Blog Entries in Data Replication

Monday, May 24th, 2010 - 11:58 am EDT

The Changing Dynamics of Data Protection

Posted by: Michelle Liro

Frank Ohlhorst, former Executive Technical Editor for eWeek and award-winning IT expert, was our expert guest speaker this week for the webinar, “Cut Your DR Costs and Get Better Data Protection.” During his presentation, Frank reviewed why he believes that now is the time to rethink traditional approaches to disaster recovery. He explained why the total cost of ownership for disaster recovery solutions is on the rise, and why changing data protection dynamics are making it more economical to focus your time and budget on the prevention of downtime and data loss, rather than recovery.

Below is the summary of the audience questions from the Q&A portion of the webinar.

Q: You talked about how HA can give you a geographic advantage. What do you mean by that?
Frank Ohlhorst: High availability systems are designed to work with multiple servers and there’s no reason why you can’t have those servers located hundreds or thousands of miles apart. You get a geographic advantage because your data centers is in multiple places and regional areas, so if a weather-related or other event occurs, let’s say a blizzard up north with a power outage, your data center down south can pick up the slack without kicking users off the system. The same can be said about a data center located in an area with hurricanes or other natural disasters. The geographic separation gives you added protection.
When high availability is paired with load balancing, it helps to locate the data resources closer to where the users are requesting them. Let’s say you have users in Utah, it’s better performance-wise to have them talk to the data center in Nevada rather than Virginia. It helps on that level also. HA solutions also have the tools for monitoring what is going on with your users and network, to help you plan out how you should assign users to specific data centers for the most efficiency.

Q: I understand how high availability can handle unplanned downtime, but what about planned downtime? Can it help there as well?
Frank Ohlhorst: Yes, the idea there is being as you have multiple active systems to meet the user’s needs, you can take one of those systems down for maintenance and have the users serviced by the active machines while you make the updates and improvements. Then when you are done, just resynchronize with the other systems, move the users over to those systems and update the rest of the servers.
Another great benefit of this is for testing upgrades and changes. So take one system offline and test your upgrades to see if they work properly before you return that system to production.

Q: If I have an HA solution in place, is back-up still necessary?
Frank Ohlhorst: 99% of the time the answer to that question is yes. It depends on what your corporate needs are. There are certain situations where HA might not deal with your catastrophe. Those are usually software-damaging events, like a virus infection, that winds up getting replicated across the system. Of course, that should really be part of your security planning to prevent events like that from even happening. With today’s security technologies, it’s pretty easy to prevent that. But if you did ever have one of those events, you do need something to roll-back to, and that’s where the back-up comes in to play. Ideally though, you should be preventing that type of event, because you also have the potential to lose active data if that happens. When it comes to compliance or auditing, you have to restore data relevant to that time period to meet the needs of e-discovery, compliance, accounting audits and other similar requirements. So you can’t just say, “I have HA in place, so I don’t need to back-up.”

Q: What about data de-duplication technologies, don’t they help solve this problem of managing large volumes of data?
Frank Ohlhorst: They reduce the data footprint for sure, but what we’re talking about here is availability of the data. They can certainly reduce the size of your data footprint, you can use de-dup to speed up backups. At the end of the day though, if the system or application is not accessible to the user, then it’s not available and you haven’t met your objectives. It’s a simple matter of business logic that data de-duplication can improve performance and reduce the size of the footprint, but it doesn’t solve the problem of providing access to users during catastrophic events.

Q: Do you see continuous availability and high availability as the same, and if so, how do you differentiate between the two and the costs?
Frank Ohlhorst: There was a time when those technologies were very, very different. That was way back when we relied on expensive hardware-based solutions or appliances that provided continuous availability. High availability at that time was thought of as a method to switch from one server to another using a manual process in the case of an emergency.

High Availability technology has evolved significantly since then. Now, the two are really one in the same from a planning and software point of view. Today’s HA solutions eliminate that step of manual switchover. What you see with the vendors today is automatic HA technology that really delivers continuous availability. And the cost gap today is pretty much zero, since the technology for continuous availability and high availability has evolved to be almost one in the same.

Q: With an SRDF/S-type solution, how can we get around the fact that being geographically more separated to mitigate regional disruptions can mean slower primary system response times due to the need to remain synchronous?
Frank Ohlhorst:
Let’s look at this first from the ideology of what we’re trying to do which is business continuity. So, if you encounter a situation when you lose connectivity to a system and it’s still available at another location, then you’ve met the goal there of providing continuity. And you’re in much better shape than you would be at that point if you had a disaster recovery solution instead of a business continuity solution.

