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  • USB Drive Warm Boot Issue. Cold boot = Perfect. Warm boot = "No boot sector found on USB device"

    - by Dan
    I'm experiencing a boot/reboot quirk similar to, yet somewhat different from others posted here. I have two Western Digital "Passport" external USB2 drives (160GB and 320GB) with Ubuntu 11.10 installed. The BIOS on my laptop is set to boot USB drives before the internal drive, and it works well. Either drive will cold-boot Ubuntu 11.10 perfectly. However, at times the computer must be restarted (warm boot) to have software updates or other changes take effect. When I warm-boot the computer, the computer goes through its normal shutdown/restart, then the usual BIOS tests, at which time the USB drive is selected momentarily (as normal), and that's when the trouble starts. I get a "No boot sector found on USB device", and the computer proceeds to boot Windows from the internal drive. If I press F12 early during the restart sequence (allows manual selection of the boot sequence), USB is still shown before the internal drive on the sequence list (as it should be). If I highlight "USB" and press ENTER, I still get a "No boot sector..." error message, but the external USB drive then proceeds to boot Ubuntu normally. I have a third external USB drive (Western Digital 160 GB Media Center) that cold-boots and warm-boots perfectly, so I know everything in the computer is set up properly. It also tells me Ubuntu is set up correctly on the drives, as all three drives were done identically, and at the same time. I've tried formatting the Passport drives NTFS and FAT32, but it didn't change anything. If I power-down the computer, then start it up again, it will boot Ubuntu from either of the Passport drives perfectly - every time. It's as if during a warm boot the Passport drives are somehow looking for the boot loader in the wrong location on the drive - yet either drives works when booting from a cold start. Not a show-stopper .. but frustrating. Computer is a Dell XPS M1530, A12 BIOS (latest), but I don't think the computer plays into the issue because one of the three drives works at all times. It's only the two WD Passport models at issue here. Thanks!

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  • Deploying Data-Tier Applications of SQL Server 2008 R2

    SQL Server 2008 R2 Data-Tier Applications make database development, deployment and management much easier. When you create and build a Data Tier Application, it creates a single, self-contained unit of deployment called a DAC package. Arshad Ali shows you how to deploy the created DAC package and discusses the different methods of deployment. Free trial of SQL Backup™“SQL Backup was able to cut down my backup time significantly AND achieved a 90% compression at the same time!” Joe Cheng. Download a free trial now.

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  • Writing selenium tests, should I just get it done or get it right?

    - by Peter Smith
    I'm attempting to drive my user interface (heavy on javascript) through selenium. I've already tested the rest of my ajax interaction with selenium successfully. However, this one particular method seems to be eluding me because I can't seem to fake the correct click event. I could solve this problem by simply waiting in the test for the user to click a point and then continuing with the test but this seems like a cop out. But I'm really running out of time on my deadline to have this done and working. Should I just get this done and move on or should I spend the extra (unknown) amount of time to fix this problem and be able to have my selenium tests 100% automated?

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  • Ubuntu on USB does not boot on MacBook

    - by Sean H
    Ubuntu is installed on a 32 gigabyte flash-drive and it successfully booted every time up until I partitioned my hard-drive and installed Windows as a secondary boot (for programming reasons). Now every time I attempt to boot the Ubuntu flash-drive it boots into Windows XP. The same goes for partitions, I partitioned my hard-drive and installed Ubuntu and it only booted Windows XP. I am on a MacBook 6,1 with Mac OS X 10.6.8, 2 partitions, and I am using ReFit as my boot-loader. EDIT: I had Ubuntu working fine from FLASH DRIVE and at one point as a partition. I later uninstalled Ubuntu from my hard-drive and installed Windows. I then had to re-image my computer for certain reasons and I installed windows. Now when I attempt to boot anything other than Windows or OS X it boots into windows. Ubuntu was never on my hard drive while Ubuntu was on it. The flash-drive has been its own thing and has the boot-loader installed to it and loads from ReFit but boots into windows.

