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  • Should software engineers take the upcoming PE exam for software engineering?

    - by jschmier
    I realize that this question is quite similar to this one, but news of a PE exam being developed specifically for software engineering by the NCEES and IEEE has piqued my interest. Should software engineering professionals take the (upcoming) PE exam for software engineering in addition to their degree (or relevant work experience)? Note: I realize the exam being developed is still sometime away, but I'm curious about the thoughts of the professionals active on Stack Overflow.

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  • What makes good software good?

    - by Jonta
    People probably have a lot of different answers here, like good...: scalability, speed, usability, stability, consistency, completeness, absence of bugs, accessibility, documentation, code-quality and so on. There are a lot of philosophies on development of software. Like the UNIX-philosophy. Often vague and not easy to understand. I am looking for statements such as the one cited below. Which you can ask about the software when it's in the design-stage, is ready to be coded, and has been coded and is ready for launch. The software I am talking about, is of course the software made for the end-user. Ken Rockwell wrote: "I expect that it will let me get more accomplished in less time." (Here one could ask "will this let me get more accomplished in less time?")

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  • What's the case when using software licensed under GPL or LGPL

    - by Johnas
    With everything legal and in line with the ethical questions in software development, is it allowed to use an open source product in my software that I charge a fee for when selling? Scenario: I've developed an PHP Content Management System (CMS) and use some Linux executables licensed under GPL or LGPL in my CMS to accomplish various tasks like image editing. I'm selling the CMS and also including the executables when I deliver the product. I do not edit the source code of the GPL software, just using it.

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  • What are the differences between enterprise software/architecture patterns and open source software?

    - by Jeffrey
    I am mainly a business app developer and I hear terms like CQRS, ServiceBus, SOA, DDD, BDD, AOP a lot. My question is that do these patterns/practices exist only in the "enterprise" world? In contract to the enterprise world is the open source community. Highly trafficked sites like Digg, LiveJournal whenever there is an article mentioning about how they built/scaled their sites all I am hearing is what open source software (Memcached, NoSQL) they used in order to scale/simplify the way they tackle software problems and they rarely mention those above terms. Is it because they are not as sophisticated as those of enterprise level software (I doubt it)? Or are people just making up those terms/practices/patterns in order to keep them jobs? Or am I confusing myself with differences between software development and internet website scaling?

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  • Pros and Cons of Proprietary Software

    - by Jon Purdy
    Proprietary software is about as good as open-source software. There are so many problems with proprietary technologies, however, that I'm beginning to think it's best to avoid them: The software will only be maintained as long as the company exists (and profits). The level of security of the application is as unknowable as the source code. Alterations and derivative works, however necessary and beneficial, are disallowed. I simply don't see any point in even learning to use such systems as those created by Microsoft and Apple. Of course I don't pretend that ignorance is the superior option: one has to have a certain working knowledge simply because of the ubiquity of these things. I just don't see any reason why, as an independent developer, I should ever consider it a remotely good idea to actually use them. So that's the question, or discussion topic, or what have you: In what ways do developers benefit at all from using closed-source development software?

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  • Software Engineering Component Repository Tool

    - by user320480
    Hello, I'm working as a software engineer for a company. We are going to apply some software engineering standards in our development process. We need a tool which provides a repository for our peripheral products (functions, classes, libraries, ...) which is created during software development process for later use. The tool should provide some functionalities (e.g Name of the component, it's functionality, withing which projects it is used?, author, publication date, list of known bugs, user rating, comment, ...) and it's better to have a web-based interface. Does anybody know such a software?

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  • Surface development: it&rsquo;s just like software development

    - by Dennis Vroegop
    Surface is magic. Everyone using it seems to think that way. And I have to be honest, after working for almost 2 years with the platform I still get that special feeling the moment I turn on the unit to do some more work. The whole user experience, the rich environment of the SDK, the touch, even the look and feel of the Surface environment is so much different from the stuff I’ve been working on all my career that I am still bewildered by it. But… and this is a big but.. in the end we’re still talking about a computer and that needs software to become useful. Deep down the magic of the Surface unit there is a PC somewhere, running Windows Vista and the .net framework 3.5. When you write that magic software that makes the platform come alive you’re still working with .net, WPF/XNA, C#, VB.Net and all those other tools and technologies you know so well. Sure, the whole user experience is different from what you’ve known. And the way of thinking about users, their interaction and the positioning of screen elements requires a whole new paradigm. And that takes time. It took me about half a year before I had the feeling I got it nailed down. But when that moment came (about 18 months ago…) I realized that everything I had learned so far on software development still is true when it comes to Surface. The last 6 months I have been working with some people with a different background to start a new company. The idea was that the new company would be focussing on Surface and Surface only. These people come from a marketing background and had some good ideas for some applications. And I have to admit: their ideas were good. Very good. Where it all fell down of course is that these ideas need to be implemented in a piece of software. And creating great software takes skilled developers and a lot of time and money. That’s where things went wrong: the marketing guys didn’t realize and didn’t want to realize that software development is a job that takes skill. You can’t just hire a bunch of developers and expect them to deliver the best sort of software, especially not when it comes to Surface. I tried to explain that yes, their User Interface in Photoshop looked great, but no: I couldn’t develop an application like that in a weeks time. Even worse: the while backend of the software (WCF for communications, SQL Server for the database, etc) would take a lot more time than the frontend. They didn’t understand. It took them a couple of days to drawn the UI in Photoshop so in Blend I should be able to build the software in about the same amount of time. Well, you and I know that it doesn’t work that way. Software is hard to write, and even harder to write well, and it takes skill and dedication. It’s not something you can do as fast as you can draw a mock up for a Surface application in Photohop. The same holds true for web applications of course. A lot of designers there fail to appreciate the hard work that goes into writing the plumbing for a good web app that can handle thousands of users. Although the UI is very important, it’s not all there is to it. And in Surface development this is the same. The UI should create the feeling of magic, but the software behind it is what makes it come alive. And that takes time. A lot of time. So brush of you skills and don’t throw them away if you start developing for Surface. Because projects (and colaborations) can fail there as hard as they can in any other area of software development. On a side note: we decided to stop the colaboration (something the other parties involved didn’t appreciate and were very angry about) and decided to hire a designer for the Surface projects. The focus is back where it belongs: on the software development we know so well and have been doing very well for 13 years. UI is just a part of the whole project and not the end product. So my company Detrio is still going strong when it comes to develivering Surface solutions but once again from a technological background, not a marketing background.