The question you have to ask yourself at that point in time is: Is reduced performance better than no performance at all? For most businesses, the answer is yes. For others, if the performance lag is significant enough it can impact business. In those cases, you’ll have to work out a way to develop geographically dispersed sites can that can provide enough performance to the user sets that need access to the data. You also need to make sure that your connectivity has enough bandwidth to support your BC/HA solutions, which means the ability to replicate the data in real time across the wire. You might have to invest in larger pipes for better connectivity to support that. But again, that depends on your particular business and your needs. There is no one correct answer to this question, but the good news is that there are several solutions today that can help you solve this problem and meet the levels of availability that you need for your business.

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Disaster Recovery  Availability  Business Continuity  Continuous Availability  Data Replication  Disaster Tolerance  Fault Tolerance  High Availability  Interview  Webcast  Webinar 

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Monday, September 21st, 2009 - 9:40 am EDT

Q&A: Windows Server High Availability

Posted by: Michael Bilancieri

Thanks again to those who joined us for last week’s webinar, "Windows Server 2008 High Availability: Technology Comparison." The on-demand recording of last week's webinar is now available to watch at your convenience (here).

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

Q: How do you determine when to use an HA solution vs. a DR solution?
When it comes to availability vs. recovery, the most important question to ask is what are your recovery time objectives (RTO)? What is the amount of time your application can afford to be down? If the applications have strict requirements, then you want an availability solution. Disaster recovery is data replication often times with a failover capability, not availability. For critical applications, this may not be sufficient.

Q: If I have an HA solution in place, do I still need a solution for backup?
Availability and backup are two different things. That question comes up a lot, along with the need for disaster recovery. Backup will never likely go away completely. You still need to backup your data to ensure recovery in the future should that be necessary.

Q: Is everRun available for Linux applications?
Yes. We can provide basic failover capabilities for Linux applications today.

Q: How does everRun differ from replication solutions?
everRun 2G is used for availability, both locally and for short-distance geographic separation as well. We have a replication and recovery solution as well that can be used for disaster recovery for long distances. You should determine what your objectives are: do I have to keep my applications up and running or do I just need to recover it if something fails? What’s the recovery time objective for each application? It’s up to your individual applications and what level of protection you need for each. Often times availability is a priority as downtime is not desirable, with DR also a requirement on top of that to ensure recovery in the event of a major outage.

Q: Can everRun be used for planned downtime (i.e. to keep one host running for end-users while the application on the other host is being upgraded)?
Yes, everRun can be used to help facilitate certain system updates to reduce interruptions and mitigate risk.

Q: Can it work between two virtual machines and on x64 based systems?
Yes, we support XenServer and 64-bit hardware and Windows Server environments.

Q: What is the performance impact of using everRun 2G?
That’s variable depending on your application. It can be anywhere from 3-15%. We’ve done some performance testing specifically on XenApp and Exchange. You can download those white papers here:
Understanding and Characterizing Performance Implications for Running Exchange 2007 with everRun
XenApp 5.0 High Availability Performance

Q: Does Marathon offer backup solutions for everRun users?
We have methods to backup your systems and we’re working improving on our current offerings to make them quicker, easier and more granular.

Q: Can everRun work with dissimilar hardware? Can everRun work with more than two servers?
From a server standpoint, you just need similar processors; storage does not need to be similar. You can have SAN on one side and NAS on the other or any other combination. On the second question, yes, everRun will work with more than two servers. You can build a pool of servers and protect within that pool.

Q: Does everRun have backward compatibility with older OS?
Yes. It will work with Windows Server 2003, and also Windows Server 2008.

Q: Can everRun run on the Foundation Server Edition of Windows 2008?
It does not. everRun supports the full implementation of Windows Server 2008. everRun runs underneath Windows, it does not install into Windows.

Q: How does everRun handle data stored on NAS?
Storage is transparent to everRun. We look at storage as just a LUN.

Q: What is difference between everRun HA and everRun 2G in Windos Server 2003?
The differences are the ability to create multiple workloads. HA can protect one workload. everRun 2G can protect multiple workloads. There is also a new and improved graphical interface with better reporting and management capabilities.

Q: Does everRun work with XenServer 5.5?
Yes, everRun works with XenServer 5.5.

