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  • SharePoint Content Database Sizing

    - by Sahil Malik
    SharePoint, WCF and Azure Trainings: more information SharePoint stores majority of its content in SQL Server databases. Many of these databases are concerned with the overall configuration of the system, or managed services support. However, a majority of these databases are those that accept uploaded content, or collaborative content. These databases need to be sized with various factors in mind, such as, Ability to backup/restore the content quickly, thereby allowing for quicker SLAs and isolation in event of database failure. SharePoint as a system avoids SQL transactions in many instances. It does so to avoid locks, but does so at the cost of resultant orphan data or possible data corruption. Larger databases are known to have more orphan items than smaller ones. Also smaller databases keep the problems isolated. As a result, it is very important for any project to estimate content database base sizing estimation. This is especially important in collaborative document centric projects. Not doing this upfront planning can Read full article ....

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  • Why should we use low level languages if a high level one like python can do almost everything? [closed]

    - by killown
    I know python is not suitable for things like microcontrolers, make drivers etc, but besides that, you can do everything using python, companys get stuck with speed optimizations for real hard time system but does forget other factors which one you can just upgrade your hardware for speed proposes in order to get your python program fit in it, if you think how much cust can the company have to maintain a system written in C, the comparison is like that: for example: 10 programmers to mantain a system written in c and just one programmer to mantain a system written in python, with python you can buy some better hardware to fit your python program, I think that low level languages tend to get more cost, since programmers aren't so cheaply than a hardware upgrade, then, this is my point, why should a system be written in c instead of python?

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  • Mobile Developer Economics: Calling all Developers!

    - by Jacob Lehrbaum
    VisionMobile is currently soliciting feedback for the second edition of their popular Mobile Developer Economics report.  With the 2011 edition, VisionMobile is hoping to: "see how the dynamics of the developer world have changed since early 2010 and to provide more insights into app marketing, monetization and many other factors."If you have a couple of minutes, please check out the survey and provide your input.  In addition please help us spread the word to make sure that Java developers are well represented in this survey.  Thanks!

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  • How important is to sacriface your free time for accomplishing goals? [closed]

    - by Darf Zon
    I was reading a book about XP programming and about agile teams. While I was reading, I saw this scenario. I've never worked with a development team (just in school). So I would like what do you opine on this situation: Your boss has asked you to deliver software in a time that can only be possible to meet the project team asking if you want to work overtime without pay. All team members have young children. Discuss whether it should accept this request from your boss or should persuade the team to give their time to the organization rather than their families. What could be significant factors in the decision? As a programmer, you are offered an upgrade as project manager, but his feeling is that you can have a more effective contribution in a technical role in one administrative. Write when you should accept that promotion. Somethimes, I sacrifice my free time for accomplishing hits at work, so it's very important to me to know your opinion base of your experience.

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  • What is the role of web hosting in SEO [closed]

    - by Vinay
    Possible Duplicate: Does changing web hosting server affects SEO page ranking? SEO Geolocation What are the best ways to increase a site's position in Google? How to find web hosting that meets my requirements? I have read somewhere that hosting providers do play a role in website SEO, As my website is hosted in yahoo small business, That has got analytics and some other tool they provide to check the keyword activity, I think these can be achieved with the google's analytics as well, Server performance and Uptime is one important factor. I have also got few doubts in my mind 1) Does shared hosting affect the SEO and what is the role of domain extension like .com, .in, .org ,etc. 2) Does server geolocation affects the SEO 3) Does server OS affects the SEO. Apart from the above, Is there any factors that affect the SEO One more last question that If hosting really matters lot, can you suggest me a web hosting service for a small business e commerce site for PHP

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  • deciphering columnar transposition cipher

    - by Arfan M
    I am looking for an idea on how to decipher a columnar transposition cipher without knowing the key or the length of the key. When I take the cipher text as input to my algorithm I will guess the length of the key to be the factors of the length of the cipher text. I will take the first factor suppose the length was 20 letters so I will take 2*10 (2 rows and 10 columns). Now I want to arrange the cipher text in the columns and read it row wise to see if there is any word forming and match it with a dictionary if it is something sensible. If it matches the dictionary then it means it is in correct order or else I want to know how to make other combinations of the columns and read the string again row wise. Please suggest another approach that is more efficient.