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  • The Benefits of Smart Grid Business Software

    - by Sylvie MacKenzie, PMP
    Smart Grid Background What Are Smart Grids?Smart Grids use computer hardware and software, sensors, controls, and telecommunications equipment and services to: Link customers to information that helps them manage consumption and use electricity wisely. Enable customers to respond to utility notices in ways that help minimize the duration of overloads, bottlenecks, and outages. Provide utilities with information that helps them improve performance and control costs. What Is Driving Smart Grid Development? Environmental ImpactSmart Grid development is picking up speed because of the widespread interest in reducing the negative impact that energy use has on the environment. Smart Grids use technology to drive efficiencies in transmission, distribution, and consumption. As a result, utilities can serve customers’ power needs with fewer generating plants, fewer transmission and distribution assets,and lower overall generation. With the possible exception of wind farm sprawl, landscape preservation is one obvious benefit. And because most generation today results in greenhouse gas emissions, Smart Grids reduce air pollution and the potential for global climate change.Smart Grids also more easily accommodate the technical difficulties of integrating intermittent renewable resources like wind and solar into the grid, providing further greenhouse gas reductions. CostsThe ability to defer the cost of plant and grid expansion is a major benefit to both utilities and customers. Utilities do not need to use as many internal resources for traditional infrastructure project planning and management. Large T&D infrastructure expansion costs are not passed on to customers.Smart Grids will not eliminate capital expansion, of course. Transmission corridors to connect renewable generation with customers will require major near-term expenditures. Additionally, in the future, electricity to satisfy the needs of population growth and additional applications will exceed the capacity reductions available through the Smart Grid. At that point, expansion will resume—but with greater overall T&D efficiency based on demand response, load control, and many other Smart Grid technologies and business processes. Energy efficiency is a second area of Smart Grid cost saving of particular relevance to customers. The timely and detailed information Smart Grids provide encourages customers to limit waste, adopt energy-efficient building codes and standards, and invest in energy efficient appliances. Efficiency may or may not lower customer bills because customer efficiency savings may be offset by higher costs in generation fuels or carbon taxes. It is clear, however, that bills will be lower with efficiency than without it. Utility Operations Smart Grids can serve as the central focus of utility initiatives to improve business processes. Many utilities have long “wish lists” of projects and applications they would like to fund in order to improve customer service or ease staff’s burden of repetitious work, but they have difficulty cost-justifying the changes, especially in the short term. Adding Smart Grid benefits to the cost/benefit analysis frequently tips the scales in favor of the change and can also significantly reduce payback periods.Mobile workforce applications and asset management applications work together to deploy assets and then to maintain, repair, and replace them. Many additional benefits result—for instance, increased productivity and fuel savings from better routing. Similarly, customer portals that provide customers with near-real-time information can also encourage online payments, thus lowering billing costs. Utilities can and should include these cost and service improvements in the list of Smart Grid benefits. What Is Smart Grid Business Software? Smart Grid business software gathers data from a Smart Grid and uses it improve a utility’s business processes. Smart Grid business software also helps utilities provide relevant information to customers who can then use it to reduce their own consumption and improve their environmental profiles. Smart Grid Business Software Minimizes the Impact of Peak Demand Utilities must size their assets to accommodate their highest peak demand. The higher the peak rises above base demand: The more assets a utility must build that are used only for brief periods—an inefficient use of capital. The higher the utility’s risk profile rises given the uncertainties surrounding the time needed for permitting, building, and recouping costs. The higher the costs for utilities to purchase supply, because generators can charge more for contracts and spot supply during high-demand periods. Smart Grids enable a variety of programs that reduce peak demand, including: Time-of-use pricing and critical peak pricing—programs that charge customers more when they consume electricity during peak periods. Pilot projects indicate that these programs are successful in flattening peaks, thus ensuring better use of existing T&D and generation assets. Direct load control, which lets utilities reduce or eliminate electricity flow to customer equipment (such as air conditioners). Contracts govern the terms and conditions of these turn-offs. Indirect load control, which signals customers to reduce the use of on-premises equipment for contractually agreed-on time periods. Smart Grid business software enables utilities to impose penalties on customers who do not comply with their contracts. Smart Grids also help utilities manage peaks with existing assets by enabling: Real-time asset monitoring and control. In this application, advanced sensors safely enable dynamic capacity load limits, ensuring that all grid assets can be used to their maximum capacity during peak demand periods. Real-time asset monitoring and control applications also detect the location of excessive losses and pinpoint need for mitigation and asset replacements. As a result, utilities reduce outage risk and guard against excess capacity or “over-build”. Better peak demand analysis. As a result: Distribution planners can better size equipment (e.g. transformers) to avoid over-building. Operations engineers can identify and resolve bottlenecks and other inefficiencies that may cause or exacerbate peaks. As above, the result is a reduction in the tendency to over-build. Supply managers can more closely match procurement with delivery. As a result, they can fine-tune supply portfolios, reducing the tendency to over-contract for peak supply and reducing the need to resort to spot market purchases during high peaks. Smart Grids can help lower the cost of remaining peaks by: Standardizing interconnections for new distributed resources (such as electricity storage devices). Placing the interconnections where needed to support anticipated grid congestion. Smart Grid Business Software Lowers the Cost of Field Services By processing Smart Grid data through their business software, utilities can reduce such field costs as: Vegetation management. Smart Grids can pinpoint momentary interruptions and tree-caused outages. Spatial mash-up tools leverage GIS models of tree growth for targeted vegetation management. This reduces the cost of unnecessary tree trimming. Service vehicle fuel. Many utility service calls are “false alarms.” Checking meter status before dispatching crews prevents many unnecessary “truck rolls.” Similarly, crews use far less fuel when Smart Grid sensors can pinpoint a problem and mobile workforce applications can then route them