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  • Which Large File System Format to use for USB Flash drive compatible with Ubuntu/Mac/Windows?

    - by wajiw
    I've had this problem for a long time and can't find a solution. I switch between the 3 OSes all the time and use a 1TB USB Drive to do so. I can't seem to find a format that is compatible across all systems that handles large files (at least 8-9 GB). Does anyone have a solution for this? Recently I've tried exFat but that messes up the filesystem when trying to read on windows after adding files from Ubuntu (using the fuse driver). The OSes currently I'm using are Windows Vista/7, Mac OS X (10.6.5) and Ubuntu 10.10

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  • Smooth vector based jump

    - by Esa
    I started working on Wolfire's mathematics tutorials. I got the jumping working well using a step by step system, where you press a button and the cube moves to the next point on the jumping curve. Then I tried making the jumping happen during a set time period e.g the jump starts and lands within 1.5 seconds. I tried the same system I used for the step by step implementation, but it happens instantly. After some googling I found that Time.deltatime should be used, but I could not figure how. Below is my current jumping code, which makes the jump happen instantly. while (transform.position.y > 0) { modifiedJumperVelocity -= jumperDrag; transform.position += new Vector3(modifiedJumperVelocity.x, modifiedJumperVelocity.y, 0); } Where modifiedJumperVelocity is starting vector minus the jumper drag. JumperDrag is the value that is substracted from the modifiedJumperVelocity during each step of the jump. Below is an image of the jumping curve:

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  • High I/O wait after login

    - by Jackson Tan
    I've noticed that the ubuntuone-syncdaemon hogs up the hard disk every time I log in to Ubuntu (10.04). This takes up to two or three minutes, which makes Ubuntu insufferably slow. Opening Firefox is okay, but the browser is constantly greyed out and lags horribly. Given that I often shut down my laptop when I don't use it (about 3 to 4 times a day), this makes Ubuntu lose much of its lustre because of its long boot time. Is this a normal behaviour of Ubuntu One? Is it intended? Note that I've actually posted this in the forums here, but I received only few replies.

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  • Wifi problem in ubuntu using macbook pro when it restart

    - by Amro
    I was read that subject : http://ubuntuforums.org/showthread.php?t=2011756 and i follow it step by step in the page n 1 , then i was connect but after i restart my macbook again , i was lost the wifi connection.i dont know why or whats the problem exactly. every time I run this command: dmesg | grep -e b43 -e bcma I get this output: [ 2012.769684] bcma-pci-bridge 0000:02:00.0: PCI INT A -> GSI 17 (level, low) -> IRQ 17 [ 2012.769701] bcma-pci-bridge 0000:02:00.0: setting latency timer to 64 [ 2012.769775] bcma: Core 0 found: ChipCommon (manuf 0x4BF, id 0x800, rev 0x25, class 0x0) [ 2012.769808] bcma: Core 1 found: IEEE 802.11 (manuf 0x4BF, id 0x812, rev 0x1D, class 0x0) [ 2012.769889] bcma: Core 2 found: PCIe (manuf 0x4BF, id 0x820, rev 0x13, class 0x0) [ 2012.770175] bcma: PMU resource config unknown for device 0x4331 [ 2012.824527] bcma: Bus registered [ 2012.831744] b43-phy0: Broadcom 4331 WLAN found (core revision 29) [ 2013.371031] b43-phy0: Loading firmware version 666.2 (2011-02-23 01:15:07) and to get the connection again every time i must entery that code in the step of reload driver. How i can let the ubuntu see my wifi and wireless device automatically when i reboot my computer????