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  • Help comparing Cocos2d and Unity3d for this project.....

    - by Omega
    I will not go into details, but I would like to hear your opinions about this: Essentially, my project will be a 2d game, with lots of complex levels, where some might be simple and others might be a bit more deep, with physics, etc. We want to implement our very own online structure: logging in, leaderboards, achievements, friends etc with our own servers. This means no OpenFeint nor GameCenter at all. We expect this game to be very large in both graphics and audio. We wish to use in-app purchases. Now, we considered two options. Cocos2d and Unity3d. We need help deciding using the factors I mentioned before (networking, good performance even for a large game in terms of graphics and audio like this, in-app purchases, etc) which option would fit better this? Technically, both options can create 2d games. I'd like to hear your opinion.

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  • Determining Cost of API Calls

    - by Sam
    [This is a cross-post originally posted by me in SO. I think the question is more appropriate here.] I was going through the adwords API and came across their rate sheet - http://code.google.com/apis/adwords/docs/ratesheet.html . They charge $0.25 per 1000 API units and under the 'Operation Costs' sections list the cost (in API units) of different API calls. I am curious - based on what factors do they (and others API developers) calculate the cost of an API call? Is there any simple formula or a standard way to determine this? Note: When I say 'cost' of an API call, I don't mean the money but the API units. For example, how do you determine one API call costs 100 'units' and another 1000?

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  • How to diagnose a search engine ranking drop?

    - by Itai
    EDIT: Reworded & Cleaned Up to Ease Understanding There has been a significant drop (90%) in traffic from Google to one of my well-established sites (6+ years) in the last week. Searches show that the top 3 wide keywords all dropped 4 spots. Searches for other keywords do not show ANY results in the first 10 to 25 pages of results, while previously one 1st or 2nd page at most. Since there are 200 factors for ranking, the question really is: What steps are necesary to figure out what caused such a drop? There has been no major changes during this period or the last month on the site and certainly not in the homepage which has dropped rank. Over all the years of running this site and plenty of others, I have never experienced this. There are no duplicate content on my site and I have rigorously used canonical links for the last few years to ensure it is not misinterpreted as such.

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  • Has programming ruined your perception of round numbers?

    - by Jon Purdy
    Most of the world works in base 10 nowadays, but as programmers working on binary systems, we constantly find ourselves working with powers of 2. While most people consider integer multiples of powers of 10 "nice and round" and somehow aesthetically superior, I found early on in my programming adventures that multiples of powers of 2 feel much more intuitively round to me: fewer factors, of course. I'm much more likely to lay out a Web site using, say, 8- or 16-pixel margins rather than 10 or 20, and when someone remarks that 128 is an insanely arbitrary number of ounces to be in a gallon, I have to smile a little inside at how, just perhaps, the U.S. system might be superior to metric in one small way. I'm just curious: has programming ruined (read: altered) your perception of the roundness of a number?

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  • Project Euler 3: (Iron)Python

    - by Ben Griswold
    In my attempt to learn (Iron)Python out in the open, here’s my solution for Project Euler Problem 3.  As always, any feedback is welcome. # Euler 3 # http://projecteuler.net/index.php?section=problems&id=3 # The prime factors of 13195 are 5, 7, 13 and 29. # What is the largest prime factor of the number # 600851475143? import time start = time.time() def largest_prime_factor(n): max = n divisor = 2 while (n >= divisor ** 2): if n % divisor == 0: max, n = n, n / divisor else: divisor += 1 return max print largest_prime_factor(600851475143) print "Elapsed Time:", (time.time() - start) * 1000, "millisecs" a=raw_input('Press return to continue')

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  • Mark Hurd on the Customer Revolution: Oracle's Top 10 Insights