directly to it. Smart Grid Business Software Ensures Regulatory Compliance Smart Grids can ensure compliance with private contracts and with regional, national, or international requirements by: Monitoring fulfillment of contract terms. Utilities can use one-hour interval meters to ensure that interruptible (“non-core”) customers actually reduce or eliminate deliveries as required. They can use the information to levy fines against contract violators. Monitoring regulations imposed on customers, such as maximum use during specific time periods. Using accurate time-stamped event history derived from intelligent devices distributed throughout the smart grid to monitor and report reliability statistics and risk compliance. Automating business processes and activities that ensure compliance with security and reliability measures (e.g. NERC-CIP 2-9). Grid Business Software Strengthens Utilities’ Connection to Customers While Reducing Customer Service Costs During outages, Smart Grid business software can: Identify outages more quickly. Software uses sensors to pinpoint outages and nested outage locations. They also permit utilities to ensure outage resolution at every meter location. Size outages more accurately, permitting utilities to dispatch crews that have the skills needed, in appropriate numbers. Provide updates on outage location and expected duration. This information helps call centers inform customers about the timing of service restoration. Smart Grids also facilitates display of outage maps for customer and public-service use. Smart Grids can significantly reduce the cost to: Connect and disconnect customers. Meters capable of remote disconnect can virtually eliminate the costs of field crews and vehicles previously required to change service from the old to the new residents of a metered property or disconnect customers for nonpayment. Resolve reports of voltage fluctuation. Smart Grids gather and report voltage and power quality data from meters and grid sensors, enabling utilities to pinpoint reported problems or resolve them before customers complain. Detect and resolve non-technical losses (e.g. theft). Smart Grids can identify illegal attempts to reconnect meters or to use electricity in supposedly vacant premises. They can also detect theft by comparing flows through delivery assets with billed consumption. Smart Grids also facilitate outreach to customers. By monitoring and analyzing consumption over time, utilities can: Identify customers with unusually high usage and contact them before they receive a bill. They can also suggest conservation techniques that might help to limit consumption. This can head off “high bill” complaints to the contact center. Note that such “high usage” or “additional charges apply because you are out of range” notices—frequently via text messaging—are already common among mobile phone providers. Help customers identify appropriate bill payment alternatives (budget billing, prepayment, etc.). Help customers find and reduce causes of over-consumption. There’s no waiting for bills in the mail before they even understand there is a problem. Utilities benefit not just through improved customer relations but also through limiting the size of bills from customers who might struggle to pay them. Where permitted, Smart Grids can open the doors to such new utility service offerings as: Monitoring properties. Landlords reduce costs of vacant properties when utilities notify them of unexpected energy or water consumption. Utilities can perform similar services for owners of vacation properties or the adult children of aging parents. Monitoring equipment. Power-use patterns can reveal a need for equipment maintenance. Smart Grids permit utilities to alert owners or managers to a need for maintenance or replacement. Facilitating home and small-business networks. Smart Grids can provide a gateway to equipment networks that automate control or let owners access equipment remotely. They also facilitate net metering, offering some utilities a path toward involvement in small-scale solar or wind generation. Prepayment plans that do not need special meters. Smart Grid Business Software Helps Customers Control Energy Costs There is no end to the ways Smart Grids help both small and large customers control energy costs. For instance: Multi-premises customers appreciate having all meters read on the same day so that they can more easily compare consumption at various sites. Customers in competitive regions can match their consumption profile (detailed via Smart Grid data) with specific offerings from competitive suppliers. Customers seeing inexplicable consumption patterns and power quality problems may investigate further. The result can be discovery of electrical problems that can be resolved through rewiring or maintenance—before more serious fires or accidents happen. Smart Grid Business Software Facilitates Use of Renewables Generation from wind and solar resources is a popular alternative to fossil fuel generation, which emits greenhouse gases. Wind and solar generation may also increase energy security in regions that currently import fossil fuel for use in generation. Utilities face many technical issues as they attempt to integrate intermittent resource generation into traditional grids, which traditionally handle only fully dispatchable generation. Smart Grid business software helps solves many of these issues by: Detecting sudden drops in production from renewables-generated electricity (wind and solar) and automatically triggering electricity storage and smart appliance response to compensate as needed. Supporting industry-standard distributed generation interconnection processes to reduce interconnection costs and avoid adding renewable supplies to locations already subject to grid congestion. Facilitating modeling and monitoring of locally generated supply from renewables and thus helping to maximize their use. Increasing the efficiency of “net metering” (through which utilities can use electricity generated by customers) by: Providing data for analysis. Integrating the production and consumption aspects of customer accounts. During non-peak periods, such techniques enable utilities to increase the percent of renewable generation in their supply mix. During peak periods, Smart Grid business software controls circuit reconfiguration to maximize available capacity. Conclusion Utility missions are changing. Yesterday, they focused on delivery of reasonably priced energy and water. Tomorrow, their missions will expand to encompass sustainable use and environmental improvement.Smart Grids are key to helping utilities achieve this expanded mission. But they come at a relatively high price. Utilities will need to invest heavily in new hardware, software, business process development, and staff training. Customer investments in home area networks and smart appliances will be large. Learning to change the energy and water consumption habits of a lifetime could ultimately prove even more formidable tasks.Smart Grid business software can ease the cost and difficulties inherent in a needed transition to a more flexible, reliable, responsive electricity grid. Justifying its implementation, however, requires a full understanding of the benefits it brings—benefits that can ultimately help customers, utilities, communities, and the world address global issues like energy security and climate change while minimizing costs and maximizing customer convenience. This white paper is available for download here. For further information about Oracle's Primavera Solutions for Utilities, please read our Utilities e-book.