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  • What Counts For a DBA: Fitness

    - by Louis Davidson
    If you know me, you can probably guess that physical exercise is not really my thing. There was a time in my past when it a larger part of my life, but even then never in the same sort of passionate way as a number of our SQL friends.  For me, I find that mental exercise satisfies what I believe to be the same inner need that drives people to run farther than I like to drive on most Saturday mornings, and it is certainly just as addictive. Mental fitness shares many common traits with physical fitness, especially the need to attain it through repetitive training. I only wish that mental training burned off a bacon cheeseburger in the same manner as does jogging around a dewy park on Saturday morning. In physical training, there are at least two goals, the first of which is to be physically able to do a task. The second is to train the brain to perform the task without thinking too hard about it. No matter how long it has been since you last rode a bike, you will be almost certainly be able to hop on and start riding without thinking about the process of pedaling or balancing. If you’ve never ridden a bike, you could be a physics professor /Olympic athlete and still crash the first few times you try, even though you are as strong as an ox and your knowledge of the physics of bicycle riding makes the concept child’s play. For programming tasks, the process is very similar. As a DBA, you will come to know intuitively how to backup, optimize, and secure database systems. As a data programmer, you will work to instinctively use the clauses of Transact-SQL DML so that, when you need to group data three ways (and not four), you will know to use the GROUP BY clause with GROUPING SETS without resorting to a search engine.  You have the skill. Making it naturally then requires repetition and experience is the primary requirement, not just simply learning about a topic. The hardest part of being really good at something is this difference between knowledge and skill. I have recently taken several informative training classes with Kimball University on data warehousing and ETL. Now I have a lot more knowledge about designing data warehouses than before. I have also done a good bit of data warehouse designing of late and have started to improve to some level of proficiency with the theory. Yet, for all of this head knowledge, it is still a struggle to take what I have learned and apply it to the designs I am working on.  Data warehousing is still a task that is not yet deeply ingrained in my brain muscle memory. On the other hand, relational database design is something that no matter how much or how little I may get to do it, I am comfortable doing it. I have done it as a profession now for well over a decade, I teach classes on it, and I also have done (and continue to do) a lot of mental training beyond the work day. Sometimes the training is just basic education, some reading blogs and attending sessions at PASS events.  My best training comes from spending time working on other people’s design issues in forums (though not nearly as much as I would like to lately). Working through other people’s problems is a great way to exercise your brain on problems with which you’re not immediately familiar. The final bit of exercise I find useful for cultivating mental fitness for a data professional is also probably the nerdiest thing that I will ever suggest you do.  Akin to running in place, the idea is to work through designs in your head. I have designed more than one database system that would revolutionize grocery store operations, sales at my local Target store, the ordering process at Amazon, and ways to improve Disney World operations to get me through a line faster (some of which they are starting to implement without any of my help.) Never are the designs truly fleshed out, but enough to work through structures and processes.  On “paper”, I have designed database systems to catalog things as trivial as my Lego creations, rental car companies and my audio and video collections. Once I get the database designed mentally, sometimes I will create the database, add some data (often using Red-Gate’s Data Generator), and write a few queries to see if a concept was realistic, but I will rarely fully flesh out the database since I have no desire to do any user interface programming anymore.  The mental training allows me to keep in practice for when the time comes to do the work I love the most for real…even if I have been spending most of my work time lately building data warehouses.  If you are really strong of mind and body, perhaps you can mix a mental run with a physical run; though don’t run off of a cliff while contemplating how you might design a database to catalog the trees on a mountain…that would be contradictory to the purpose of both types of exercise.

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  • How to deal with Warning : "Uncommittable transaction is detected at the end of the batch. The trans

