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What if a software error corrupts a vital file on your computer? What if your office catches fire, taking your servers with it?

What if you suffer a catastrophic hardware failure and lose all your data? What if your ISP has technical issues, and you lose Internet access for a few days?

It’s safe to say that these are all uncommon, extremely undesirable outcomes. But it’s important to prepare for any possible eventuality, no matter how unlikely, so that service doesn’t get disrupted.

The way we do that is with something called ‘redundancy’.

What’s the Difference Between Backups and Redundancy?

Redundancy is frequently confused with backups 6 Safest Ways to Backup & Restore Your Files in Windows 7 & 8 6 Safest Ways to Backup & Restore Your Files in Windows 7 & 8 By now, we're sure you've read the advice over and over: Everyone needs to back up their files. But deciding to back up your files is only part of the process. There are so many... Read More . Indeed, the concepts are relatively similar, albeit with some important differences.

Whilst ‘backup’ is commonly about creating copies of data Turn Your NAS Or Windows Share Into A Time Machine Backup Turn Your NAS Or Windows Share Into A Time Machine Backup Use your NAS, or any network share, for backing up your Mac with Time Machine. Read More in preparation for a catastrophic loss, redundancy refers to more than just data storage. It focuses more on the ability to provide a continuity of service, no matter what happens. In terms of data, it’s done by ensuring that data is stored in multiple, disparate locations.

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redundancy-drives

There’s also network redundancy, where a network is configured with multiple alternate systems to ensure that no matter what happens, there’s still a continuity of service.

So, how does it work in the real world? Let’s find out, starting with data redundancy.

Data Redundancy

Everyone – businesses and end-users – have quite rapidly become incredibly data driven and computerized. For businesses and companies, everything they know about their customers and clients is recorded, stored, and recalled from computers, to the point where any loss or disruption can be disastrous.

Indeed, according to the National Archives and Records Administration, 93% of all companies that lose access to their data center for 10 days or more ultimately go bankrupt within one year. For businesses, data redundancy isn’t optional. It’s a mandatory, essential business expense.

redundancy-drive-days

It’s vital that should data be lost or corrupted, it becomes possible to reconstruct or recover it as quickly as possible, and resume normal service.

There are a number of ways businesses ensure data redundancy. Each come with their own advantages, in terms of speed, cost-effectiveness, and management.

Perhaps the most basic form of data-redundancy is off-site tape backups. Here, a complete bit-for-bit copy of a storage volume is taken and stored on reels of magnetic tape. These are then collected and moved to an off-site storage facility, where they can easily be retrieved in the case of a catastrophic failure.

Magnetic Tapes Are Still Around

Magnetic tape is an incredibly old data storage technology From Punch Cards to Holograms - A Short History of Data Storage From Punch Cards to Holograms - A Short History of Data Storage Let's take a look at some of the technologies that shaped modern data storage, as well as where we go from here. Read More , but one that’s still has its place today. Not only is it highly cost-effective, but magnetic tape can store incredible amounts of data. Sony, for example, has built a magnetic tape technology which can theoretically store up to 185 TB of data. Above all, magnetic tape works no matter how fast your network connection is.

redundancy-storage-disk

Cloud Backups

Another popular approach at ensuring data redundancy is with versioned, online or cloud backups NAS vs the Cloud: Which Remote Storage Is Right for You? NAS vs the Cloud: Which Remote Storage Is Right for You? Network Attached Storage (NAS) straddles the line between a local hard drive and cloud storage, and gives you the benefits of both. Read More . The online storage sphere is one that’s becoming increasingly crowded, with offerings from Google, Microsoft and Rackspace. Despite that, there’s only one service that’s worth talking about – Amazon Web Services’s Simple Storage Service (S3).

Amazon S3 allows you to cheaply, quickly and easily save your data to the cloud. It’s a service that has a number of potential applications 4 Great Uses for Amazon's S3 Web Services 4 Great Uses for Amazon's S3 Web Services Despite Amazon being most well known for their retail services, they actually offer a host of web services for developers and home users that take advantage of Amazons experience and scalability with massive amounts of... Read More , and one that’s increasingly being used by companies aiming to affordably store off-site backups.

Thankfully, it’s a task that Amazon’s S3 has managed to excel at. That’s largely due to the fact they’ve got an incredibly attractive pricing model. Instead of charging a flat fee, like other cloud storage providers, customers are charged by the gigabyte. They also have a compelling service level agreement, where they guarantee a near-perfect availability and reliability.