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  • Linux software raid fails to include one device for one RAID1 array

    - by user1389890
    One of my four Linux software raid arrays drops one of its two devices when I reboot my system. The other three arrays work fine. I am running RAID1 on kernel version 2.6.32-5-amd64. Every time I reboot, /dev/md2 comes up with only one device. I can manually add the device by saying $ sudo mdadm /dev/md2 --add /dev/sdc1. This works fine, and mdadm confirms that the device has been re-added as follows: mdadm: re-added /dev/sdc1 After adding the device and and allowing the array time to resynch, this is what the output of $ cat /proc/mdstat looks like: Personalities : [raid1] md3 : active raid1 sda4[0] sdb4[1] 244186840 blocks super 1.2 [2/2] [UU] md2 : active raid1 sdc1[0] sdd1[1] 732574464 blocks [2/2] [UU] md1 : active raid1 sda3[0] sdb3[1] 722804416 blocks [2/2] [UU] md0 : active raid1 sda1[0] sdb1[1] 6835520 blocks [2/2] [UU] unused devices: <none> Then after I reboot, this is what the output of $ cat /proc/mdstat looks like: Personalities : [raid1] md3 : active raid1 sda4[0] sdb4[1] 244186840 blocks super 1.2 [2/2] [UU] md2 : active raid1 sdd1[1] 732574464 blocks [2/1] [_U] md1 : active raid1 sda3[0] sdb3[1] 722804416 blocks [2/2] [UU] md0 : active raid1 sda1[0] sdb1[1] 6835520 blocks [2/2] [UU] unused devices: <none> During reboot, here is the output of $ sudo cat /var/log/syslog | grep mdadm : Jun 22 19:00:08 rook mdadm[1709]: RebuildFinished event detected on md device /dev/md2 Jun 22 19:00:08 rook mdadm[1709]: SpareActive event detected on md device /dev/md2, component device /dev/sdc1 Jun 22 19:00:20 rook kernel: [ 7819.446412] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.446415] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.446782] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.446785] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.515844] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.515847] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.606829] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.606832] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:48 rook kernel: [ 8027.855616] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:48 rook kernel: [ 8027.855620] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:48 rook kernel: [ 8027.855950] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:48 rook kernel: [ 8027.855952] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:49 rook kernel: [ 8027.962169] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:49 rook kernel: [ 8027.962171] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:49 rook kernel: [ 8028.054365] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:49 rook kernel: [ 8028.054368] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.588662] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.588664] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.601990] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.601991] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.602693] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.602695] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.605981] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.605983] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.606138] mdadm: sending ioctl 800c0910 to a partition! Jun 22 19:10:23 rook kernel: [ 9.606139] mdadm: sending ioctl 800c0910 to a partition! Jun 22 19:10:48 rook mdadm[1737]: DegradedArray event detected on md device /dev/md2 Here is the mdadm.conf file: ARRAY /dev/md0 metadata=0.90 UUID=92121d42:37f46b82:926983e9:7d8aad9b ARRAY /dev/md1 metadata=0.90 UUID=9c1bafc3:1762d51d:c1ae3c29:66348110 ARRAY /dev/md2 metadata=0.90 UUID=98cea6ca:25b5f305:49e8ec88:e84bc7f0 ARRAY /dev/md3 metadata=1.2 name=rook:3 UUID=ca3fce37:95d49a09:badd0ddc:b63a4792 I also ran $ sudo smartctl -t long /dev/sdc and no hardware issues were detected. As long as I do not reboot, /dev/md2 seems to work fine. Does anyone have any suggestions? Here is the output of $ sudo mdadm -E /dev/sdc1 after re-adding the device and letting it resync: /dev/sdc1: Magic : a92b4efc Version : 0.90.00 UUID : 98cea6ca:25b5f305:49e8ec88:e84bc7f0 (local to host rook) Creation Time : Sun Jul 13 08:05:55 2008 Raid Level : raid1 Used Dev Size : 732574464 (698.64 GiB 750.16 GB) Array Size : 732574464 (698.64 GiB 750.16 GB) Raid Devices : 2 Total Devices : 2 Preferred Minor : 2 Update Time : Mon Jun 24 07:42:49 2013 State : clean Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Checksum : 5fd6cc13 - correct Events : 180998 Number Major Minor RaidDevice State this 0 8 33 0 active sync /dev/sdc1 0 0 8 33 0 active sync /dev/sdc1 1 1 8 49 1 active sync /dev/sdd1 Here is the output of $ sudo mdadm -D /dev/md2 after re-adding the device and letting it resync: /dev/md2: Version : 0.90 Creation Time : Sun Jul 13 08:05:55 2008 Raid Level : raid1 Array Size : 732574464 (698.64 GiB 750.16 GB) Used Dev Size : 732574464 (698.64 GiB 750.16 GB) Raid Devices : 2 Total Devices : 2 Preferred Minor : 2 Persistence : Superblock is persistent Update Time : Mon Jun 24 07:42:49 2013 State : clean Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 UUID : 98cea6ca:25b5f305:49e8ec88:e84bc7f0 (local to host rook) Events : 0.180998 Number Major Minor RaidDevice State 0 8 33 0 active sync /dev/sdc1 1 8 49 1 active sync /dev/sdd1