Q: Are there any changes in WS 2008 & WS 2008 R2 in the way that HA improves?
Yes. You can find an overview of those changes directly from David Hanna of Microsoft in our recent webinar and white paper “The Top 10 Reasons to Upgrade to Windows Server 2008.” You can also read the Q&A with Microsoft from that webinar here.

Q: Is everRun 2G available for Microsoft Hyper-v?
We will provide support for Hyper-v in a future release.

Q: With applications using various DNS names, how does this solution integrate with DNS changes? (failover to remote office for true DR-different IP/network)
everRun availability solutions pairs systems within the same subnet of vLAN, eliminating the need to make any DNS changes.

Q: Question is tied to what permissions are needed to do a recovery. For recovery in active Directory most items need to replicate around that there was a change and we do not want to hand out Admin control over the domain(separation of access)
everRun is designed to not require any changes to Active Directory during or after a failure or recovery.

 

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Availability  Continuous Availability  Data Replication  Disaster Recovery  EverRun  Fault Tolerance  High Availability  Marathon  Webcast  Webinar  Windows 

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Tuesday, March 3rd, 2009 - 3:07 pm EST

Q & A for the February Webinar: Practical, Affordable High Availability and Disaster Recovery for a Tough Economy - Featuring Forrester Research

Posted by: Michael Bilancieri

We had a lot of great questions during the Q & A session of our February webinar with Stephanie Balaouras of Forrester Research. We’ve posted the questions and responses here on our blog for everyone’s benefit.

Questions from the webinar:

Q: In the architecture two "mirrored" VMs are shown which are connected. Does that mean that you have to install 2 application VM servers or do you have to install just one and Marathon makes the second?
A: You only need to create one application VM. After this is created, you can use everRun to protect that application. As part of the protection process, everRun creates a “cloned” instance of the application on the second host. The instance is completely identical to the original, with the same identity, MAC address, resources, etc. It is this redundancy created by everRun that protects the applications.

Q: In the Marathon license there is HA and FT. In which are the levels 1-2-3 available?
A: Levels 1, 2, and 3 are available in a single solution called everRun VM and any level of protection can be enabled on a VM. everRun VM level 3 protection will be available in Q2.

Q: The licensing question you just answered seems different from what you used previously. You previously only had to license the VMs OS in a fully protected system. Please explain.
A: Microsoft licensing requires a valid Windows license for each side of the protected VM. Using Enterprise Edition can reduce the number of licenses required. Please refer to Microsoft licensing terms for specific details for your environment.

Q: How does the software communicate between disparate storage NAS to DAS, SATA to Fibre Channel?
A: everRun does not limit you to needing matching storage requirements on multiple hosts. Communication between hosts is done through Availability Links (A-Links), which are private networks between each host. everRun handles the mirroring at the host level, passing I/O through XenServer to write to the disks. The type of disk or connection is not relevant.

Q: How does this compare to VMWare's SRM & VDM products?
A: VMware SRM provides a mechanism to restart a VM on an alternate host, however it relies on other storage mirroring solutions (often within the storage system) to perform the mirroring. SRM does not move data or provide a comprehensive HA or FT solution.

Q: Is the product host based or a fabric based solution?
A: everRun VM is a host based solution, with a minimum of 2 hosts required.

Q: Do you need to keep a warm copy of the applications at the DR site?
A: During the protection process, everRun takes the chosen VM and clones it to the designate secondary host. This creates a complete and identical instance on the secondary host. everRun maintains these two synchronously so that they are always identical. everRun’s unique architecture exposes these two mirrored instances as a single entity; there is no need to install, manage, or update both sides, only the one single instance of the OS/application. Should the entire ‘primary’ host fail, the ‘secondary’ host will immediately start the cloned version. It comes up with the same IP address, hostname, and MAC address of the primary so that there are no client-side, DNS, Active Directory, or other infrastructure changes required.

Q: Is the DATA synchronous like SRDF or near synchronous?
A: everRun performs synchronous mirroring of the entire Windows environment, including the OS, application, and data.

Q: How does this compare to products like RecoverPoint/Replistore, InMage, Neverfail, Falconstor etc?
A: These products are disaster recovery products intended for long-distant asynchronous data replication and failover. everRun availability solutions provide true availability in a comprehensive and automated manner. Marathon also offers DR solutions for long-distant protection. Disaster recovery and availability are mutually exclusive in most cases and should generally be considered separately. They are complimentary more than competing solutions.

Q: What is the software support plan? What are the recurring costs for your product year to year?
A: We offer a Premier support plan or a Basic support plan. The only recurring cost year to year is the cost of support.