How Amazon Web Services works at a low-level is still somewhat of a mystery. But what we do know is they have data centers in almost every single continent, and all of their servers are configured to be highly redundant, with data stored across multiple systems. This ensures that even if a machine fails in an Amazon data center, your data is safe.

But no matter how you store your redundant data – be that with tape, the cloud, or (not recommended) on a flash drive buried under your garden – the point remains the same. Important data must be duplicated, and kept on a separate storage medium, where it can be easily accessed in case of emergency.

Later, we’ll talk about how you can use data redundancy at home, with an emphasis on RAID. Until then, let’s talk about network redundancy.

Network Redundancy

The network infrastructure we all use on a daily basis is incredibly fragile. It’s all too easy for a freak accident – like someone driving their car into a FTTC cabinet, or a router burning out – to result in a prolonged period of network downtime.

redundancy-fttc

Businesses mitigate against this by ensuring that their networks have adequate redundancy to cope in the case of an emergency.

At its most basic level, this means ensuring that no one failure can take down a network. This is accomplished by having multiple network devices What Is Multihoming and What Do You Need to Set It Up? What Is Multihoming and What Do You Need to Set It Up? Here we will introduce you to multihoming, show you where and why you may want to use it, and how you can set it up. Read More (like routers, switches and hubs) that are configured to take over when one fails.

There’s also ISP redundancy. Here, a network gateway is connected to two separate ISPs, with one taking over should the other fail. Whilst both ISPs are functioning normally, traffic can be shared between the two of them, reducing network congestion. This is commonly known as load sharing.

Later, we’ll talk about practical ways you can add network redundancy to your home.

Redundancy At Home

At this point, we’ve talked extensively about redundancy within the context of how businesses operate. But what about ordinary home users?

First, let’s talk about data redundancy. Many of the options available to businesses are also available to regular consumers. Take, for example, Amazon S3. For their standard pricing tier, they charge $0.03 per gigabyte under 1 terabyte. To put that in context, that’s about $3 per month to store 100 gigabytes.

redundancy-s3-pricing

Amazon S3 can also be easily accessed and controlled from the dedicated OS X, Windows and Linux applications.

If you’re looking for data redundancy without having to store your files elsewhere, you can also build a RAID array or a network attached storage.

What’s RAID?

The acronym RAID stands for “redundant array of inexpensive disks”, and works by combining multiple hard drives into a single logical unit. This has the advantage of providing data redundancy and improved access times. There are many different types of RAID array, each with their own advantages and disadvantages. James Bruce previously published an article explaining RAID storage and how it works What Is RAID Storage & Can I Use It On My Home PC? [Technology Explained] What Is RAID Storage & Can I Use It On My Home PC? [Technology Explained] RAID is an acronym for Redundant Array of Independent Disks, and it’s a core feature of server hardware that ensures data integrity. It’s also just a fancy word for two or more hard disks connected... Read More .

redundancy-raid-drives

The biggest advantage of RAID is that should one drive fail, no data is lost due to the redundancy. Since two or more drives are required for a RAID setup, the remaining drives run the show. The damaged drive should be replaced to keep the RAID array going.

So, what about network redundancy? Admittedly, this is something that companies spend thousands setting up.

It’s also something that large corporate networks lend themselves favorably to, due to their massive size. Whereas, home networks tend to be significantly smaller, and provide less opportunities for establishing redundancy.

With that in mind, you’re probably better of just replacing a component when it fails, rather than take the effort to manually configure a redundant router.

However, you can ensure you’re never without an Internet connection by purchasing a mobile WiFi hotspot 3 Foolproof Ways to Create Your Own Portable Wi-Fi Hotspot for Tethering in North America 3 Foolproof Ways to Create Your Own Portable Wi-Fi Hotspot for Tethering in North America Do you want to give multiple wireless gadgets on-the-go internet access? Are you sick of getting ripped off by wireless hotspot tethering? There’s a variety of technologies that can help you – the two most... Read More , or by ensuring you can tether your phone Tethering: How To Use Mobile Internet On Your PC Tethering: How To Use Mobile Internet On Your PC Want to share your phone's data connection with your computer? Here's exactly how to do it, how fast you can expect it to be, and how it will affect your battery life. Read More to your laptop.

Avoiding SPOFF

The acronym SPOFF stands for “Single Point Of Failure”. It means that should one part of a system fail, the entire system becomes rendered unusable. This is, of course, incredibly undesirable. The way we avoid creating a SPOFF is through redundancy. By ensuring no one thing can stop a system from working properly.

Do you have a story of building a redundant system? Got a cool story of how you ensured continuity of service? I’d like to hear it. Leave me a comment below.

