|By Peter Velikin||
|March 7, 2012 07:30 AM EST||
Whether ‘tis nobler in the mind to suffer the slings and arrows of your IT manager or to take up cache against a sea of data. With apologies to Bill Shakespeare, the IT Dog is discussing two different cache write policies: write through and write back. Let me take a run at telling you what they are, why they are different and what you need to think about when you decide what policy to use.
Cache Write Through
This is the easier to explain and understand of the two policies discussed here. Cache write through is like having your cake and eating it too. Data is written into cache for fast retrieval when needed for a future operation and at the same time, the data is written into the underlying memory location (think central database or primary storage here). Why is cache write through good? Because it insures the integrity of the data in the database so if another application needs to access the same data, you can be sure the data in the database is correct or ‘fresh’. Another benefit to cache write through is there is always a good, reliable copy of the data in the database if something happens to the cache itself (e.g. power failure). “So Dog, why wouldn’t I do cache write through all the time?” Well, because cache write through has a little problem in that the writing application must wait for the completion of the write into the primary storage before it can proceed with the next operation and as you well know, writing to primary storage can be slow which is why you are using cache in the first place. Write through cache can therefore slow down the application. So you get data integrity and assurance at the expense of application speed.
Getting Down And Dirty
We need to get a little dirty here to explain cache write back. No, not that kind of dirty; we are still talking about data and applications here. Cache write back uses cache as the temporary storage for the ‘freshest’ data and that same data is updated in the primary storage at a later time. This means that when a data location is updated, it is written to only to cache, not to primary storage and the data in cache is termed ‘fresh’. The corresponding data location in primary storage now does not match the ‘fresh’ cache data and is now considered ‘stale’. The cache controller keeps track of the state of the primary storage (fresh or stale) by using a ‘dirty’ bit to indicate if the data in the primary storage matches the cache data copy or does not. If a request for the stale data from primary storage comes in from another application, then the controller has to update the primary storage location before the application can use the data. “Why would I use this cache policy?” Well, because data is not written into slower, primary storage each time it is updated, the writing application does not have to wait for the write to primary storage to be completed before moving on to the next operation so the application runs faster. The problem with this policy is there is a small chance that the fresh cache data (or the dirty bit) can be corrupted before the data is written into primary storage. So you get speed at the expense of possible loss of data integrity.
What To Do When?
The question on which of these two cache policies to use depends on the application. Applications that absolutely cannot risk data loss (banks storing real-time trading info, continuous data protection in back store) should use write through cache policy and applications that can tolerate data loss (back end, analytics, etc.) can speed performance by using write back cache policy.
Tell Me What Your Policy Is
Let me know if you have experience with using either write back or write through cache policy and what you have learned from deploying that technique.
Bit6 today issued a challenge to the technology community implementing Web Real Time Communication (WebRTC). To leap beyond WebRTC’s significant limitations and fully leverage its underlying value to accelerate innovation, application developers need to consider the entire communications ecosystem.
Nov. 24, 2014 09:30 AM EST Reads: 1,233
Cloud Expo 2014 TV commercials will feature @ThingsExpo, which was launched in June, 2014 at New York City's Javits Center as the largest 'Internet of Things' event in the world.
Nov. 24, 2014 09:00 AM EST Reads: 1,475
SYS-CON Events announced today that Windstream, a leading provider of advanced network and cloud communications, has been named “Silver Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9–11, 2015, at the Javits Center in New York, NY. Windstream (Nasdaq: WIN), a FORTUNE 500 and S&P 500 company, is a leading provider of advanced network communications, including cloud computing and managed services, to businesses nationwide. The company also offers broadband, phone and digital TV services to consumers primarily in rural areas.
