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Disaster recovery planning is something that seems challenging for all businesses. Virtualization in addition to its operational flexibility, and cost reduction benefits, has helped companies improve their DR posture. Virtualization has made it easier to move machines from production to recovery sites, but many of the disaster recovery tools today still function at the storage layer. Legacy technologies like storage array snapshots, and LUN based replication restrict the configuration options of upstream technologies like VMware Storage DRS. If you wanted to replicate a virtual machine you had to replicate the entire LUN is resided on. You weren’t free to leverage Storage DRS for its automated performance balancing features because a VM could be migrated from one LUN mucking up your storage based replication.

Fortunately over the past few years there’s been great advancement in hypervisor based replication technologies. There’s a wealth of competing products vying for customer attention. As always competition drives innovation and value for the consumer. This will be the first of a 4 part blog series that looks at various hypervisor based disaster recovery products. Note this isn’t a review of backup products which is a separate category, we are looking at products specifically designed to assist companies in a disaster scenario.

Before talking about products; however, we should understand their underlying architectures, and how it relates to their storage based predecessors. Like storage based technologies hypervisor based replication technologies currently come in two flavors:

Snap and replicate

Write journaling

These technologies should be very familiar to storage administrators. Write journaling is a newer technology, and the market leader is currently EMC’s Recover Point product. Different storage arrays all have slightly different terms for snap and replicate technologies, but the principals are the same. It’s important to understand this because the technologies will dictate how tightly you can define your recovery time objectives (RTOs) and recovery point objectives (RPOs).

First we will cover snap and replicate technologies. Snap and replicate at the hypervisor level works similarly to its storage counterpart. Instead of taking a snapshot of a storage LUN on a scheduled basis VMware takes a snapshot of the virtual machine’s disks on a scheduled basis. This allows products to copy those disks off of the primary storage media to a secondary location. A nice benefit about using VMware snap and replicate technologies is that you can use completely different types of storage systems on the product and DR systems. You can you and enterprise class SAN in the production datacenter, and internal storage if desired at the disaster recovery location. As long as the storage subsystem is supported by VMware, and has the proper performance characteristics the technology works. Typically a technology called change block tracking keeps track of any data that may change during the backup window.

Write splitting is the second technology we will examine. Like snap and replicate technologies write splitting at the hypervisor level doesn’t require the same storage type at the primary and secondary sites. Write splitting at the hypervisor level is a fairly new technology, but it’s been developed by the same team that developed write splitting at the storage layer. When I evaluate a technology I like to know there’s a history of success from the team that’s created it.

Virtual machine write journaling works differently than storage based write journaling. Instead of having a physical appliance that sits in front of your storage arrays the write splitting occurs inside the ESXi kernel. Because the technology is splitting every write there are some significant technical benefits. As a general rule snap and replicate technologies can in best case scenarios only achieve 15 minutes RTOs and RPOs. White journaling under best case scenarios can deliver RTOs and RPOs from 5 to 10 seconds.

While there is certainly an RTO and RPO benefit to the write journaling technology there are other things to consider. Hero numbers are great for the marketing team, but anyone who’s worked in operations knows what really matters about the product generally isn’t on a spec sheet. All of the products we will talk about work differently, but they all seek to achieve the same result. The supporting infrastructure and associated management costs for all of these products is critical.

Every technology we’re examining works on a management server / replication server architecture. Some of these packages use Windows proxies while other products use Linux based proxies. Consider if you’re planning a massive DR project what if there are dozens of Windows licenses you have to account for, time to patch and manage those virtual machines, etc. If you fall into the scope of PCI you will most likely be required to manage anti-virus, and some sort of log monitoring on all those windows servers; whereas, on Linux systems anti-virus is more of an “option” according to PCI. Also Linux has native syslog capabilities built in whereas Windows does not. All of these factors can add to or reduce the total cost of ownership of a disaster recovery product.

Through the rest of this series we will look at three products that are the leaders in the disaster recovery space for VMware.

VMware SRM running (on top of vSphere replication)

Veeam Backup and Recovery

Zerto Virtual Replication

Without saying another factor to consider is price for the solution. Generally the tighter the RTO and RPO the solution provides the more expensive it will be. However list pricing isn’t always cut and dry when considering total cost of owner ship added to the cost of potential gains in RTO and RPO. In addition various software vendors pricing models lend them to a specific virtual machine configuration. If you have a virtual environment with fewer larger servers product X maybe more favorable from a cost perspective. If you have a virtual environment with smaller server product Y’s pricing model maybe more favorable.

View the above chart of the quick and dirty of the three technologies we will be diving into over the next few weeks in our series.

Disaster recovery is a challenging project, but thankfully there are more options than ever for businesses to select from. Many of them are technically sound and will accomplish business goals. Many times it comes down to selecting the right architecture and price model for your business.

