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How To Choose A Cloud When You Need High Availability

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How to Choose a Cloud when you need High Availability

How To Choose A Cloud When You Need High Availability

Understand the cloud market

A number of analyst firms are predicting an ever-increasing number of deployments of applications, databases, and solutions in the cloud. According to Gartner, firms are “moving to the cloud at an increasing rate.”[1] In fact, Gartner and other analysts expect the pace of cloud migration and deployment will continue to accelerate, driven in large part by the pace of innovation in the cloud. In a TechTarget article by Kurt Marko, of MarkoInsights, Marko notes that the pace of innovation that is “being undertaken in the cloud likely can’t be replicated on premises due to the elastic, scalable, and on-demand nature of managed public cloud services.”

We see more and more companies that had been using the cloud only for DevOps applications and databases that were not essential to their business, are now moving mission-critical applications, ERPs and databases that require high availability protection to the cloud.

If you are considering a move to the cloud – and it seems likely that you are – there are several keys to understand when you need high availability.

Familiarize yourself with the cloud high availability options

To plan for the proper availability solution for a cloud or hybrid cloud deployment, consider what the pain points are with regards to both availability (99.9% uptime) and high availability (99.99% uptime). You also need to understand the options that are available for high availability with an eye towards your plans to migrate to the cloud. Notable analysts and experts suggest looking for solutions that will not only mitigate and reduce the pain of migrating your workloads, but will also provide a balanced and comprehensive approach to availability throughout the lifespan of your cloud architecture. Note, it is also wise to consider solutions that can provide protection and high availability for portions of your workload that may one day repatriate from the cloud back to your on-premises environment.

Here are ten things to consider when comparing your availability options in the cloud: 

1. The deployment method. Is it possible to deploy the availability solution you are considering  using an image, CLI, UI, or other repeatable solution such as cloud formation template or packaged scripts.

2. The system requirements. Most notably, consider the operating system (OS), disk, CPU, and memory requirements.

3. The deployment environments. Do your availability options support on-premises only, one or more public clouds, or can they support a mixture, and/or hybrid cloud deployment. Is there a SaaS offering available as well?

4. The breadth and depth of application protection. “Breadth” meaning what types of applications, databases, front-ends, networking, and infrastructure components can be protected?  Is there a flexible framework for adding new applications and variants? “Depth” meaning – is the solution application-aware – and able to maintain application-specific best practices throughout the application failover/failback processes?

5. Performance requirements. We often think of RTO and RPO, but what about other performance needs of your solution. Will your availability solution cause performance issues on failover?

6. Resilience requirements. How large a cluster can the availability solution support?, How many faults and failures can it detect and recover from. How will replication be handled while keeping metadata in sync?

7. Supportability and maintenance. Does the availability vendor have experience with a wide range of availability needs and configurations? Do they have longevity, and a support system designed to address issues that may go beyond their solution? Can they help you minimize disruption and planned downtime during your system management and maintenance (patches, upgrades, and general maintenance).

8. Total cost of ownership. There are entire industries and services dedicated to helping you calculate the total cost of ownership, so we won’t cover that here. Suffice it to say, your calculations will be unique to your organization, cloud provider, applications, and IT team. You should consider whether your availability solution vendor can help you identify strategies for saving utilization, licensing, and other costs? Does the solution automate manual tasks, reduce IT labor time?

9. Licensing and pricing model. How do you consume the cost of the software? Is there a subscription fee, subscription model, pay-as-you-go offering, bring your own license (BYOL), or combination of flexible options. How will you enable the product licensing?  Is there a license server, licensing service, or encrypted key based on virtual machine deployment details, such as address, hostname, MAC address.

10. The impact on IT staff. How much training with the solution require? How much manual intervention will be needed in the event of an application failure event or disaster? Will it require specialized scripting that needs to be maintained? Who will be responsible for ongoing maintenance?

Weigh the benefits and trade-offs

Like every important decision, you need to understand your tradeoffs and choose the best balance to meet your needs. For example, I recently asked a friend to recommend a good walking shoe. I bought a pair he raved about – noting how lightweight they were, how strong and durable the fabric, and how stylish they were.  I went for my first long walk-run in them, and I donated my first pair of “one run” shoes immediately thereafter. When I went to ‘Fleet Feet’ to get an expert’s opinion I ended up with a heavier shoe, with more breathable fabric (also less durable), and an unrivaled level of hideousness. I made a tradeoff between appearance and function that worked for my needs and budget.