Nov. 23, 2014 07:30 PM EST Reads: 1,709
"There is a natural synchronization between the business models, the IoT is there to support ,” explained Brendan O'Brien, Co-founder and Chief Architect of Aria Systems, in this SYS-CON.tv interview at the 15th International Cloud Expo®, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Nov. 23, 2014 12:00 PM EST Reads: 1,644
The major cloud platforms defy a simple, side-by-side analysis. Each of the major IaaS public-cloud platforms offers their own unique strengths and functionality. Options for on-site private cloud are diverse as well, and must be designed and deployed while taking existing legacy architecture and infrastructure into account. Then the reality is that most enterprises are embarking on a hybrid cloud strategy and programs. In this Power Panel at 15th Cloud Expo (http://www.CloudComputingExpo.com), moderated by Ashar Baig, Research Director, Cloud, at Gigaom Research, Nate Gordon, Director of T...
Nov. 23, 2014 07:45 AM EST Reads: 1,480
The definition of IoT is not new, in fact it’s been around for over a decade. What has changed is the public's awareness that the technology we use on a daily basis has caught up on the vision of an always on, always connected world. If you look into the details of what comprises the IoT, you’ll see that it includes everything from cloud computing, Big Data analytics, “Things,” Web communication, applications, network, storage, etc. It is essentially including everything connected online from hardware to software, or as we like to say, it’s an Internet of many different things. The difference ...
Nov. 22, 2014 10:00 PM EST Reads: 1,418
ARMONK, N.Y., Nov. 20, 2014 /PRNewswire/ -- IBM (NYSE: IBM) today announced that it is bringing a greater level of control, security and flexibility to cloud-based application development and delivery with a single-tenant version of Bluemix, IBM's platform-as-a-service. The new platform enables developers to build ap...
Nov. 22, 2014 05:30 PM EST Reads: 1,475
An entirely new security model is needed for the Internet of Things, or is it? Can we save some old and tested controls for this new and different environment? In his session at @ThingsExpo, New York's at the Javits Center, Davi Ottenheimer, EMC Senior Director of Trust, reviewed hands-on lessons with IoT devices and reveal a new risk balance you might not expect. Davi Ottenheimer, EMC Senior Director of Trust, has more than nineteen years' experience managing global security operations and assessments, including a decade of leading incident response and digital forensics. He is co-author of t...
Nov. 22, 2014 05:30 PM EST Reads: 1,327
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at Internet of @ThingsExpo, James Kirkland, Chief Architect for the Internet of Things and Intelligent Systems at Red Hat, described how to revolutioniz...
Nov. 21, 2014 09:15 PM EST Reads: 1,395
Technology is enabling a new approach to collecting and using data. This approach, commonly referred to as the "Internet of Things" (IoT), enables businesses to use real-time data from all sorts of things including machines, devices and sensors to make better decisions, improve customer service, and lower the risk in the creation of new revenue opportunities. In his General Session at Internet of @ThingsExpo, Dave Wagstaff, Vice President and Chief Architect at BSQUARE Corporation, discuss the real benefits to focus on, how to understand the requirements of a successful solution, the flow of ...
Nov. 21, 2014 08:00 PM EST Reads: 1,455
The security devil is always in the details of the attack: the ones you've endured, the ones you prepare yourself to fend off, and the ones that, you fear, will catch you completely unaware and defenseless. The Internet of Things (IoT) is nothing if not an endless proliferation of details. It's the vision of a world in which continuous Internet connectivity and addressability is embedded into a growing range of human artifacts, into the natural world, and even into our smartphones, appliances, and physical persons. In the IoT vision, every new "thing" - sensor, actuator, data source, data con...
