that  software titles do not conflict, as well as needing set amounts of hardware resource (Disk space, RAM, Processing power) as set by the software creator’s set requirements, in order to be fully supported.  An Enterprise anti-virus server application cannot run on the same host as another title, from another vendor, or it won’t be supported.  It’s not to say that two titles wont work together – they just don’t get built that way.

Until recently (approx. 3 years ago), many companies ran their infrastructure designs using physical server farms and large SAN storage arrays, to accommodate each of the varying software titles that are required to complete the application suite.


With Hypervisor VMWare or Citrix based platforms the number of hosts is reduced, therefore making an energy and cost saving on host server hardware.


This is achievable due to more powerful single servers being available to the market.  More powerful processing power, means they can each do more computing.

The above, simple illustrations, show a pattern where server farms have reduced in size, storage has arguably not.  Storage has been increasing in order to accommodate the expanding virtual farms – previously, the host servers ran the OS on their own internal disk drives.  As the host server runs multiple guest Operating Systems, it’s storage requirement grows.  Effectively we have removed the storage from the host server and we need it in the Storage device.  It does appear that although the server stack has shrunk, without storage technology improving, the SAN Storage stack grows.


This makes little or no energy or cost saving.  Storage products tend to use more power and cost more.

The New Way

GreenBytes HA-3000 High Availability (HA) Inline Deduplicating iSCSI SAN

New iSCSI SAN products like the GreenBytes HA-3000 High Availability (HA) Inline Deduplicating iSCSI SAN, allow less storage through technology improvements like inline deduplication and compression, where copies of each file are trimmed down to a simple pointer.  This creates a smart storage device that stores a single copy of an 100GB OS VM and 1000x 10GB copies of it all on the same device.


Now we are starting to see a picture of real power, heat, cooling and hardware cost savings.  This technology allows a 26TB SAN appliance to host multiple instances of VMs, negating the need for large disk arrays.  See The Virtualisation Journey previous post on this technology.



Backup, Restore and Disaster Recovery

So far, we have roughly explored the transition in infrastructure design and the problems facing the IT industry in making reductions in power and cost.  The problems are not simply solved by adding storage.  We have briefly explored the new storage appliance from GreenBytes that can drastically reduce the amount of storage hardware using smart compression and deduplication technology.  However, storage is always a growing entity for a growing business.

Each time a disk is added, the question of what to do should it fail arises.  Failure and subsequent loss of data is not the only pain that is felt in a disaster.  There is downtime to the end user, cost of recovery of the data in labour and of course, a loss to the business.

There is an entire industry around Backup and Disaster Recovery (DR) and ways of seamlessly resolving failures of hardware and software running in a virtual environment, that minimize  disruption to a business.  Most have evolved from the multiple hosts with 1 application per host environments, as we saw at the start of this article.  In this scenario, the important data was stored on the SAN – The OS on the host could be quickly rebuilt from an image, therefore backing up the SAN stored data took priority – in most installations this would be achieved using a duplicate of the SAN and a fast and expensive data connection between the local and a remote site.


This is still true today, of virtually all medium to large IT infrastructure designs.  There is too much data to go to tape, it takes too long to write to and read back in – those days are long gone for most installations.

Virtualised Backup and DR

As environments have moved into the virtualised field, where the SAN stores the actual OS as well as the data, Backup technology has centred around the backing up of the SAN.  This has meant that engineering teams have split into those who look after the SAN and those who look after the hosts.

The SAN is backed up to it’s remote SAN partner and this task is performed by Storage Engineers.  They perform LUN to LUN or Volume to Volume backups which is controlled within the storage device software. 

The Hypervisor engineer, when experiencing a failure can shuffle his/her VM around through technologies such as VMotion while it runs, on the fly, but to do this on a large scale requires manpower.  The VM and VMDK can be moved between hosts but this can be labour intensive.

Introducing Zerto

“Business Continuity and Disaster Recovery for the Cloud Era”

Zerto is a hypervisor-based replication and recovery technology that integrates with VMware vSphere and is managed from within vCenter. Zerto software performs continuous, near-syncronous replication at the Hypervisor level rather than at the Storage Level.

This gives control back to the Virtual host engineer where he can replicate and recover whole virtual environments, using continuous replication with block-level application-consistent data protection across both the host and the storage.

Zerto replication separates the application from its physical constructs at the data-protection level. It works on any storage device containing a datastore within your virtual datacenter and works with NetApp, EMC or any other storage vendor’s appliance.

To enable full application recovery, Zerto has developed Virtual Protection Groups. VPGs are a collection of VMs and their related VMDKs, which have dependencies and must be recovered with write-order fidelity. Zerto VPGs ensure applications are replicated and recovered with consistency, regardless of the underlying infrastructure.

Single click protection

Any VM in vSphere vCenter can be protected from a single click without any extra configuration. There is no client or agent software required to be installed on the guest OS. Zerto protects at the VM and VMDK level. This allows the Virtual Host engineer to protect the virtualised environment without storage constraints.

Tasks available include:

  • Replicate single or multiple VMs
  • Create VPGs – Virtual Protection Groups with write-order fidelity
  • Protect multiple VMDKs connected to the same VM
  • Support replication of RDM devices to a remote VMDK or RDM
  • Use an intuitive GUI embedded in vSphere vCenter
  • View and manage local and remote sites from the same vCenter clientRemote installation, takes under an hour
  • Seamless support for vMotion, DRS and HA while replicating
  • WAN optimization – built-in WAN compression and application policies
  • Replication, Testing, CDP, Reporting and Migration

Zerto removes the need to use multiple solutions for Disaster Recovery. All tasks are accomplished using built–in, easy to follow wizards within the tool.

These include:

  • Failover one or more VPGs, including automatic reverse replication
  • Recover to a historic point-in-time with journal-based CDP
  • Recover volumes instantly, in read-write format
  • Test failover, including full remote recovery in a sandboxed zone
  • Migrate workloads to a remote data center
  • Get comprehensive reporting on all system-wide activities

Cloud-Ready Disaster Recovery

Disaster recovery to the cloud is considered by many enterprises as a natural first step in the journey to the cloud, being an effective alternative to in-house DR sites.

Zerto’s technology fits perfectly with the specific needs of both enterprises and cloud providers.

  • Replication from any storage to any storage
  • Management API
  • Built-in WAN optimization
  • Native multi-tenancy support
  • Software only, highly scalable
  • Tier-one protection level

Supported Environments

  • ESX/ESXi 4 vSphere 5 support scheduled for 1/2012
  • Storage: SAN, NAS, FC, iSCSI, DAS, and all external and internal storage supported by VMware, including replication between different storage types
  • Volumes: VMFS, Virtual RDM, Physical RDM, including replication between volume types
  • Guest OS: all OS supported by VMware
  • Virtualization Features: vAPP, HA, DRS, vMotion, Storage vMotion.

Get in touch here, call 08452990793 for a free trial or check out for more information

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