From the Chief Technology Officer at Marathon Technologies

Jerry Melnick

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Q & A for the April 16th Webinar: Fault Tolerance in 10 Minutes or Less!

We had an incredible amount of great questions during the Q & A session of our April 16th webinar with myself, Michael Bilancieri, along with John Humphreys of Citrix Systems and Doug Strain of HP. I’ve posted the questions and responses here on our blow for everyone’s benefit. This webinar was recorded in case you weren’t able to attend, click here to view the webcast!

Q: Is everRun VM ready to work with free of charge XenServer?
A: The new version of everRun VM software (available mid-May) works with the new free enterprise-ready version of Citrix XenServer as well as Citrix Essentials.

Q: Is a SAN required to implement these fault tolerant solutions?
A: No, SAN is not required, but is certainly supported.

Q: How is everRun VM licensed?
A: everRun VM is licensed per XenServer host for level 2 protection, with level 3 protection being licensed per each VM you wish to protect with complete system-level fault tolerance.

Q: How much does the license for everRun cost? Where do I go for everRun Pricing?
A: Pricing for everRun VM starts at $3000 per XenServer host. For more information, please contact Marathon Sales Department at 888-682-1142 or info@marathontechnologies.com , or contact your Marathon reseller.

Q: How does everRun synchronize, and how often?
A: everRun VM performs an initial mirror of the entire VM upon protecting it and continuously mirrors it in a synchronous manner to ensure that the two paired systems are always identical.

Q: What are the overheads CPU, memory, and bandwidth for running everRun?
A: Overhead varies depending on the hardware, storage, applications and load. We will have performance data available shortly that shows the variance between a standalone VM and one that is protected with everRun.

Q: To summarize Marathon Technologies’ solution, is it replication of VMs between two VM Hosts? How much resource does this take away from VMs / VM Host?
A: everRun is not a replication technology, but rather a fault tolerant solution that offers the ability to synchronously mirror the entire VM between two physical XenServer hosts. Should one host suffer a component or even system failure, everRun VM allows the application to continue running without interruption. Here is a flash demo that explains how everRun VM works. Overhead varies depending on hardware, resources, and application load. We are currently benchmarking performance characteristics and should have them available within the next few weeks.

Q: Does the restart disconnect users connected?
A: For most hardware failures, there is no restart. everRun VM simply redirect I/O (storage and network) to the secondary host. If level 2 protection is utilized and a host is powered off, there is a brief interruption while the VM is restarted on the secondary host. With level 3 protection, there is no interruption even when a host is powered off.

Q: How many servers can you have in a pool?
A: everRun VM is qualified for up to 4 XenServer hosts in a single pool.

Q: Does everRun provide offsite datacenters which host VMs? Or do they offer software, or both?
A: everRun is a software solution that mirrors the entire VM to a secondary XenServer host either locally or at a remote location. We do not offer hosting services.

Q: Does Citrix FT/HA need shared storage?
A: There are three levels of protection available within everRun VM; levels 1, 2, & 3. Level 1, XenServer HA, is included as part of Essentials for XenServer and does require shared storage. everRun adds level 2 and level 3 fault tolerant capabilities and allows the option of using shared storage or independent storage between which everRun will synchronously mirror the entire virtual machine and all its data.

Q: Any migration tools off VMware?
A: There are a number of migration tools that can perform virtual-to-virtual (V2V) migrations from VMware to Citrix XenServer where they can then be protected by everRun VM. Please contact Citrix or Marathon for further details.

Q: Does Geographic Fault Tolerance require the two servers to be on the same subnet or can they be across routed networks?
A: Yes, the servers within an everRun configuration must be in the same subnet or on a common vLAN.

Q: What is the support for Windows Server 2008 timeframe?
A: The new version of everRun VM (available mid-May) will support Windows Server 2008.

Q: Does Marathon’s product protect SMP VM’s, or just single processor VM’s?

A: everRun can support multi-processor VM’s.

Q: With everRun, is it possible to sync VM’s across a WAN without SAN block replication? ie: local storage to local storage?
A: Yes, everRun will mirror the entire VM, including OS, application, and data, between two XenServer hosts with separate storage. These two systems are kept synchronized continuously.

Q: We have a custom application we currently run on a MS active/passive cluster. One of the useful things is we can update the code on the passive node, flip to it and if there is any issue, easily flip back to the original node. Is there a way to do this with everRun? ie: “pause” the sync and flip which is active VM?
A: For upgrades, everRun allows one side of the pair to be taken offline for applying and testing upgrades before applying them to the live running system.