Like running shoes, there is no silver bullet solution that will be the right fit for every company, every application, every database, and every possible server and architecture. You are officially free to stop looking for it. Instead, settle into the activity of weighing the trade-offs to determine what is the right fit for your company’s needs. Think about your tradeoffs. For example, if you’re sure you will be a full Microsoft shop, the importance of GCP and AWS support should be a little lower in your evaluation process.

Take your IT infrastructure dynamics into account

Think holistically about availability in your entire IT infrastructure – both on premises and in the cloud. The reasons to do so are best explained with another analogy. In 2018, I was the coordinator for an outreach program feeding the homeless and hungry in Columbia, South Carolina. Our group met once a week to serve a meal and a message of hope to over 100 men, women and children. When we considered expanding – adding more days of the week, more hours, or additional services, we had to think well beyond simple scheduling requirements. Knowing that we were providing a critical service to clients who depend on us, we had to consider all the factors that affected our ability to deliver those services consistently for the long-term, such as: cost, ages of our team members, outside obligations, alternative methods to achieve our goals, risk factors, and other dynamics within our parent organization.

When you are choosing your solution, after you’ve understood the market, familiarized yourself with options, and weighed the trade-offs, the last step is to take into account the various other dynamics in your overall environment. Will the solution meet the needs of your business as a whole? Will your critical data be protected from loss? Will your end-user productivity be protected from downtime? What training will be required to move to the cloud and how will that impact your ability to manage or maintain the solution that you choose? What IT roles will be added, removed, or changed in your cloud journey?  Will any responsibilities for application availability move to any line-of-business owners? And how will the shifts in responsibilities, or team make up improve or decrease your overall potential for success. Consider whether your team needs to take a step-by-step approach, migrating smaller workloads first.

As VP of Customer Experience, I have seen a wide range of cloud migrating planning – some straightforward others extremely disruptive. In one instance a customers’ move to the cloud was highly contentious because management saw it as an opportunity to eliminate an entire IT department. I’m not suggesting that you play politics, but you should be aware of all of the factors at play in these complex projects.

Migrating to the cloud is supposed to save money, time and resources while affording improvements in availability and resilience. Regardless of which cloud you choose, make sure that you consider these tips and select the corresponding availability solution that gives you the flexibility to deliver the protection you need in the configuration you want.

Learn more about cloud high availability options with SIOS.

– Cassius Rhue, VP of Customer Experience, SIOS

Reproduced with permission from SIOS

How To Clone Availability In The Cloud With Better Outcomes

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How To Clone Availability In The Cloud With Better Outcomes

How To Clone Availability In The Cloud With Better Outcomes

Tips from the movies – Multiplicity

Multiplicity is a 1996 American science fiction comedy film starring Michael Keaton as Doug Kinney, a busy construction worker struggling to make time for his family and his demanding job. When a scientist offers to clone him, Doug agrees to just make meeting his schedule and commitments easier. But then the copies of him begin making copies of themselves. By the time the last copy is made, the point is clear. Cloning may not be all it’s cracked up to be, or at the very least comes with some strong warnings, challenges and side effects. The famous original Star Trek episode “Trouble with Tribbles” illustrates a similar point.

Like cloning on the big screen (or small), cloning in the cloud is a great tool, but not without its challenges.

Tips for how to get better outcomes when you clone availability in the cloud

1. Clone operational systems

This sounds obvious, but I have seen it happen more than once in real enterprise environments. If you clone your non-functional system, the clone will be equally non-functional and problematic when you restore it. Be sure that the clone you make was from an operational and functional system.

2. Sync data to disk and resync on restore

File system integrity is critical. If you don’t ensure your application and/or VM are in a consistent state, most vendors will not guarantee the resulting created image. Since snapshots only capture data that has been written to your volume at the time the snapshot command is issued, this might exclude any data that has been cached by any applications or the operating system. Making sure data has been properly synced to the file system is an important step, and absolutely critical in a cluster environment.

File system integrity is also critical to keep in mind when you restore from an image. If you are using data replication and you restore an image as source or target in the cluster, making sure the two nodes are in sync is paramount. Failing to do so may lead to file system errors on failover or switchover, or even potential data loss. Clone availability in the cloud to get the result you want.

3. Stop your instance

Many environments do not require you to stop an instance to create an image, and some, such as AWS will do the step of powering down the node before making the copy.  However, many tools and sites recommend making sure applications are stopped and file system access is properly synced to avoid damage, loss of integrity, or creating images that have trouble starting, stopping, or running installed applications.