    - by Richard Lefebvre
    Reprint of an article from Forbes Businesses that fail to focus on customer experience will hear a giant sucking sound from their vanishing profitability. Because in today’s dynamic global marketplace, consumers now hold the power in the buyer-seller equation, and sellers need to revamp their strategy for this new world order. The ability to relentlessly deliver connected, personalized and rewarding customer experiences is rapidly becoming one of the primary sources of competitive advantage in today’s dynamic global marketplace. And the inability or unwillingness to realize that the customer is a company’s most important asset will lead, inevitably, to decline and failure. Welcome to the lifecycle of customer experience, in which consumers explore, engage, shop, buy, ask, compare, complain, socialize, exchange, and more across multiple channels with the unconditional expectation that each of those interactions will be completed in an efficient and personalized manner however, wherever, and whenever the customer wants. While many niche companies are offering point solutions within that sprawling and complex spectrum of needs and requirements, businesses looking to deliver superb customer experiences are still left having to do multiple product evaluations, multiple contract negotiations, multiple test projects, multiple deployments, and–perhaps most annoying of all–multiple and never-ending integration projects to string together all those niche products from all those niche vendors. With its new suite of customer-experience solutions, Oracle believes it can help companies unravel these challenges and move at the speed of their customers, anticipating their needs and desires and creating enduring and profitable relationships. Those solutions span the full range of marketing, selling, commerce, service, listening/insights, and social and collaboration tools for employees. When Oracle launched its suite of Customer Experience solutions at a recent event in New York City, president Mark Hurd analyzed the customer experience revolution taking place and presented Oracle’s strategy for empowering companies to capitalize on this important market shift. From Hurd’s presentation and related materials, I’ve extracted a list of Hurd’s Top 10 Insights into the Customer Revolution. 1. Please Don’t Feed the Competitor’s Pipeline!After enduring a poor experience, 89% of consumers say they would immediately take their business to your competitor. (Except where noted, the source for these findings is the 2011 Customer Experience Impact (CEI) Report including a survey commissioned by RightNow (acquired by Oracle in March 2012) and conducted by Harris Interactive.) 2. The Addressable Market Is Massive. Only 1% of consumers say their expectations were always met by their actual experiences. 3. They’re Willing to Pay More! In return for a great experience, 86% of consumers say they’ll pay up to 25% more. 4. The Social Media Microphone Is Always Live. After suffering through a poor experience, more than 25% of consumers said they posted a negative comment on Twitter or Facebook or other social media sites. Conversely, of those consumers who got a response after complaining, 22% posted positive comments about the company. 5.  The New Deal Is Never Done: Embrace the Entire Customer Lifecycle. An appropriately active and engaged relationship, says Hurd, extends across every step of the entire processs: need, research, select, purchase, receive, use, maintain, and recommend. 6. The 360-Degree Commitment. Customers want to do business with companies that actively and openly demonstrate the desire to establish strong and seamless connections across employees, the company, and the customer, says research firm Temkin Group in its report called “The CX Competencies.” 7. Understand the Emotional Drivers Behind Brand Love. What makes consumers fall in love with a brand? Among the top factors are friendly employees and customer reps (73%), easy access to information and support (55%), and personalized experiences, such as when companies know precisely what products or services customers have purchased in the past and what issues those customers have raised (36%). 8.  The Importance of Immediate Action. You’ve got one week to respond–and then the opportunity’s lost. If your company needs more than a week to answer a prospect’s question or request, most of those prospects will terminate the relationship. 9.  Want More Revenue, Less Churn, and More Referrals? Then improve the overall customer experience: Forrester’s research says that approach put an extra $900 million in the pockets of wireless service providers, $800 million for hotels, and $400 million for airlines. 10. The Formula for CX Success.  Hurd says it includes three elegantly interlaced factors: Connected Engagement, to personalize the experience; Actionable Insight, to maximize the engagement; and Optimized Execution, to deliver on the promise of value. RECOMMENDED READING: The Top 10 Strategic CIO Issues For 2013 Wal-Mart, Amazon, eBay: Who’s the Speed King of Retail? Career Suicide and the CIO: 4 Deadly New Threats Memo to Marc Benioff: Social Is a Tool, Not an App

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  • Oracle Retail Consulting and the Implementation Process, with Maria Porretta

    - by user801960
    Maria Porretta, Engagement Director, discusses Oracle Retail Consulting and its involvement in the implementation process and how it supports customers to maximize their ROI in Oracle Retail solutions. Maria explains the wide range of factors customers need to consider when preparing to implement Oracle Retail, from the solutions being utilized to the current IT infrastructures and available resources of the end user. Oracle Retail Consulting ensures a smooth and efficient process by working with customers from design right through to final implementation, and continues to work with customers to ensure they get value from their software investments and further extend investment in Oracle Retail solutions. Further information is available on our website regarding Oracle Retail Consulting.

