A server apocalypse can come in different shapes and sizes. Be prepared

Plan Bs, from corrupted data to pandemics


I run into the same misconceptions about business continuity on an almost daily basis. “We’ve already got backups, so why would we need to have a disaster recovery site as well?,” comes up with alarming regularity, as does: “We spent tens of thousands on a disaster recovery site, so why did we have that four-minute outage – why didn’t we switch over to DR and get our money’s worth?”

It’s nobody’s fault, really. For all the efforts of technical folk to explain and educate, and the efforts of the business to listen and learn, it’s easy to see why it can get confusing and ultimately lost in translation.

A lot of the terminology is the same (or at least, very similar) and the same words might mean different things, depending on who says them and in what context.

Backups

The fundamental principle of the backup is straightforward. A backup is a copy of a fixed point in time, to which you can return in the event of an issue.

An application or system has a snapshot of its current state written out to a storage, and that is retained for use in case of emergency. That might be a copy of an application or files, or it could be something more complex like a set of databases or an entire server, but the key facts remain: you need somewhere to store it, and you need somewhere to restore it.

Whether you’re writing backups regularly on a schedule, or taking them manually prior to making changes, you’ll want to keep it somewhere safe. For short-term use that’s probably onto disk, but for long-term retention that might be onto tape or other media.

Then something happens, and that means your backups are required. Perhaps data gets corrupted or lost, and you need to wind the clock back. Maybe a server has died, and you need to perform a bare-metal restore.

Whatever the case, you’ll be restoring your backups onto a server or system, and it is for this reason that backups alone simply aren’t enough as a method of business continuity. It also takes time, and lots of it.

You can have the most rigorous backups in the world, but if you don’t have somewhere to restore them (i.e. a disaster recovery site) then you may as well not have them at all.

Redundancy

Redundancy is a relatively straightforward concept. Servers have redundant power supplies, to ensure constant delivery in the event of a failure. Further up the chain, you’ll want to be feeding your redundant power supplies from diverse power feeds in case one fails; as another layer of redundancy.

Your power will be protected by uninterruptible power supplies and generators, and – you guessed it – you’ll want to have more than one of each of these to ensure continued power delivery in the event of a failure.

You’ve probably heard of components like generators being referred to as having N+1 or 2N coverage, and these are measures of redundancy. In an N+1 scenario, for each component (N) you would always maintain one more in case of failure: if you have one generator, then you must always have a second spare; if your core number of generators increases to three, then you must always have a fourth available.

In 2N, you would always have the same number of components again: with one generator, then you would still only have one spare; but with three core generators you would have three spare for redundancy, giving a total of six generators.

It’s worth mentioning that redundancy is not always an instantaneous process. In some instances (such as server power supplies or UPS systems) the redundant components will already be operating at all times, and the failover capacity is maintained within the total headroom of the operating hardware.

In the case of generators, your redundant devices will likely not be running and may take a little time to start up – it is for this reason that generators have warm oil pumped through their system even when switched off, to reduce startup delay in case they are suddenly required.

Next page: High Availability

Similar topics


Other stories you might like

  • Experts: AI should be recognized as inventors in patent law
    Plus: Police release deepfake of murdered teen in cold case, and more

    In-brief Governments around the world should pass intellectual property laws that grant rights to AI systems, two academics at the University of New South Wales in Australia argued.

    Alexandra George, and Toby Walsh, professors of law and AI, respectively, believe failing to recognize machines as inventors could have long-lasting impacts on economies and societies. 

    "If courts and governments decide that AI-made inventions cannot be patented, the implications could be huge," they wrote in a comment article published in Nature. "Funders and businesses would be less incentivized to pursue useful research using AI inventors when a return on their investment could be limited. Society could miss out on the development of worthwhile and life-saving inventions."

    Continue reading
  • Declassified and released: More secret files on US govt's emergency doomsday powers
    Nuke incoming? Quick break out the plans for rationing, censorship, property seizures, and more

    More papers describing the orders and messages the US President can issue in the event of apocalyptic crises, such as a devastating nuclear attack, have been declassified and released for all to see.

    These government files are part of a larger collection of records that discuss the nature, reach, and use of secret Presidential Emergency Action Documents: these are executive orders, announcements, and statements to Congress that are all ready to sign and send out as soon as a doomsday scenario occurs. PEADs are supposed to give America's commander-in-chief immediate extraordinary powers to overcome extraordinary events.

    PEADs have never been declassified or revealed before. They remain hush-hush, and their exact details are not publicly known.

    Continue reading
  • Stolen university credentials up for sale by Russian crooks, FBI warns
    Forget dark-web souks, thousands of these are already being traded on public bazaars

    Russian crooks are selling network credentials and virtual private network access for a "multitude" of US universities and colleges on criminal marketplaces, according to the FBI.

    According to a warning issued on Thursday, these stolen credentials sell for thousands of dollars on both dark web and public internet forums, and could lead to subsequent cyberattacks against individual employees or the schools themselves.

    "The exposure of usernames and passwords can lead to brute force credential stuffing computer network attacks, whereby attackers attempt logins across various internet sites or exploit them for subsequent cyber attacks as criminal actors take advantage of users recycling the same credentials across multiple accounts, internet sites, and services," the Feds' alert [PDF] said.

    Continue reading

Biting the hand that feeds IT © 1998–2022