    - by VishnuTiwariBlog
    Hi, If you are integrating with SQL Server and dealing with batch messages, you may encounter this problem. And this is evitable. The reason is the contention of resources. If your batch contains four messages and all the four messages have to be updated to SQL Server and then at the same time four process will contend for SQL server table and resources and the obvious result will be, few of your transaction will be left uncomitted and if you are not handling dehydration [not modifying the default property of the Dehydration] then your orchestration will dehydrate and will go for retry. If retry is set for every five minutes then after five minutes Port will send the message to the database. Reason for writing this post was as I did not want to see so many DEHYDRATED messages. And this was happening as Host Throttling was not set. Thus as soon as the BizTalk Process finds that SQL resources are unavailable it will go and dehydrate that process and process will go for retry. The contension of resources is unavoidable though we can fine tune the Dehydration setting. If you increase the time that an orchestration can be blocked at a subscription before being dehydrated, possibly you will give more time BizTalk Engine to handle to SQL resource availability. At least I solve the problem by fine tuning the Dehydration properties. Below is the section of config info which you need to add to the BTSNTsvc.exe.config.   <?xml version="1.0" ?> <configuration>        <configSections>               <section name="xlangs" type="Microsoft.XLANGs.BizTalk.CrossProcess.XmlSerializationConfigurationSectionHandler, Microsoft.XLANGs.BizTalk.CrossProcess" />        </configSections>        <runtime>               <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">                      <probing privatePath="BizTalk Assemblies;Developer Tools;Tracking" />               </assemblyBinding>        </runtime>        <xlangs>               <Configuration>                      <Dehydration MaxThreshold="1800" MinThreshold="1" ConstantThreshold="-1">                             <VirtualMemoryThrottlingCriteria OptimalUsage="900" MaximalUsage="1300" IsActive="true" />                             <PrivateMemoryThrottlingCriteria OptimalUsage="50" MaximalUsage="350" IsActive="true" />                             <PhysicalMemoryThrottlingCriteria OptimalUsage="50" MaximalUsage="350" IsActive="false" />                      </Dehydration>               </Configuration>        </xlangs> </configuration>

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  • How do I cross-compile my application for Ubuntu 12.04 armhf architecture on a Ubuntu 12.04 i386 host?

    - by Jonathan Cave
    I have a large application I have written. I can successfully compile the application in the following scenarios: in a native compilation for the i386 host running Ubuntu 12.04 natively on a PandaBoard running Ubuntu 12.04 (this takes a long time) using Qemu and a chroot on the host PC for the armhf PandaBoard target (this takes a very long time) I would like to cross-compile the application on the i386 host to run on a target such as the PandaBoard to complete builds in a timely fashion. So far attempts made using the arm-linux-gnueabihf tool chain in the repositories has produced binaries that do not run correctly. At this stage, I have no plans to package the software. What is the recommended way to achieve a successful cross-compile?

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  • Why would you dual-run an app on Azure and AWS?

    - by Elton Stoneman
    Originally posted on: http://geekswithblogs.net/EltonStoneman/archive/2013/11/10/why-would-you-dual-run-an-app-on-azure-and-aws.aspxI had this question from a viewer of my Pluralsight course, Implementing the Reactive Manifesto with Azure and AWS, and thought I’d publish the response. So why would you dual-run your cloud app by hosting it on Azure and AWS? Sounds like a lot of extra development and management overhead. Well the most compelling reasons are reliability and portability. In 2012 I was working for a client who was making a big investment in the cloud, and at the end of the year we published their first external API for business partners. It was hosted in Azure and used some really nice features to route back into existing on-premise services. We were able to publish a clean, simple API to partners, and hide away the underlying complexity of the internal services while still leveraging them to do all the work. Two days after we went live, we were hit by the Azure SSL certificate expiry outage, and our API was unavailable for the best part of 3 days. Fortunately we had planned a gradual roll-out to partners, so the impact was minimal, but we’d been intending to ramp up quickly, and if the outage had happened a week or two later we would have been in a very bad place. Not least because our app could only run on Azure, we couldn’t package it up for another service without going back and reworking the code. More recently AWS had an issue with a networking device in one of their data centres which caused an outage that took the best part of a day to resolve. In both scenarios the SLAs are worthless, as you’ll get back a small percentage of your cloud expenditure, which is going to be negligible compared to your costs in dealing with the outage. And if your app is built specifically for AWS or Azure then if there’s an extended outage you can’t just deploy it onto a new set of kit from a different supplier. And the chances are pretty good there will be another extended outage, both for Microsoft and for Amazon. But the chances are small that it will happen to both at the same time. So my basic guidance has been: ignore the SLAs, go for better uptime by using two clouds. As soon as you need to scale beyond a single instance, start by scaling out to another cloud. Then scale out to different data centres in both clouds. Then you’ve got dual-cloud, quadruple-datacentre redundancy, so any more scaling you need can be left to the clouds to auto-scale themselves. By running in both clouds, you’ve made your app portable, so in the highly unlikely event that both AWS and Azure go down in multiple regions, you’ll have a deployment package which will let you spin up a new stack on yet another cloud, without having to rework your solution.