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  • Are keyboard layouts inherently flawed for programmers?

    - by Craige
    Lately I've been noticing my keyboard usage more and more and how it affects my productivity. It brought to mind a question/problem that I believe has not been truly solved in the programming community (partially based on individual preferences). Are all/most keyboard layouts inherently flawed for programmers? What changes to your keyboard layout do you feel would increase your productivity most? Edit Remember when answering that there are a number of different factors that could make a keyboard layout flawed. For instance, if you type as fast as you believe you need to, but hitting common keys is uncomfortable, said keyboard layout could be considered flawed.

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  • Register now for the FREE Tech Days Online Conference January 20th

    - by Eric Nelson
    The perfect solution to the “January blues” is a good solid few hours learning about great technology. The 'Build an app for that' Online Conference is exactly that, featuring demo-rich sessions on building applications for the browser, Windows 7, and Windows Phone 7. There are three tracks letting you choose which sessions are most relevant to you - whether you're just considering client development with Silverlight, or you've already got stuck in to an advanced project. We'll also explore new form factors such as Phone and Slate, and how to develop touch-based applications. Finally we'll cover the important subject of how to create beautifully designed user interfaces. Register now Agenda:

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  • Quality Backlinks - A Key to Search Engine Optimization

    Backlinks are the links which are going to your blogs, sites or articles. Backlinks are the most important and single very significant factors to give the page rank to your site or blogs.They are great technique and way to find a proper and a decent place in the goggle or any of the major search engines. There are many other aspects of SEO but quality back links are the most appropriate way to find a great way in terms of search engine optimization. Now it is the time to take a look at the components which are very important about backlinks.

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  • How do I know when should I package my classes in Ruby?

    - by Omega
    In Ruby, I'm creating a small game development framework. Just some personal project - a very small group of friends helping. Now I am in need of handling geometric concepts. Rectangles, Circles, Polygons, Vectors, Lines, etc. So I made a class for each of these. I'm stuck deciding whether I should package such classes in a module, such as Geometry. So I'd access them like Geometry::Rectangle, or just Rectangle if I include the module. Now then, my question isn't about this specific scenario. I'd like to know, when is it suitable to package similar classes into one module in Ruby? What factors should I consider? Amount of classes? Usage frequency? Complexity?

