VIRTUALBOY BLOG
I’m going to try to make this a feature that rolls on and on in the future, as it’s an area I’m getting more and more questions about, and there are a number of options out there for Partners and Customers, so trying to centralise the info into one place should make things easier. I’ll try my best anyway!
Firstly, a bit of background. Why do we need Site Recovery? Well, think about it – lots of organisations are virtualising, which means they’re placing more eggs, in fewer baskets, however, at the same time, they are benefiting from features like Live Migration and High Availability to ensure uptime is as high as possible. What would happen though, if their site lost power? Well, for a short time, the UPS will keep you going, but before long…the SAN – gone. Servers – gone. Switches – gone. The site is down – even High Availability won’t save you there. Well, local High Availability won’t.
Multi-site Clustering
A feature of Windows Server Enterprise, since, well, 2003, has been Multi-site Clustering, or, as it has been known, Stretch Clustering, where you’re effectively stretching a cluster over WAN distances. Problem with 2003 Multi-site clusters, was the requirement, among other things, for a single-subnet environment across the WAN. In 2008, and subsequently in R2, this requirement no longer exists, but can be used if required.
From here
“The concept behind failover clustering across multiple sites is very simple. Why have separate islands of management for HA and DR? Why not take your HA setup and extend it to another site, thereby obtaining the added protection of geographic distance? Having a single management interface with failover automation provides an easy-to-use solution that gives you the best of both worlds. Multi-site failover clustering does exactly this. Multiple local nodes provide traditional HA functionality in the event of local server failure. Local application migration (from physical server to physical server) is also available for zero-downtime server maintenance. The cluster is then extended to another site. The process is as easy as adding another node to the cluster. It even works across different subnets, thus eliminating the need for stretched subnets. Multi-site failover clustering can be used to protect key Microsoft Windows workloads such as Microsoft SQL, Microsoft Exchange, DHCP and WINS services, file sharing, print sharing, etc”.
And now Hyper-V.
The key element that the in-box feature does not orchestrate, is the failover of the storage. Think about it for a second – Site 1 is your active site, and has a SAN in Read/Write, along with nodes actively hosting VMs. The SAN is being replicated to Site 2, where the SAN is in Read mode. Site 1 goes BOOM. What orchestrates the SAN switchover? What orchestrates the connection of replicated LUNS to standby nodes in Site 2? These are just 2 of the factors that need to be considered, and factored in, when planning a Multi-site configuration.
No Second SAN?
What about smaller environments, that don’t have the infrastructure, nor the budget, to house a second SAN and associated cluster nodes in another site? Can they not achieve site resiliency? Of course they can – there are a number of options available to them, from vendors like FalconStor, DoubleTake, and Steeleye to name but a few. I’ll focus on a few of these in later parts of this feature series.
For more information on Multi-site clustering, you may find the following resources useful:
Essentials for Hyper-V
Before we go into the specifics around Site Recovery, it’s important to expand on what Essentials for Hyper-V actually is, as it’s more than just Site Recovery. From the Citrix Essential for Hyper-V website:
So, 6 technologies in there, each with significant benefits of their own (of which the links above will provide you with more information, but what about pricing and versions?
As you can see, the Express Edition provides the StorageLink technology, which provides Windows administrators running Hyper-V virtual machines the ability to dramatically simplify their storage management processes with quick and easy storage configuration and provisioning for their Windows Server 2008 Hyper-V and System Center virtual infrastructures. Citrix Essentials helps Hyper-V administrators take full advantage of powerful storage-based features like deduplication, thin provisioning, cloning, snapshots and replication. You can get more info on Express here, but remember, the Express Edition of Citrix Essentials for Hyper-V supports up to two Hyper-V servers and one storage array. If you need more, you’ll have to look at the Enterprise of Platinum Editions, which are priced at $1500 and $3000 per host respectively. At $3000 per Server, it compares pretty favourably with VMware SRM from a pricing perspective, with SRM coming in at $2118 per CPU (inc 1 year Gold S&S), up to $2867 per CPU (inc 3 year Platinum S&S), which, for a typical 2 CPU box, would mean $4216 and $5734 respectively, but remember, for your $3000 per server, you’re also getting 5 other technologies thrown in too…
StorageLink Site Recovery
Now, I’m going to take a large amount of the following information from the Citrix Essentials for Hyper-V website – the point here is, I’m not trying to reinvent the wheel here – I just want to try to centralise the Site Recovery related information into one place.
Citrix StorageLink Site Recovery dramatically simplifies the setup and configuration of disaster recovery protection of Hyper-V workloads through direct integration with storage array-based controls for data replication and copy services. Together, Microsoft Hyper-V and Citrix StorageLink Site Recovery reduce the cost and complexity of implementing disaster recovery for critical server workloads
What about other benefits?
What about requirements?
The following are the basic requirements:
Once organizations have the basic Citrix and Microsoft components in place, the implementation of disaster recovery protection is very easy:
Summary & Resources
One key thing to remember, is that the Site Recovery elements described above, apply to a Windows Server 2008 Hyper-V environment, not R2. There is an updated version on the way, for the whole of the Essentials for Hyper-V suite, with more information available here. The release, known as Citrix Essentials 5.5 for Hyper-V, takes advantage of the new R2 capabilities of both Hyper-V R2, and System Center Virtual Machine Manager 2008 R2, and you can download the beta here. I’ve not seen Site Recovery listed in the beta release, so at this time, I can’t confirm it’s in there, although the download page indicates it’s present.
In terms of resources available:
Dear,
Can you also run StorageLink Site Recovery when you use Citrix Xen as hypervisor and not Hyper-V ?
Kind regards,
Kenny
Hi Kenny,
Looking here: http://www.citrix.com/English/ps2/products/subfeature.asp?contentID=1680964 i don't know if the Site Recovery bit has been brought into Essentials for XenServer yet. StorageLink API's are there, but not the failover unfortunately.
Cheers,
Matt