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  • Isolated Storage Made Easy

    In its most simple form Isolated Storage allows you to save name value pairs and retrieve them at some other time the next time your app runs. Granted we could get into XML and text files etc but I'm going to stick with just name value pairs. Lets take a look at this line:private void PresistKeyValue(string _Key, string _Value){StreamWriter MyWriter = new StreamWriter(new IsolatedStorageFileStream(_Key, FileMode.Create, IsolatedStorageFile.GetUserStoreForApplication()));MyWriter.Write(_Value);MyWriter.Close();}Nice...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • update-apt-xapian-index uses 100% CPU, even when Update Manager is set to not check for updates

    - by Dave M G
    I have a slightly older laptop running Ubuntu 11.10. It runs fine, but frequently, when I start it up, the CPU monitor in my Gnome Panel shows 100% usage for for what can be up to five minutes or so. It seems that the offending process is update-apt-xapian-index, which, if I understand correctly, is the update manager checking for updates. I have gone into the update manager settings, and selected to never check for updates. I'll do that manually when I feel like I have the time to leave the laptop running for that. However, despite my selection, this still happens. Roughly 50% of the time or more, when I start my laptop, it runs update-apt-xapian-index. How can I get the update manager to respect my settings, or at least to get this process to stop eating my CPU cycles?

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  • What will be a good python script (or your favorite language goes here) to test a system's performance and capabilities?

    - by dassouki
    Let's say you're in a computer store looking at 10 laptops, you want to really compare the system's capabilities. What will be an efficient "your fav language goes here" script that will allow you to do this? As an example, when I go to the store I usually open a macbook and a pro's terminal and write an equation in python, iterate it a million or so times, and time them. I like to compare the difference in time. What would be an ideal and simple script that can efficiently compare systems?

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  • Aren't there compilers better at telling the programmer what's wrong in a code ?

    - by jokoon
    I have worked a little while with the Microsoft compiler from Visual C++ but I worked a long time with G++, and I remember often having bad times understanding what was wrong in my code with the former. Beside binary code generation and optimisation, I think this is a very important feature of a C++ compiler: giving the programmer a clue that makes him understand as fast as possible what is wrong with his/her code. I can understand some programmers understand programming as some sort of "competition" to make less errors, but to me that's a counter productive opinion. I once tried Clang compiler for C from the LLVM thingie, I didn't use it for a long time, but I was impressed on how explicit and easy to understand the error messages were. What are your experiences, and how do you think this matters ? Some WIP of C++ Clang: http://clang.llvm.org/cxx_status.html

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  • Kicked out when logged in?

    - by acidzombie24
    When i log into ubuntu the screen goes black as it were logging in but then i am back in the login screen. I can login as guest (i should disable that). I can login via ssh. The last time i had no issues was when i used it this morning and the only unusual thing i did was shutdown via ssh (i think i wrote shutdown now) which had ubuntu hang after showing the shuting down screen for many seconds (i kind of assumed it shut down properly since the UI froze as well and it usually takes less time). Whats the easiest way to fix this w/o reinstalling? Its a brand new install and so it probably takes me 10mins to recopy/setup everything so i may just do that -edit- using 12.04

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  • Of transactions and Mongo