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  • Taking a Flying Leap

    - by Lance Shaw
    Yesterday, I went skydiving with three of my children.  It was thrilling, scary, invigorating and exciting. While there is obvious risk involved, the reward and feeling of success was well worth it. You might already be wondering what skydiving would have to with WebCenter, so let me explain. Implementing a skydiving program and becoming an instructor does not happen overnight.  It does not happen with the purchase of the needed technology. Not one of us would go out, buy a parachute, the harnesses, helmet and all the gear and be able to convince anyone that we are now ready to be a skydiving instructor. The fact is that obtaining the technology is merely a small piece of the overall process and so is the case with managing content in your company. You don't just buy the right software (Oracle WebCenter Content) and go to your boss and declare information management success. There is planning, research and effort that goes into deploying software of any kind and especially when it is as mission-critical to the success of your business as Enterprise Content Management. To become a certified skydiving instructor takes at least 3 years of commitment and often longer. In the United States, candidates must complete over 500 solo jumps of their own over a minimum of 36 months and then must complete additional rigorous training under observation.  When you consider the amount of time and effort involved, it's not unlike getting a college degree and anyone that has trusted their lives to one of these instructors will no doubt appreciate their dedication to the curriculum.  Implementing an ECM system won't take that long, but it certainly requires commitment, analysis and consideration. But guess what?  Humans are involved and that means that mistakes can happen and that rules change.  This struck me while reading an excellent post on darkreading.com by Glenn S. Phillips entitled "Mission Impossible: 4 Reasons Compliance is Impossible".  His over-arching point was that with information management and security, environments change and people are involved meaning the work is never done.  He stated that you can never claim your compliance efforts are complete because of the following reasons. People are involved.  And lets face it, some are more trustworthy than others. Change is Constant. There is always some new technology coming along that is disruptive. Consumer grade cloud file sharing and sync tools come to mind here. Compliance is interpreted, not defined.  Laws and the judges that read them are always on the move. Technology is a tool, not a complete solution. There is no magic pill. The skydiving analogy holds true here as well.  Ultimately, a single person packs your parachute.  For obvious reasons, you prefer that this person be trustworthy but there are no absolute guarantees of a 100% error-free scenario.  Weather and wind conditions are never a constant and the best-laid plans for a great day of skydiving are easily disrupted by forces outside of your control.  Rules and regulations vary by location and may be updated at any time and as I mentioned early on, even the best technology on its own will only get you started. The good news is that, like skydiving, with the right technology, the right planning, the right team and a proper understanding of the rules and regulations that govern your industry, your ECM deployment can be a great success.  Failure to plan for any of the 4 factors that Glenn outlined in his article will certainly put your deployment and maybe even your company at risk, so consider them carefully. As a final aside, for those of you who consider skydiving an incredibly dangerous and risky pastime, consider this comparative statistic.  In 2012, the U.S. Parachute Association recorded 19 fatal skydiving accidents in the U.S. out of roughly 3.1 million jumps.  That’s 0.006 fatalities per 1,000 jumps. By comparison, the U.S. National Highway Traffic Safety Administration reports that there were 34,080 deaths due to car accidents in 2012.  Based on the percentages, one could argue that it is safer to jump out of a plane than to drive to the airport where the skydiving will take place. While the way you manage, secure, classify, control, retain and dispose of company files may not carry as much risk as driving or skydiving, it certainly carries risk for the organization when not planned and deployed appropriately.  Consider all the factors involved in your organization as you make your content management plans.  For additional areas of consideration, be sure to download our free whitepaper on the topic entitled "The Top 10 Criteria for Choosing an ECM System" which is available for download here.

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  • Using disqus for a website (question on SERP and backlink)

    - by Homunculus Reticulli
    I am building a website and am trying to decide between writing my own commenting system and using disquss. One of the main deciding factors is that (obviously), I want comments left on my page to be show on SERPS. However, I remeber reading somewhere that disqus loads comments into a page using AJAX - and therefore the comments are "invisible" as far as Googlebot and other SE crawlers are concerned. Could someone confirm or refute this? The other question I have is about whether (as a commenter), When I place a comment on another website using disqus (including any links I may add to my comment), do the lionks in my comment count as a backlink (in other words are they "dofollow" or "nofollow" links)?

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  • How to make a great functional specification

    - by sfrj
    I am going to start a little side project very soon, but this time i want to do not just the little UML domain model and case diagrams i often do before programming, i thought about making a full functional specification. Is there anybody that has experience writing functional specifications that could recommend me what i need to add to it? How would be the best way to start preparing it? Here i will write down the topics that i think are more relevant: Purpose Functional Overview Context Diagram Critical Project Success Factors Scope (In & Out) Assumptions Actors (Data Sources, System Actors) Use Case Diagram Process Flow Diagram Activity Diagram Security Requirements Performance Requirements Special Requirements Business Rules Domain Model (Data model) Flow Scenarios (Success, alternate…) Time Schedule (Task Management) Goals System Requirements Expected Expenses What do you think about those topics? Shall i add something else? or maybe remove something?

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  • Canonical links for huge websites

    - by Florin
    Let's say I have 5 products that are identical but the product code, the product color specifications and the product image. The title, meta and description are identical (by the way the color is in a select form). I made 4 products link canonical to the 1 that is the master based on many factors. If the master becomes inactive or without a stock one product from the other 4 will become the new master and the rest will become canonical to it. The question is if that by becomeing master from canonical will the site suffer a penalty from Google or it will work just fine? What will Google think about this strategy?

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  • Cloud Odyssey: A Hero's Quest Wins Two Telly Awards!