Originally published here: https://simplecontinuity.com/disaster-recovery-for-vmware

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Most VMware administrators have heard of Site Recovery Manager (SRM). SRM has been the standard in disaster recovery for some time. It plays into VMware’s parent company’s (EMC) product line, traditionally leveraging storage based replication. This architecture leverages write journaling technology we spoke of in our first article in the series, so Recovery Time Objectives (RTOs) and Recovery Point Objectives (RPOs) could be very aggressive.

The down side to this architecture is that the customer has to have similar storage arrays at both the production and disaster recovery site. If for example the customer had a fiber channel array on the production side, and a lower grade NFS array from a different vendor on the other side SRM was not compatible Bummer…

VMware however released vSphere replication in the vSphere 5 family suite and allowed administrators to replicate their virtual machines without common storage subsystems. What this means is that you could have your traditional fibre channel SAN on the production side, and NFS, or internal storage on your disaster recovery site. The underlying storage type is completely irrelevant as long as the workload is supported. This is a gift for DR budgets everywhere. Additionally you can recover to previous points in time using snapshots at the recovery site much the same as you would use a traditional snapshot.

SRM in thie configuration sits on top of the vSphere replication instead of RPAs that are common in array to array based architectures. These replication appliances are Linux virtual machines that are deployed in the VMware environment. I will give VMware a large amount of credit here, where some competing technologies are cumbersome to install, vSphere replication installation takes only a few mouse clicks. Your vSphere replication appliances are functional in just a few minutes. Replication can be configured through the VMware fat client or the web client.

So what’s the catch? vSphere replication would fall into the snap and replicate category. This means that RTOs and RPOs wont be as aggressive as with array to array based replciation, or hypervisor technologies that use write journaling. The current RTOs and RPOs that can be achieved by vSphere replication with SRM over vSphere replication is 15 minutes. There are rumors that this will be coming down to 5 minutes in the future, but it’s only a rumor at this point. Also if you are trying to move to the web client then you will dismayed to learn that SRM can still only be managed through the VMware fat client. I don’t know to many administrators that are excited about the web client, but it’s a relevant piece of information for your day to day work.

So what about the licensing and additional costs? There are pros and cons to the vSphere replication / SRM model.

The virtual appliances are Linux based – pro

This means there aren’t additional Windows licenses required to operate the environment. Some of the other products use Windows based virtual appliances. When you have to stand up more Windows servers you have to patch and manage them, this adds to the cost of the solution. SRM can generally be installed on your Windows system that vCenter runs on. If you’re using the Linux based vCenter appliance SRM isn’t compatable. I would expect this to be resolved soon as VMware is trying to eliminate the need for Windows systems in the environment.

The base vSphere replication is free – pro

Yes you heard that correct, vSphere replication is free. If you have lower priority virtual machines you don’t have to buy SRM licenses. This means you can save money and buy only the SRM licenses (sold in packs of 25) for your mission critical VMs.

SRM is the orchestration tool on top of vSpherer replication – nutural

SRM and all of it’s power can be scoped down to only the systems you need it for. I personally like the flexability and choice, most companies don’t need to replicate all of their virtual machines with very tight RTOs and RPOs. If you are trying to replicate your entire VMware environment, you maybe better off with a solution that licenses by socket as it maybe more cost effective.

Snap and replicate technology – con

At the end of the day snap and replicate technologies are limited. Because the recovered virtual machine ends up with snapshots scalability can be an issue. Let’s look at an example.

VMware recommends that you only have 21 snapshots at a maximum using vSphere replication. More snapshots than this can lead to snapshot consolidation issues. If you wanted to have a recovery point every hour, you wouldn’t be able to recover your virtual machine to a point further back than 21 hours. This a limitation of any snaphost based replication technology not a defiency with in SRM or vSphere replication.

Scalability – neutral

The upper limit to SRM with vSphere replication is 1000 virtual machines. This will suit most enterprises; however, for very large scale deployments this may not be enough. SRM with storage array replication for example can support up to 1500 vitual machines. This limit is roughly about what you would get with any other snap and replication technology. In my personal experience Veeam starts to have problems after 300 virtual machines in a single instance.

Speaking of Veeam this is the next technology that we will discuss. Veeam is a good product that not only provides DR capabilities, but also a very mature backup solution. Join us for our next article in the series.

Originally published here: https://simplecontinuity.com/dr-for-vmware-srm-on-vsphere-replication/

What is most valuable?

What needs improvement?

For how long have I used the solution?

What do I think about the stability of the solution?

What's my experience with pricing, setup cost, and licensing?

What other advice do I have?

What is most valuable?

What needs improvement?

For how long have I used the solution?

What do I think about the stability of the solution?

What do I think about the scalability of the solution?

How are customer service and support?

How would you rate customer service and support?

Which solution did I use previously and why did I switch?

What other advice do I have?

What is our primary use case?

What is most valuable?

What needs improvement?

For how long have I used the solution?

What do I think about the stability of the solution?

What do I think about the scalability of the solution?

How are customer service and technical support?

How was the initial setup?

What about the implementation team?

What's my experience with pricing, setup cost, and licensing?

What other advice do I have?

Which deployment model are you using for this solution?