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  • Upon reboot, Linux software raid fails to include one device of a RAID1 array

    - by user1389890
    One of my four Linux software raid arrays drops one of its two devices when I reboot my system. The other three arrays work fine. I am running RAID1 on kernel version 2.6.32-5-amd64 (Debian Squeeze). Every time I reboot, /dev/md2 comes up with only one device. I can manually add the device by saying $ sudo mdadm /dev/md2 --add /dev/sdc1. This works fine, and mdadm confirms that the device has been re-added as follows: mdadm: re-added /dev/sdc1 After adding the device and allowing the array time to resynch, this is what the output of $ cat /proc/mdstat looks like: Personalities : [raid1] md3 : active raid1 sda4[0] sdb4[1] 244186840 blocks super 1.2 [2/2] [UU] md2 : active raid1 sdc1[0] sdd1[1] 732574464 blocks [2/2] [UU] md1 : active raid1 sda3[0] sdb3[1] 722804416 blocks [2/2] [UU] md0 : active raid1 sda1[0] sdb1[1] 6835520 blocks [2/2] [UU] unused devices: <none> Then after I reboot, this is what the output of $ cat /proc/mdstat looks like: Personalities : [raid1] md3 : active raid1 sda4[0] sdb4[1] 244186840 blocks super 1.2 [2/2] [UU] md2 : active raid1 sdd1[1] 732574464 blocks [2/1] [_U] md1 : active raid1 sda3[0] sdb3[1] 722804416 blocks [2/2] [UU] md0 : active raid1 sda1[0] sdb1[1] 6835520 blocks [2/2] [UU] unused devices: <none> During reboot, here is the output of $ sudo cat /var/log/syslog | grep mdadm : Jun 22 19:00:08 rook mdadm[1709]: RebuildFinished event detected on md device /dev/md2 Jun 22 19:00:08 rook mdadm[1709]: SpareActive event detected on md device /dev/md2, component device /dev/sdc1 Jun 22 19:00:20 rook kernel: [ 7819.446412] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.446415] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.446782] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.446785] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.515844] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.515847] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.606829] mdadm: sending ioctl 1261 to a partition! Jun 22 19:00:20 rook kernel: [ 7819.606832] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:48 rook kernel: [ 8027.855616] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:48 rook kernel: [ 8027.855620] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:48 rook kernel: [ 8027.855950] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:48 rook kernel: [ 8027.855952] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:49 rook kernel: [ 8027.962169] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:49 rook kernel: [ 8027.962171] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:49 rook kernel: [ 8028.054365] mdadm: sending ioctl 1261 to a partition! Jun 22 19:03:49 rook kernel: [ 8028.054368] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.588662] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.588664] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.601990] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.601991] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.602693] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.602695] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.605981] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.605983] mdadm: sending ioctl 1261 to a partition! Jun 22 19:10:23 rook kernel: [ 9.606138] mdadm: sending ioctl 800c0910 to a partition! Jun 22 19:10:23 rook kernel: [ 9.606139] mdadm: sending ioctl 800c0910 to a partition! Jun 22 19:10:48 rook mdadm[1737]: DegradedArray event detected on md device /dev/md2 Here is the result of $ cat /etc/mdadm/mdadm.conf: ARRAY /dev/md0 metadata=0.90 UUID=92121d42:37f46b82:926983e9:7d8aad9b ARRAY /dev/md1 metadata=0.90 UUID=9c1bafc3:1762d51d:c1ae3c29:66348110 ARRAY /dev/md2 metadata=0.90 UUID=98cea6ca:25b5f305:49e8ec88:e84bc7f0 ARRAY /dev/md3 metadata=1.2 name=rook:3 UUID=ca3fce37:95d49a09:badd0ddc:b63a4792 Here is the output of $ sudo mdadm -E /dev/sdc1 after re-adding the device and letting it resync: /dev/sdc1: Magic : a92b4efc Version : 0.90.00 UUID : 98cea6ca:25b5f305:49e8ec88:e84bc7f0 (local to host rook) Creation Time : Sun Jul 13 08:05:55 2008 Raid Level : raid1 Used Dev Size : 732574464 (698.64 GiB 750.16 GB) Array Size : 732574464 (698.64 GiB 750.16 GB) Raid Devices : 2 Total Devices : 2 Preferred Minor : 2 Update Time : Mon Jun 24 07:42:49 2013 State : clean Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Checksum : 5fd6cc13 - correct Events : 180998 Number Major Minor RaidDevice State this 0 8 33 0 active sync /dev/sdc1 0 0 8 33 0 active sync /dev/sdc1 1 1 8 49 1 active sync /dev/sdd1 Here is the output of $ sudo mdadm -D /dev/md2 after re-adding the device and letting it resync: /dev/md2: Version : 0.90 Creation Time : Sun Jul 13 08:05:55 2008 Raid Level : raid1 Array Size : 732574464 (698.64 GiB 750.16 GB) Used Dev Size : 732574464 (698.64 GiB 750.16 GB) Raid Devices : 2 Total Devices : 2 Preferred Minor : 2 Persistence : Superblock is persistent Update Time : Mon Jun 24 07:42:49 2013 State : clean Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 UUID : 98cea6ca:25b5f305:49e8ec88:e84bc7f0 (local to host rook) Events : 0.180998 Number Major Minor RaidDevice State 0 8 33 0 active sync /dev/sdc1 1 8 49 1 active sync /dev/sdd1 I also ran $ sudo smartctl -t long /dev/sdc and no hardware issues were detected. As long as I do not reboot, /dev/md2 seems to work fine. Does anyone have any suggestions?