Q: Is everRun part of Essentials, or is this a different product add-on? Does it require Essentials or just the hypervisor if it’s an add-on?
A: everRun is a separate product from Marathon Technologies and is not included in the Essentials offerings. everRun does support the Essentials offerings as well as the free edition of XenServer. everRun is simply installed on top of XenServer.

Q: Can you confirm that Marathon HA is an existing part of Citrix Essentials?
A: everRun VM is not bundled with Citrix Essentials for XenServer, however it can easily be installed on an Essentials deployment. Citrix Essentials for XenServer does include level 1 or auto-restart HA (XenServer HA) which was jointly developed by Marathon and Citrix.

Q: I have a question about switching virtual IP or domain name to the remote standby site in case any disaster happens to the primary site. Is this handled automatically without human interference? How is DNS cache updated in the domain name servers across the world?
A: everRun VM is a synchronous solution and as such has fairly stringent requirements for network latency. everRun VM is not a DR solution that can protect systems across thousands of miles, but rather a disaster tolerant solution that allows regional or metropolitan separation. The XenServer hosts being used by everRun must be in the same subnet or common vLAN, so there is no need to make DNS or Active Directory updates when the primary host/location fails and the VM is started on the secondary XenServer host. All error detection and error handling are completely automated with no human intervention required. For long-distance replication and failover, Marathon does offer an asynchronous DR solution.

Q: Regarding the Marathon HA tool; if your HA tool handles auto failover across sites by replicating the VM files at storage level, how do you manage the network differences (for example, how will tool know which IP address etc to assign to the mirrored/recovered VM) ?
A: everRun VM requires that the servers in the everRun pool be in the same subnet or common vLAN. This allows use of the secondary server and its components without any need to change any networking records or clients to point them to the secondary system. The VM/application environment are identical regardless of which XenServer host they may be running on. The IP address, hostname, and even MAC address are always the same, making any I/O redirection or VM failover completely transparent.

Q: If I have 24 VM’s that are hosted 3 XenServers won’t providing everRun as a fault tolerant solution require me to double up on XenServer hosts to accommodate mirroring VM’s across numerous hosts?
A: The number of VM’s possible is dependent on numerous factors, including hardware and application loads. everRun VM does create a mirrored VM on a secondary host. If there are enough resources available within your three hosts, you shouldn’t need additional hosts.

Q: Does Marathon have plans to support Linux based VM’s?
A: Yes, we do plan to support Linux VM’s but do not have a delivery date scheduled at this time.

Q: Does the everRun product (or another Marathon product) allow Linux virtual machines to run fault tolerant (zero downtime with a physical host failure)?
A: everRun VM does not currently support Linux VM’s, however the level 1 XenServer HA capability available within Essentials for XenServer can protect Linux VM’s.

Q: Fault tolerant VM replication is great, but does XenServer + everRun have a restore point like solution for guest OS corruption\malfunction?
A: everRun VM is licensed per XenServer host for level 2 protection, with level-3 protection being licensed per each VM you wish to protect with complete system-level fault tolerance.

Q: How does everRun differ from Double-Take?
A: everRun VM is a fault tolerant availability solution, while Double-Take is a replication and failover solution designed for long-distant DR. For DR needs, Marathon offers everRun DR, which provides similar capabilities to that of Double-Take.

Q: Referring to the two DL380 servers in your slide… What physical hardware is used to allow the two servers to communicate with each other?
A: The XenServer hosts within an everRun VM configuration are connected either with a direct-attached crossover using GigE interfaces when the pool consists of two XenServer hosts. If there are more than two hosts in the pool, these networks will need to be configured through network switches. We refer to these connections as Availability Links, or A-links.

Q: Is there a Sullivan Group case study or whitepaper?
A: You can view The Sullivan Group case study here. You can also read the other case study we talked about in the webinar, how Argo Capital uses everRun VM to protect Exchange, BlackBerry Enterprise Server and Citrix XenApp, here.

Q: In the pictured scenario of 2 Proliant DL380’s, does the everRun use local storage on each server, or does it use shared storage?
A: everRun has the options of using either shared storage or local independent storage.

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Jerry Melnick (jmelnick@us.sios.com) is responsible for defining corporate strategy and operations at SIOS Technology Corp. (www.us.sios.com), maker of SIOS SAN and #SANLess cluster software (www.clustersyourway.com). He more than 25 years of experience in the enterprise and high availability software industries. He holds a Bachelor of Science degree from Beloit College with graduate work in Computer Engineering and Computer Science at Boston University.