    - by Sandra Cheevers
    Cloud Odyssey: A Hero's Quest is a sci-fi movie experience that shows you the key success factors for guiding your own journey to the cloud.   The movie shows the journey to a mysterious cloud planet, as a metaphor to YOUR journey to the cloud. And now, Cloud Odyssey: A Hero's Quest! receives 2 Telly awards in the categories 1) Motivational and 2) Use of Animation. This is truly an honor to be recognized in the company of so many outstanding entries from a wide range of major players, including Disney, Coca-Cola, NBC, Discovery...Kudos to the Cloud Odyssey team!

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  • PHP and performance

    - by Naif
    I always hear that PHP is for medium and small websites whereas .NET and Java for enterprise applications. My question is about PHP. Why is PHP not a good option for enterprise web applications? Is it because if the web application becomes bigger then PHP will be slower as it is an interpreted language? I know that corporate world will choose .NET or J2EE because of the integration with their products and because of back end services, etc. However, if we just have PHP for building sites and web applications then how can we use it to perform well with big sites? In short, Is there a relationship between the performance of PHP and the size of the website? What are the factors that make PHP not appropriate option for big sites?

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  • Performance triage

    - by Dave
    Folks often ask me how to approach a suspected performance issue. My personal strategy is informed by the fact that I work on concurrency issues. (When you have a hammer everything looks like a nail, but I'll try to keep this general). A good starting point is to ask yourself if the observed performance matches your expectations. Expectations might be derived from known system performance limits, prototypes, and other software or environments that are comparable to your particular system-under-test. Some simple comparisons and microbenchmarks can be useful at this stage. It's also useful to write some very simple programs to validate some of the reported or expected system limits. Can that disk controller really tolerate and sustain 500 reads per second? To reduce the number of confounding factors it's better to try to answer that question with a very simple targeted program. And finally, nothing beats having familiarity with the technologies that underlying your particular layer. On the topic of confounding factors, as our technology stacks become deeper and less transparent, we often find our own technology working against us in some unexpected way to choke performance rather than simply running into some fundamental system limit. A good example is the warm-up time needed by just-in-time compilers in Java Virtual Machines. I won't delve too far into that particular hole except to say that it's rare to find good benchmarks and methodology for java code. Another example is power management on x86. Power management is great, but it can take a while for the CPUs to throttle up from low(er) frequencies to full throttle. And while I love "turbo" mode, it makes benchmarking applications with multiple threads a chore as you have to remember to turn it off and then back on otherwise short single-threaded runs may look abnormally fast compared to runs with higher thread counts. In general for performance characterization I disable turbo mode and fix the power governor at "performance" state. Another source of complexity is the scheduler, which I've discussed in prior blog entries. Lets say I have a running application and I want to better understand its behavior and performance. We'll presume it's warmed up, is under load, and is an execution mode representative of what we think the norm would be. It should be in steady-state, if a steady-state mode even exists. On Solaris the very first thing I'll do is take a set of "pstack" samples. Pstack briefly stops the process and walks each of the stacks, reporting symbolic information (if available) for each frame. For Java, pstack has been augmented to understand java frames, and even report inlining. A few pstack samples can provide powerful insight into what's actually going on inside the program. You'll be able to see calling patterns, which threads are blocked on what system calls or synchronization constructs, memory allocation, etc. If your code is CPU-bound then you'll get a good sense where the cycles are being spent. (I should caution that normal C/C++ inlining can diffuse an otherwise "hot" method into other methods. This is a rare instance where pstack sampling might not immediately point to the key problem). At this point you'll need to reconcile what you're seeing with pstack and your mental model of what you think the program should be doing. They're often rather different. And generally if there's a key performance issue, you'll spot it with a moderate number of samples. I'll also use OS-level observability tools to lock for the existence of bottlenecks where threads contend for locks; other situations where threads are blocked; and the distribution of threads over the system. On Solaris some good tools are mpstat and too a lesser degree, vmstat. Try running "mpstat -a 5" in one window while the application program runs concurrently. One key measure is the voluntary context switch rate "vctx" or "csw" which reflects threads descheduling themselves. It's also good to look at the user; system; and idle CPU percentages. This can give a broad but useful understanding if your threads are mostly parked or mostly running. For instance if your program makes heavy use of malloc/free, then it might be the case you're contending on the central malloc lock in the default allocator. In that case you'd see malloc calling lock in the stack traces, observe a high csw/vctx rate as threads block for the malloc lock, and your "usr" time would be less than expected. Solaris dtrace is a wonderful and invaluable performance tool as well, but in a sense you have to frame and articulate a meaningful and specific question to get a useful answer, so I tend not to use it for first-order screening of problems. It's also most effective for OS and software-level performance issues as opposed to HW-level issues. For that reason I recommend mpstat & pstack as my the 1st step in performance triage. If some other OS-level issue is evident then it's good to switch to dtrace to drill more deeply into the problem. Only after I've ruled out OS-level issues do I switch to using hardware performance counters to look for architectural impediments.