4. Label everything in the cloud (nodes, disks, NICs,  everything)

While creating a clone is a free operation, the resulting disks and components typically are not.  AWS states, for example, that you are “charged for the snapshots until you deregister the image and delete the snapshots.”  When things aren’t labeled, knowing what is in use or not in use and why it was created can become problematic. It also becomes subjected to the fleeting memories or poor concentration of existing team members.  Label everything.

5. Prune clones and snapshots often (cost savings and headache savings)

Pruning old snapshots and clones is not only good for the cost savings, but it is also good for reducing headaches.  Older snapshots run the risk of reintroducing vulnerabilities that have been addressed or resolved in newer copies.  As VP of Customer Experience at SIOS Technology Corp., I saw the consequences firsthand when we worked with a customer who restored from a snapshot. They ran into several problems as they restarted the application. After troubleshooting, we determined that the clone was running an older version of security software. The cached credentials and metadata stored in the user profile were no longer in sync with the actual application data stored on the externally mounted data drives.

6. Limit or restrict cloning of clones in the cloud

Lastly, not everything you do in the cloud needs to be cloned. Consider limiting the types of workloads that you will clone and restrict the number or roles who can create clones in your environment.

In the movie, when Doug’s clones sparked their own series of duplications, an already overwhelmed Doug (Michael Keaton) is forced to exert extra energy to manage his many clones while trying to hide the mess he created from his wife. Achieving clone availability in the cloud with better outcomes is not difficult. Clone carefully to avoid making more work and adding risk from a tool that was supposed to make your work easier and your environment safer.

– Cassius Rhue, Vice President, Customer Experience

Reproduced from SIOS

Convert Azure Clusters To Managed Disks

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Why you should convert azure clusters to managed disks

Why You Should Convert Azure Clusters To Managed Disks

You may have heard about the recent storage outage that impacted some instances in the US East region back on March 16th. A root cause analysis of the outage is posted here. March 16th US East Storage Outage

Customer Impact

A subset of customers using Storage in the East US region may have experienced errors and timeouts while accessing their storage account in a single Storage scale unit.

You might be asking, “What is a single Storage scale unit”. Well, you can think of it as a single storage cluster, or single SAN, or however you want to think about it. I don’t think Azure publishes their exact infrastructure. Although you can probably assume that behind the scenes they are using Scale Out File Servers for backend storage.

Survive The Outage With Minimal Downtime

So the question is, how could I have survived this outage with minimal downtime? If you read further down that root cause analysis you come across this little nugget.

Virtual Machines using Managed Disks in an Availability Set would have maintained availability during this incident.

Hence, it is time to Convert Azure Clusters To Managed Disks

What’s Managed Disks?

On February 8th Corey Sanders announced the GA of Managed Disks.

Managed Disks would have helped in this outage. Because by leveraging an Availability Set combined with Managed Disks, each of the instances in your Availability Set are connected to a different “Storage scale unit”. So in this particular case, only one of the cluster nodes would have failed, leaving the remaining nodes to take over the workload.

Prior to Managed Disks being available (anything deployed before 2/8/2016), there was no way to ensure that the storage attached to your servers resided on different Storage scale units. Sure, you could use different storage accounts for each instances. But in reality that did not guarantee that those Storage Accounts provisioned storage on different Storage scale units. More reasons to Convert Azure Clusters To Managed Disks.

So while an Availability Set ensured that your instances reside in different Fault Domains and Update Domains to ensure the availability of the instance itself, the additional storage attached to each instance really represented a single point of failure. Although the storage itself is highly resilient, with three copies of your data and geo-redundant options available, in this case with a power failure the entire Storage scale unit went down along with all the servers attached to it.

So long story short… Convert Azure Clusters To Managed Disks as soon as possible in order to help minimize downtime

https://docs.microsoft.com/en-us/azure/virtual-machines/virtual-machines-windows-migrate-to-managed-disks

And if you really want to minimize downtime you should consider Hybrid Cloud Deployments that span cloud providers or on-prem to cloud!

Reproduced with permission from Clusteringformeremortals.com

Are Replicated Clusters With DataKeeper Better?

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Why Replicated Clusters With DataKeeper Are Better Than Single Copy SAN Based Clusters?

If you have followed the history of clustering as closely as I have for the past 10 years as a Microsoft Cluster MVP, you will notice that Microsoft has been steadily moving away from single copy clusters. It started with Windows Server 2003 with the elimination of a shared disk quorum and the introduction of majority node set quorums and the file share witness. The complaint with clusters based on shared disk quorums was that if the quorum became unavailable or corrupt, the entire cluster would fail. This was a major complaint and it was primarily what gave clustering a bad name in the early days.

