From the Chief Technology Officer at Marathon Technologies

Jerry Melnick

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Q & A from the August 19th Webinar

Thanks again to those who joined us for last week’s webinar, “How to Get at Least 2x Greater Cost Savings from Server Virtualization.” An on-demand recording is available to watch at your convenience (just click the link.)

We had a lot of good questions from our attendees during the Q&A portion of the webinar, which are summarized below.

How does everRun synchronize and how often?
everRun synchronizes as the data is written to the virtual machine. It’s not done on a time stamp. It is synchronously written to both physical hosts. We do a bit check to make sure both sides are written prior to responding back to the application, stating that it has been written, so that the data is always in a constant state and there is no data loss.

If I already have XenServer installed, can I install everRun on top of it, or do I need to reinstall XenServer?
everRun can be installed into existing XenServer environment. We do have resource pool requirements, so as long as you in a resource pool or can join yourself to a resource pool with a second server, or multiple servers for multiple host pools, we can be installed into an existing XenServer environment.

How does it support local storage? If the server that is hosting the storage goes down, what happens?
We mirror the virtual machine across two servers, so there are two copies of your virtual machine. Where we sit in dom0 (Xen domain zero), we have filter drivers sensing that type of situation. When using Level 2 protection with everRun, if you lose local storage, we leverage the copy of the info on the second server for zero downtime. If you were to lose the entire server, it would failover to the other side and start in Windows services. In Level 3, the same procedure applies to local storage. If you were to lose the entire server with Level 3, everRun allows it to simply continue functioning because we are running active-active.

Have you used this with a building automation system, such as Andover Controls Continuum which runs on a SQL Server?
We have a very large building automation practice here at Marathon and have worked with all flavors of SQL server. We have been working for years with building automation and security companies such as Johnson Controls, Tyco, Andover Controls, Siemens and many others. As long as the building system runs in Windows Server 2003 or 2008, we can provide availability for it with no custom scripts or custom coding.

What's the overhead with regards to CPU, memory, disk space of the host?
Generally in the 3-5% range. We’ve done some performance testing on XenApp and Exchange. You can download the results papers here:
Understanding and Characterizing Performance Implications for Running Exchange 2007 with everRun
XenApp 5.0 High Availability Performance

Can everRun be used with homegrown or custom applications?
Yes. everRun is completely transparent to the application and can support any and all Windows applications without any modifications, customizations, or scripting.

Can everRun protect a workload that is physical on one side and virtual on the other?
We do not support P2V today, but we have an ongoing research project on this topic. You can contact your sales rep for more info.

What is the maximum number of workloads that can be run using everRun?
The best way to answer this is to look at your virtualization planning assessment, including power capacity planning and hardware capacity planning. If you can support 10 virtual machines on a server, then you can support 10 virtual machines protected by everRun on that server with no problem. We also require a similar machine as the secondary server running on the same resource pool. It really comes down to how much your hardware capacity can handle.

How to take care of software corruption?
Because we are a synchronously written high availability solution, if there is software corruption on one side, we are going to replicate it to the other side. We sit at an asynchronous block-level filter driver location, so we have no ties to the software. So if it corrupts, it will corrupt on both sides.

Are you currently developing for Exchange 2010?
Yes, everRun will support Exchange 2010.

Does everRun support Small Business Server?
Yes we do. We’ve tested and qualified it for 32-bit and 64-bit versions of Windows Server 2003 Small Business Server Edition.

Does everRun replicate all server data including application data like a SQL database?
Yes. We replicate synchronously at a block level. We sit inside dom0. We then send the info block level to the other side. We do a block check and then we check our bit map to make sure the blocks are synchronously written on ongoing basis.

Can everRun be installed on top of XenServer 5.5 ?
Yes. We will support 5.5 in our next release scheduled for September.

Can we achieve DR?
Marathon offers a couple of options for disaster recovery (DR). Our SplitSite product can be used for metropolitan/campus DR, up to 150 miles apart, depending on your network conditions. We also offer everRun DR, for DR sites that are more than 150 miles apart.

Is the disk mirroring full copy or delta?
Upon initial protection we do a full copy. After you have a failure, such as an iSCSI card failure, we will do a delta copy back over to what’s missing. If you lose the entire RAID set, then we will need to do a full copy again.

Is the price of implementation based on the server capacity?
You need to purchase a license for each server in the pool. In terms of virtual machines (VMs), the license covers as many VMs as you can support in a box.

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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.