Photo Credits: Preparing hard drives for the home network, Magnetic Storage Disk, Not on Broadband, Five Day’s Backup, IMG_1265

  1. Chris Rodinis
    August 12, 2015 at 4:51 pm

    Great Article Thanks!

    • Matthew Hughes
      August 17, 2015 at 8:17 pm

      Thanks for reading! :)

  2. Bakhram Askerov
    August 12, 2015 at 4:06 am

    I would mention what is probably the most used cloud backup/redundancy (yes, it can be used as both) service - ShareFile from Citrix. It isn't cheap, but from the Business Continuity point of view, it's a lot cheaper, better and more flexible, than a typical off-site data replication. We just started using it at our firm and we love it!

    • Matthew Hughes
      August 17, 2015 at 8:18 pm

      Is Sharefile the most used? In the UK, we tend to stick to AWS and Rackspace.

  3. julian thibeault
    August 11, 2015 at 3:53 am

    There is another entire section that this article is not diving into: Business continuity. This is the ability to prevent downtime altogether. Something like Veeam, Axcient or Datto offer solutions that will create virtual copies of your servers and keep them running for optimal redundancy.

    Otherwise, this article has some great basic information for uninformed masses.

    • Matthew Hughes
      August 17, 2015 at 8:18 pm

      That's another article in itself! :)

  4. hildyblog
    August 6, 2015 at 8:19 pm

    I learned the hard way that motherboards can fail and that to recover my RAID 0 (striped - no redundancy - bad idea) data I had to find the same motherboard or purchase recovery software.

    Question - do all/some/none of the personal NAS solutions use proprietary formats for mirrored (RAID 1) drives. In other words, if the NAS fails can I pull a drive and read it on any computer?

    • likefun butnot
      August 7, 2015 at 5:40 am

      The answer is essentially that it depends on the NAS. Most of them are running some UNIX variant under the hood and others might be implementing iSCSI or the like so that the NAS storage is entirely under control of the Initiator. In any case, your best best for access of a single disk from a dedicated NAS unit is probably a Linux machine rather than Windows or OSX. If you want to recover a RAID array from a NAS, you're probably going to want/need a crash course on Linux LVM and a lot of patience.

      No storage system is foolproof. The more important the data is, the more different ways it should be stored.

  5. likefun butnot
    August 6, 2015 at 8:02 pm

    The storage server in my back bedroom has just under 100TB of addressable storage (around 160TB when counting parity and caching disks). Nothing else besides tape made sense for my backup needs. I managed to score an LTO4 changer from Craigslist a few years ago. Tape is a hassle. It's a pain to store and sometimes the tapes do go bad. But nothing works better and nothing would get my data back more quickly if I had an issue.

    I use several RAID6 arrays of 18 - 20TB worth of disks. RAID5 is provably dangerous for arrays larger than approximately 12TB because of the hard error rate on modern hard drives; it's simply mathematically impossible for there to NOT be a single unrecoverable error on one of the member drives, meaning that a situation where operating from parity information will lead to data loss is a certainty rather than merely a possibility. RAID6 likewise becomes untenable at around ~30TB volumes. I'm surprised the author didn't mention this aspect to RAID since it's an increasingly serious limitation of the technology.

    I run a ~150Mbit wireless link from my home to an off-site office that happens to be just down the street from my place. I located one of my old storage servers there that can handle about 40TB of redundant data. Data synchronizes reasonably well over Windows DFS.

    I use Crashplan Pro to back up my personal, non-bulk data and my home storage server is a Crashplan target for other systems I manage.

    I find this all works very well, although my ISP and anyone else who happens to be on the same cable segment or wireless spectra I'm using probably hate me.

    Yes, this is all being done on a level well outside what normal humans have in their homes, but for me it's the logical outcome of wanting to keep tens of terabytes of data highly available.

  6. prittman
    August 6, 2015 at 4:26 pm

    I keep a backup copy of my entire hard drive, that I make every month. That way, in case I lose my laptop, I can restore everything up to the last month. The most crucial file that I work on is emailed to myself in the middle of the month (2 weeks before & then 2 weeks after my hard drive is backed up). If you dont have that much data to back up, you could put it on 2 or 3 DVDs.

    In case my house burns down, I keep what I call my "drop dead" files (files that I would consider suicide over, if I were to lose them---j/k) backed up on amazon cloud service. They arent the best but they arent bad either (in terms of price and ease of recovery). Amazon charges $50 a year for this, and others are right at that price.

    Now of course, if my house burns down AND the internet is permanently taken down as well, at the same time, then Im screwed.

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