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  • High Availability for IaaS, PaaS and SaaS in the Cloud

    - by BuckWoody
    Outages, natural disasters and unforeseen events have proved that even in a distributed architecture, you need to plan for High Availability (HA). In this entry I'll explain a few considerations for HA within Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS). In a separate post I'll talk more about Disaster Recovery (DR), since each paradigm has a different way to handle that. Planning for HA in IaaS IaaS involves Virtual Machines - so in effect, an HA strategy here takes on many of the same characteristics as it would on-premises. The primary difference is that the vendor controls the hardware, so you need to verify what they do for things like local redundancy and so on from the hardware perspective. As far as what you can control and plan for, the primary factors fall into three areas: multiple instances, geographical dispersion and task-switching. In almost every cloud vendor I've studied, to ensure your application will be protected by any level of HA, you need to have at least two of the Instances (VM's) running. This makes sense, but you might assume that the vendor just takes care of that for you - they don't. If a single VM goes down (for whatever reason) then the access to it is lost. Depending on multiple factors, you might be able to recover the data, but you should assume that you can't. You should keep a sync to another location (perhaps the vendor's storage system in another geographic datacenter or to a local location) to ensure you can continue to serve your clients. You'll also need to host the same VM's in another geographical location. Everything from a vendor outage to a network path problem could prevent your users from reaching the system, so you need to have multiple locations to handle this. This means that you'll have to figure out how to manage state between the geo's. If the system goes down in the middle of a transaction, you need to figure out what part of the process the system was in, and then re-create or transfer that state to the second set of systems. If you didn't write the software yourself, this is non-trivial. You'll also need a manual or automatic process to detect the failure and re-route the traffic to your secondary location. You could flip a DNS entry (if your application can tolerate that) or invoke another process to alias the first system to the second, such as load-balancing and so on. There are many options, but all of them involve coding the state into the application layer. If you've simply moved a state-ful application to VM's, you may not be able to easily implement an HA solution. Planning for HA in PaaS Implementing HA in PaaS is a bit simpler, since it's built on the concept of stateless applications deployment. Once again, you need at least two copies of each element in the solution (web roles, worker roles, etc.) to remain available in a single datacenter. Also, you need to deploy the application again in a separate geo, but the advantage here is that you could work out a "shared storage" model such that state is auto-balanced across the world. In fact, you don't have to maintain a "DR" site, the alternate location can be live and serving clients, and only take on extra load if the other site is not available. In Windows Azure, you can use the Traffic Manager service top route the requests as a type of auto balancer. Even with these benefits, I recommend a second backup of storage in another geographic location. Storage is inexpensive; and that second copy can be used for not only HA but DR. Planning for HA in SaaS In Software-as-a-Service (such as Office 365, or Hadoop in Windows Azure) You have far less control over the HA solution, although you still maintain the responsibility to ensure you have it. Since each SaaS is different, check with the vendor on the solution for HA - and make sure you understand what they do and what you are responsible for. They may have no HA for that solution, or pin it to a particular geo, or perhaps they have a massive HA built in with automatic load balancing (which is often the case).   All of these options (with the exception of SaaS) involve higher costs for the design. Do not sacrifice reliability for cost - that will always cost you more in the end. Build in the redundancy and HA at the very outset of the project - if you try to tack it on later in the process the business will push back and potentially not implement HA. References: http://www.bing.com/search?q=windows+azure+High+Availability  (each type of implementation is different, so I'm routing you to a search on the topic - look for the "Patterns and Practices" results for the area in Azure you're interested in)

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