Once the shared disk quorum was eliminated, people were still left with their application data residing on the cluster which was also a problem as the SAN was still a single point of failure in a cluster, a performance impediment and a management headache. Microsoft has begun to address those concerns with the introduction of Exchange 2007 CCR and Exchange 2010 DAGs as well as SQL Server 2008 R2 Database Mirroring. Microsoft has eliminated Exchange 2010 single copy clusters entirely and SQL Server single copy clusters are only still around because they haven’t perfected SQL Server replication yet.

The Introduction of SIOS DataKeeper

Hyper-V is the most recent cluster resource supported by Microsoft clustering that does not yet have a native cluster integrated replication solution. This is where SIOS DataKeeper fits in. We first demonstrated our DataKeeper Hyper-V replication solution at the Microsoft Virtualization launch in September of 2008 and have been providing HA and DR solutions for Hyper-V since Hyper-V was first introduced. Our solution is logo certified for Windows Server 2008 R2 as well as Hyper-V.

Why DataKeeper?

DataKeeper fills the gap left by single copy clusters as shown in the table below and subsequent paragraphs. The following customer story also highlights some of the reasons why people are adopting DataKeeper in lieu of SAN based solutions.

http://www.computerweekly.com/news/2240177361/University-shuns-HP-array-features-for-SIOS-host-based-replication

Are Replicated Clusters With DataKeeper Better?

Eliminates single point of failure

A SAN is a single entity made up of redundant pieces. To have a truly redundant SAN you need redundant controllers, power supplies, CPU’s, switches, UPS, RAM and the clients connecting to it need to have redundant NICs or HBAs and multi-path solutions configured. Even once you have eliminated hardware as a single point of failure, the SAN is still controlled by firmware which itself is a single point of failure. And then because the SAN resides in a single location, any physical disasters (think water, fire, etc.) also represents a risk.

I/O Performance

Given same disk specs, disk installed locally will perform better than disks stored on a SAN accessed via iSCSI. Also, using local storage opens up the possibility of using even higher speed storage solutions such as flash based PCIe storage which outperforms SANs that costs hundreds of thousands of dollars at a fraction of the costs.

Cost

Not only do you have to factor in the initial investment, which the DataKeeper solution wins by a significant percentage, you have to factor in the ongoing expense involved with maintenance, power and cooling required for any enterprise class SAN.

Supports future expansion for Disaster Recovery

Should disaster recovery solutions become a requirement in the future the DataKeeper solution can easily accommodate adding an addition Hyper-V node in a remote location in a multisite cluster configuration for a robust disaster recovery solution that includes the best RTO and RPO available. The SAN solution would require the purchase of an additional SAN, replication software and might not even include cluster integration as there are only a few solutions that actually integrate with failover clustering as well as DataKeeper does.

Eliminates Planned Downtime

With SAN based cluster solutions, any maintenance on the SAN requires planned downtime. The DataKeeper solution allows for rolling upgrades, meaning planned downtime for hardware maintenance is eliminated.

Eases management

SAN administration usually involves a SAN administrator who is familiar with the features and functionality of a SAN. The DataKeeper solution on the other hand is a simple software solution that is managed by the Windows Server administrator and features complete integration with Windows Server Failover Clustering, meaning the management is controlled through failover cluster, a tool which should be familiar with most Windows Administrators.

Summary

In summary, DataKeeper is able to provide a much more resilient cluster solution at a fraction of the cost of SAN based solutions.

SQL Server 2012 Multi-site Failover Cluster For Disaster Recovery

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SQL Server 2012 Multi-site Failover Cluster for Disaster Recovery using SteelEye DataKeeper Cluster Edition

Microsoft just released a great white paper on new support for SQL Server 2012 Multi-site Failover Cluster for Disaster Recovery. If you’re interested, you can download a copy here.

In fact, don’t forget that I blogged about this feature back in an earlier post. I included a video demonstration. It shows a SQL Server 2012 multisite failover cluster for disaster recovery using SteelEye DataKeeper Cluster Edition. SQL Server 2012 and cross subnet failover capabilities will open up a whole new world of possibilities for people looking for disaster recovery options.

Reproduced with permission from https://clusteringformeremortals.com/2012/01/03/sql-server-2012-disaster-recovery-multisite-clusters/