Nov. 21, 2014 08:00 PM EST Reads: 1,403
"BSQUARE is in the business of selling software solutions for smart connected devices. It's obvious that IoT has moved from being a technology to being a fundamental part of business, and in the last 18 months people have said let's figure out how to do it and let's put some focus on it, " explained Dave Wagstaff, VP & Chief Architect, at BSQUARE Corporation, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Nov. 21, 2014 07:00 PM EST Reads: 1,307
Focused on this fast-growing market’s needs, Vitesse Semiconductor Corporation (Nasdaq: VTSS), a leading provider of IC solutions to advance "Ethernet Everywhere" in Carrier, Enterprise and Internet of Things (IoT) networks, introduced its IStaX™ software (VSC6815SDK), a robust protocol stack to simplify deployment and management of Industrial-IoT network applications such as Industrial Ethernet switching, surveillance, video distribution, LCD signage, intelligent sensors, and metering equipment. Leveraging technologies proven in the Carrier and Enterprise markets, IStaX is designed to work ac...
Nov. 20, 2014 09:15 PM EST Reads: 1,385
C-Labs LLC, a leading provider of remote and mobile access for the Internet of Things (IoT), announced the appointment of John Traynor to the position of chief operating officer. Previously a strategic advisor to the firm, Mr. Traynor will now oversee sales, marketing, finance, and operations. Mr. Traynor is based out of the C-Labs office in Redmond, Washington. He reports to Chris Muench, Chief Executive Officer. Mr. Traynor brings valuable business leadership and technology industry expertise to C-Labs. With over 30 years' experience in the high-tech sector, John Traynor has held numerous...
Nov. 20, 2014 06:00 PM EST Reads: 1,345
The 3rd International @ThingsExpo, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that it is now accepting Keynote Proposals. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - computers, smartphones, tablets, and sensors - connected to the Internet by 2020. This number will continue to grow at a rapid pace for the next several decades.
Nov. 20, 2014 01:00 PM EST Reads: 1,592
The Internet of Things is not new. Historically, smart businesses have used its basic concept of leveraging data to drive better decision making and have capitalized on those insights to realize additional revenue opportunities. So, what has changed to make the Internet of Things one of the hottest topics in tech? In his session at @ThingsExpo, Chris Gray, Director, Embedded and Internet of Things, discussed the underlying factors that are driving the economics of intelligent systems. Discover how hardware commoditization, the ubiquitous nature of connectivity, and the emergence of Big Data a...
Nov. 20, 2014 12:30 PM EST Reads: 1,800
Almost everyone sees the potential of Internet of Things but how can businesses truly unlock that potential. The key will be in the ability to discover business insight in the midst of an ocean of Big Data generated from billions of embedded devices via Systems of Discover. Businesses will also need to ensure that they can sustain that insight by leveraging the cloud for global reach, scale and elasticity.
Nov. 18, 2014 09:00 PM EST Reads: 2,019
SYS-CON Events announced today that IDenticard will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. IDenticard™ is the security division of Brady Corp (NYSE: BRC), a $1.5 billion manufacturer of identification products. We have small-company values with the strength and stability of a major corporation. IDenticard offers local sales, support and service to our customers across the United States and Canada. Our partner network encompasses some 300 of the world's leading systems integrators and security s...
Nov. 18, 2014 08:15 PM EST Reads: 1,581
IoT is still a vague buzzword for many people. In his session at @ThingsExpo, Mike Kavis, Vice President & Principal Cloud Architect at Cloud Technology Partners, discussed the business value of IoT that goes far beyond the general public's perception that IoT is all about wearables and home consumer services. He also discussed how IoT is perceived by investors and how venture capitalist access this space. Other topics discussed were barriers to success, what is new, what is old, and what the future may hold. Mike Kavis is Vice President & Principal Cloud Architect at Cloud Technology Pa...
Nov. 18, 2014 01:30 PM EST Reads: 2,016
Cloud Expo 2014 TV commercials will feature @ThingsExpo, which was launched in June, 2014 at New York City's Javits Center as the largest 'Internet of Things' event in the world. The next @ThingsExpo will take place November 4-6, 2014, at the Santa Clara Convention Center, in Santa Clara, California. Since its launch in 2008, Cloud Expo TV commercials have been aired and CNBC, Fox News Network, and Bloomberg TV. Please enjoy our 2014 commercial.
Nov. 13, 2014 05:00 AM EST Reads: 3,548