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  • Various problems with software raid1 array built with Samsung 840 Pro SSDs

    - by Andy B
    I am bringing to ServerFault a problem that is tormenting me for 6+ months. I have a CentOS 6 (64bit) server with an md software raid-1 array with 2 x Samsung 840 Pro SSDs (512GB). Problems: Serious write speed problems: root [~]# time dd if=arch.tar.gz of=test4 bs=2M oflag=sync 146+1 records in 146+1 records out 307191761 bytes (307 MB) copied, 23.6788 s, 13.0 MB/s real 0m23.680s user 0m0.000s sys 0m0.932s When doing the above (or any other larger copy) the load spikes to unbelievable values (even over 100) going up from ~ 1. When doing the above I've also noticed very weird iostat results: Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 0.00 1589.50 0.00 54.00 0.00 13148.00 243.48 0.60 11.17 0.46 2.50 sdb 0.00 1627.50 0.00 16.50 0.00 9524.00 577.21 144.25 1439.33 60.61 100.00 md1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 md2 0.00 0.00 0.00 1602.00 0.00 12816.00 8.00 0.00 0.00 0.00 0.00 md0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 And it keeps it this way until it actually writes the file to the device (out from swap/cache/memory). The problem is that the second SSD in the array has svctm and await roughly 100 times larger than the second. For some reason the wear is different between the 2 members of the array root [~]# smartctl --attributes /dev/sda | grep -i wear 177 Wear_Leveling_Count 0x0013 094% 094 000 Pre-fail Always - 180 root [~]# smartctl --attributes /dev/sdb | grep -i wear 177 Wear_Leveling_Count 0x0013 070% 070 000 Pre-fail Always - 1005 The first SSD has a wear of 6% while the second SSD has a wear of 30%!! It's like the second SSD in the array works at least 5 times as hard as the first one as proven by the first iteration of iostat (the averages since reboot): Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 10.44 51.06 790.39 125.41 8803.98 1633.11 11.40 0.33 0.37 0.06 5.64 sdb 9.53 58.35 322.37 118.11 4835.59 1633.11 14.69 0.33 0.76 0.29 12.97 md1 0.00 0.00 1.88 1.33 15.07 10.68 8.00 0.00 0.00 0.00 0.00 md2 0.00 0.00 1109.02 173.12 10881.59 1620.39 9.75 0.00 0.00 0.00 0.00 md0 0.00 0.00 0.41 0.01 3.10 0.02 7.42 0.00 0.00 0.00 0.00 What I've tried: I've updated the firmware to DXM05B0Q (following reports of dramatic improvements for 840Ps after this update). I have looked for "hard resetting link" in dmesg to check for cable/backplane issues but nothing. I have checked the alignment and I believe they are aligned correctly (1MB boundary, listing below) I have checked /proc/mdstat and the array is Optimal (second listing below). root [~]# fdisk -ul /dev/sda Disk /dev/sda: 512.1 GB, 512110190592 bytes 255 heads, 63 sectors/track, 62260 cylinders, total 1000215216 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00026d59 Device Boot Start End Blocks Id System /dev/sda1 2048 4196351 2097152 fd Linux raid autodetect Partition 1 does not end on cylinder boundary. /dev/sda2 * 4196352 4605951 204800 fd Linux raid autodetect Partition 2 does not end on cylinder boundary. /dev/sda3 4605952 814106623 404750336 fd Linux raid autodetect root [~]# fdisk -ul /dev/sdb Disk /dev/sdb: 512.1 GB, 512110190592 bytes 255 heads, 63 sectors/track, 62260 cylinders, total 1000215216 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0003dede Device Boot Start End Blocks Id System /dev/sdb1 2048 4196351 2097152 fd Linux raid autodetect Partition 1 does not end on cylinder boundary. /dev/sdb2 * 4196352 4605951 204800 fd Linux raid autodetect Partition 2 does not end on cylinder boundary. /dev/sdb3 4605952 814106623 404750336 fd Linux raid autodetect /proc/mdstat root # cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sdb2[1] sda2[0] 204736 blocks super 1.0 [2/2] [UU] md2 : active raid1 sdb3[1] sda3[0] 404750144 blocks super 1.0 [2/2] [UU] md1 : active raid1 sdb1[1] sda1[0] 2096064 blocks super 1.1 [2/2] [UU] unused devices: Running a read test with hdparm root [~]# hdparm -t /dev/sda /dev/sda: Timing buffered disk reads: 664 MB in 3.00 seconds = 221.33 MB/sec root [~]# hdparm -t /dev/sdb /dev/sdb: Timing buffered disk reads: 288 MB in 3.01 seconds = 95.77 MB/sec But look what happens if I add --direct root [~]# hdparm --direct -t /dev/sda /dev/sda: Timing O_DIRECT disk reads: 788 MB in 3.01 seconds = 262.08 MB/sec root [~]# hdparm --direct -t /dev/sdb /dev/sdb: Timing O_DIRECT disk reads: 534 MB in 3.02 seconds = 176.90 MB/sec Both tests increase but /dev/sdb doubles while /dev/sda increases maybe 20%. I just don't know what to make of this. As suggested by Mr. Wagner I've done another read test with dd this time and it confirms the hdparm test: root [/home2]# dd if=/dev/sda of=/dev/null bs=1G count=10 10+0 records in 10+0 records out 10737418240 bytes (11 GB) copied, 38.0855 s, 282 MB/s root [/home2]# dd if=/dev/sdb of=/dev/null bs=1G count=10 10+0 records in 10+0 records out 10737418240 bytes (11 GB) copied, 115.24 s, 93.2 MB/s So sda is 3 times faster than sdb. Or maybe sdb is doing also something else besides what sda does. Is there some way to find out if sdb is doing more than what sda does? UPDATE Again, as suggested by Mr. Wagner, I have swapped the 2 SSDs. And as he thought it would happen, the problem moved from sdb to sda. So I guess I'll RMA one of the SSDs. I wonder if the cage might be problematic. What is wrong with this array? Please help!