Q: What are the operating system requirements, how many copies of the OS do you need?
A: Each Windows environment is mirrored to a secondary host, requiring a second Windows license. Using Enterprise Edition of Windows allows for fewer licensed copies. Please refer to your Windows licensing terms for specific requirements.

Q: Regarding the 10ms sync time, what happens if that time increases to say 20ms due to network traffic?
A: If the latency increases beyond our requirement the paired systems may assume that one system is down and redundancy may be lost. In a properly configured environment the application should remain running while the secondary system is no longer maintained in a redundant fashion. Once the latency returns to within spec, the systems will re-sync automatically and return to a fully redundant state. Typically the application is not impacted.

Q: What are the bandwidth requirements?
A: Best practices state 155MB link between the two hosts. For local systems a simple crossover cable between the two systems is sufficient. When separating the systems the 155MB requirement becomes more relevant. This number can vary depending on the applications being protected and the amount of data being managed.

Q: Do you have instances of numerous geo-available solutions with specific applications?
A: Here are two examples:
MAN AG success story with everRun SplitSite
Chester County, PA success story with SplitSite

Q: Is windows Server 2008 VM supported? If not, why?
A: Windows Server 2008 64-bit will be supported in Q2 of this year.

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Availability  Data Replication  Disaster Recovery  EverRun  EverRun VM  Marathon  VMware  Webinar  XenServer 

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Friday, February 13th, 2009 - 1:49 pm EST

Q & A with Stephanie Balaouras of Forrester on High Availability

Posted by: Melanie Stec

On February 24th, we’re going to be doing a webinar featuring Stephanie Balaouras, Principal Analyst at Forrester Research and co-author of the report, X86 Server Virtualization for High Availability and Disaster Recovery. Stephanie was good enough to sit down with us to answer a couple of questions we had before the webinar.

Q: Stephanie, can you give us the 10,000 ft. explanation of why server virtualization is a good alternative for high availability and disaster recovery?

A: In a nutshell, server virtualization facilitates a rapid — or even automatic — restart of applications after an IT failure, and when used in conjunction with data replication between data centers, it can restart applications at a recovery site following a primary site failure. In particular, x86 server virtualization can improve the availability of business-critical systems that are important to the business but not critical enough to warrant the investment in expensive and complex resiliency technologies like fault-tolerant hardware or clustering.

Q: You had mentioned that Forrester is seeing increased customer interest in active-active strategies for high availability. Is that just in Fortune 500 companies or is the interest broader than that?

A: Active-active isn’t just for the largest of companies. Companies of all sizes are under increasing pressure to improve their recovery capabilities but at the same time, they are under pressure to reduce costs and achieve greater operational efficiencies. Companies need an alternate site so they can failover critical business operations in the event of a primary site failure. Given the necessary investment, an alternate data center simply can't remain idle waiting for some disaster to occur. Companies must determine ways to maximize this investment to improve business operations, accelerate growth, or elevate availability.

Q: What’s changed that is driving the greater interest in active active for HA?

A: There are a couple of reasons why there is a growing interest in active-active strategies. First, as I mentioned, most companies are under increasing pressure to improve recovery objectives. In fact, most companies that I speak with have recovery time and recovery point objectives measured in hours, not days. To achieve this type of recovery, today you need to have dedicated infrastructure (servers, storage etc.) at the alternate site.

In the past, many companies might have turned to a DR services provider for their needs. For cost reasons, they subscribe to shared infrastructure services. Because the infrastructure is shared, recovery is limited to recovery of system configurations and data from tape, which means that best case scenario for recovery is 24 hours to 48 hours. As result, many companies are brining DR “back in-house” and making the business case with better recovery objectives and the ability to use the investment in the alternate site for multiple purposes.

Thanks Stephanie, we’ll see you on the 24th. Want to hear more from Stephanie? View her posts on the Forrester Blog for IT Infrastructure & Operations Professionals.

Register here for the webinar featuring Forrester Research.

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Availability  Clustering  Data Replication  Disaster Recovery  High Availability  Virtualization  Webinar 

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Tuesday, August 14th, 2007 - 1:45 pm EDT

Data Replication

Posted by: admin

This is the term that has caused the most confusion within the market, yet provides the lowest level of availability and requires a fairly heavy implementation process. Data replication can be more accurately described as a data storage and backup strategy that involves moving data from one server to another server using an asynchronous model to allow for unlimited distances between servers.

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Data Replication  Glossary 

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