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  • Site Review: MortgageCalculator.org - Forms Evaluation

    This site allows users to enter basic loan information into a form and when the user clicks the submit button the information is used to calculate a loan summary which includes: monthly payment, total interest paid, and the last payment date. This site uses server side validation and replaces any value not within a normal range with the calculator default for the form field. In addition, they also use server side code to calculate the items on the loan summary which is then displayed to the user. I personally think that by adding client side validation, it would improve the users experience because it would ensure that the data being submitted is within an acceptable norm and if the data entered was not within this range then it would allow the user to adjust the data.

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  • How do I list installed software with the installed size?

    - by Lewis Goddard
    I would like to have a list the installed software on my machine, with the disk space consumed by them alongside. I would prefer to be able to order by largest/smallest, but that is not a necessity. I am the sort of person who will install software to try it, and never clean up after myself. As a result, my 7GB (Windows and my Data are on separate partitions, as well as a swap area) Ubuntu 11.04 partition is suffering, and has started regularly showing warning messages. I have cleaned my browser cache, as well as everything under Package Cleaner in Ubuntu Tweak, and am left with 149.81 MB off free space.

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  • SQLAuthority News – My Evaluation of Singapore SharePoint Conference

    - by pinaldave
    Earlier this year I presented at SQLAuthority News – Presenting at South East Asia SharePoint Conference – Oct 26, 27, 2010 – Singapore. I felt very good to be presenting at Singapore as SharePoint Conference as I was the only SQL Speaker at the event. The event was filled with SharePoint enthusiasts and lots of other experts from all around the globe. The event was one of the best organized event, I attended in subcontinent. I just received my feedback score of the event. I was very much surprised and stunned. My ratting are very high as well, my demo were considered as one of the best demo of the whole event. I am not sure how much feedback I can share with community as organizer did not specify to me but I am very certain that I am allowed to share my own feedback. Speaker – 4.39 (best score 4.74, average 3.84) Contents – 4.37 (best score 4.39, average 3.65) Demo – 4.48 (best score, 4.48, average 3.61) I am very glad that all of my efforts to do presentations at SharePoint Conference are finally paid up. I was very much worried earlier if attendees will accept me or not as I am coming as speaker from foreign technology and no one knows me there. I must thank all of you for the same. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SharePoint, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Author Visit, T SQL, Technology Tagged: SharePoint

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  • Naming a class that decides to retrieve things from cache or a service + architecture evaluation

    - by Thomas Stock
    Hi, I'm a junior developer and I'm working on a pet project that I want to learn as much as possible from. I have the following scenario: There's a WCF service that I use to retrieve and update data, lets say Cars. So it's called CarWCFService and has a GetCars(), SaveCar(), ... . It implements interface ICarService. This isn't the Actual WCF service but more like a wrapper around it. Upon retrieving data from the service, I want to store them in local memory, as cache. I have made a class for this called CarCacheService which also implements interface ICarService. (I will explain later why it implements ICarService) I don't want client code to be calling these implementations. Instead, I want to create a third implementation for ICarService that tries to read from the CarCacheService before calling the WCFCarService, stores retrieved data in the CarCacheService, etc. 3 questions: How do I name this third class? I was thinking about something as simple as CarService. This does not really says what the service does exactly, tho. Is the naming for the other classes good? Would this naming and architecture be obvious for future programmers? This is my biggest concern. Does this architecture make sense? The reason that I implement ICarService on the CarCacheService is mainly because it allows me to fake the WCFService while debugging. I can store dummy data in a CarCacheService instance and pass it to the CarService, together with an(other) empty CarCacheService. If I made CacheCarService and WCFService public I could let client code decide if they want to drop the caching and just work directly on the WCFService.

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  • Any suggestions how it would be good to promote software in a small company ?

    - by Derfder
    Ok, I know if I am Red hat or other giant and offer some support etc. I can be profitable, in fact, Red Hat is doing quite well. However, what about a small company where I create a small program. e.g. an instant messenger for a windows or linux (just as an illustration) and I want to sell it. But how can I sell it if it is free and everybody can download it? Any advice? I like the idea of FSF by Richard Stallman, however I am missing the way how to sell my software under GNU/GPL licence. Any advice, how can I solve this problem? Any profitable small business software developers around with their opinion? Any links or names of small companies taht I can look at and study their model of business?

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  • What do I need to do, to get placed in any software company?

    - by Anto Aravinth
    I'm doing my 3rd year CSE Engineering. I guess this is the right time to ask this question! As in the next year, I'm going to do projects, "get my hands dirty". And there is only few days left out, as I know many people in Stack Overflow are working in Software field, I thought to ask these question. Does the project that I'm doing in my final year need to be excellent? If so, what kind of project to do? And how do you say that the project is excellent or not? Writing the code is very fun and serious at times. But the code should have a good algorithm? And mostly in any software companies interview, what kind of question they ask? Not but not the least, mastering in any particular language speaks in interviews?

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  • Microsoft sort une version d'évaluation de Windows Server 2008 R2 Hyper-V, sa solution de virtualisa

    Mise à jour du 30/03/10 Microsoft sort un ensemble de solutions pour la virtualisation dans Windows Server 2008 R2 Découvrez Windows Server 2008 R2 Hyper-V, System Center et Live Migration Microsoft semblait vouloir mettre les bouchées double dans la virtualisation du poste de travail aussi bien dans Windows 7 que dans Windows Server 2008 R2 (lire ci-avant). Il le confirme aujourd'hui en proposant de découvrir son nouvel ensemble de solutions de virtualisation pour ce dernier. Avec Hyper V, la virtualisation de serveur devient en effet une fonction de base de Windows Server 2008 R2. "Vous pouvez donc consolider sans surcoût vos serveurs phy...

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  • How Can Someone With Minimum Programming Experience Publish an App of an Existing Program not found in the Software Centre?

    - by Brenton Horne
    There's a free mathematics software that I would like to see in Ubuntu Software Centre, called, 'Sage.' I have minimal experience in programming, so I'm basically here asking if someone could either tell me how to accomplish this without said instructions being completely over my head or if someone could do it for me. For further information here's the sage homepage: http://sagemath.org/ and the .tar.lzma file for its installation is ~500MB and it takes around 2.2 GB on the HDD when installed, I found at least on 32 bit i386 Ubuntu 12.04 LTS. Any help will be greatly appreciated!

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  • What is the worst software bug in history? [closed]

    - by Amir Rezaei
    By having for example money and human suffering as the metric. What is the worst software bug in history? Note this is a specific question. Last month automaker Toyota announced a recall of 160,000 of its Prius hybrid vehicles following reports of vehicle warning lights illuminating for no reason, and cars' gasoline engines stalling unexpectedly. But unlike the large-scale auto recalls of years past, the root of the Prius issue wasn't a hardware problem -- it was a programming error in the smart car's embedded code. The Prius had a software bug.

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  • Site Review: Yahoo.com - Forms Evaluation

    Yahoo uses Ajax to suggest search terms to users when they are entering a search phrase into the search text box. Once the user has entered a search term and then presses the search button, the browser will post the search form to the search results page. I think that Yahoo is making great use of Ajax in this situation because they are helping users find information as well as suggesting alternative search terms for them to try based on what has already been added.

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  • One man software developer product success stories? [on hold]

    - by EugeneKr
    I've got a bad feeling that this question is not appropriate here.. Hopefully you can point me to the right place to ask such a thing (not google though, been there). I want to create my own product, but for some reason have no ideas, so decided to see what people have already done. I would like to start by myself too. I don't mind expanding, but at later stages when it is absolutely necessary. Anyway, to give you an example. There is a guy who created bingo card generation software, then somebody made a wedding planner software and they seem to be doing pretty fine. I would like to know more such cases to draw inspiration from. Do you know such people or maybe you are one of them? Also, if there are places on the net where they dwell, don't hesitate to tell me :) Thanks!

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