    - by Nuri Halperin
    Originally posted on: http://geekswithblogs.net/nuri/archive/2014/05/20/of-transactions-and-mongo-again.aspxWhat's the first thing you hear about NoSQL databases? That they lose your data? That there's no transactions? No joins? No hope for "real" applications? Well, you *should* be wondering whether a certain of database is the right one for your job. But if you do so, you should be wondering that about "traditional" databases as well! In the spirit of exploration let's take a look at a common challenge: You are a bank. You have customers with accounts. Customer A wants to pay B. You want to allow that only if A can cover the amount being transferred. Let's looks at the problem without any context of any database engine in mind. What would you do? How would you ensure that the amount transfer is done "properly"? Would you prevent a "transaction" from taking place unless A can cover the amount? There are several options: Prevent any change to A's account while the transfer is taking place. That boils down to locking. Apply the change, and allow A's balance to go below zero. Charge person A some interest on the negative balance. Not friendly, but certainly a choice. Don't do either. Options 1 and 2 are difficult to attain in the NoSQL world. Mongo won't save you headaches here either. Option 3 looks a bit harsh. But here's where this can go: ledger. See, and account doesn't need to be represented by a single row in a table of all accounts with only the current balance on it. More often than not, accounting systems use ledgers. And entries in ledgers - as it turns out – don't actually get updated. Once a ledger entry is written, it is not removed or altered. A transaction is represented by an entry in the ledger stating and amount withdrawn from A's account and an entry in the ledger stating an addition of said amount to B's account. For sake of space-saving, that entry in the ledger can happen using one entry. Think {Timestamp, FromAccountId, ToAccountId, Amount}. The implication of the original question – "how do you enforce non-negative balance rule" then boils down to: Insert entry in ledger Run validation of recent entries Insert reverse entry to roll back transaction if validation failed. What is validation? Sum up the transactions that A's account has (all deposits and debits), and ensure the balance is positive. For sake of efficiency, one can roll up transactions and "close the book" on transactions with a pseudo entry stating balance as of midnight or something. This lets you avoid doing math on the fly on too many transactions. You simply run from the latest "approved balance" marker to date. But that's an optimization, and premature optimizations are the root of (some? most?) evil.. Back to some nagging questions though: "But mongo is only eventually consistent!" Well, yes, kind of. It's not actually true that Mongo has not transactions. It would be more descriptive to say that Mongo's transaction scope is a single document in a single collection. A write to a Mongo document happens completely or not at all. So although it is true that you can't update more than one documents "at the same time" under a "transaction" umbrella as an atomic update, it is NOT true that there' is no isolation. So a competition between two concurrent updates is completely coherent and the writes will be serialized. They will not scribble on the same document at the same time. In our case - in choosing a ledger approach - we're not even trying to "update" a document, we're simply adding a document to a collection. So there goes the "no transaction" issue. Now let's turn our attention to consistency. What you should know about mongo is that at any given moment, only on member of a replica set is writable. This means that the writable instance in a set of replicated instances always has "the truth". There could be a replication lag such that a reader going to one of the replicas still sees "old" state of a collection or document. But in our ledger case, things fall nicely into place: Run your validation against the writable instance. It is guaranteed to have a ledger either with (after) or without (before) the ledger entry got written. No funky states. Again, the ledger writing *adds* a document, so there's no inconsistent document state to be had either way. Next, we might worry about data loss. Here, mongo offers several write-concerns. Write-concern in Mongo is a mode that marshals how uptight you want the db engine to be about actually persisting a document write to disk before it reports to the application that it is "done". The most volatile, is to say you don't care. In that case, mongo would just accept your write command and say back "thanks" with no guarantee of persistence. If the server loses power at the wrong moment, it may have said "ok" but actually no written the data to disk. That's kind of bad. Don't do that with data you care about. It may be good for votes on a pole regarding how cute a furry animal is, but not so good for business. There are several other write-concerns varying from flushing the write to the disk of the writable instance, flushing to disk on several members of the replica set, a majority of the replica set or all of the members of a replica set. The former choice is the quickest, as no network coordination is required besides the main writable instance. The others impose extra network and time cost. Depending on your tolerance for latency and read-lag, you will face a choice of what works for you. It's really important to understand that no data loss occurs once a document is flushed to an instance. The record is on disk at that point. From that point on, backup strategies and disaster recovery are your worry, not loss of power to the writable machine. This scenario is not different from a relational database at that point. Where does this leave us? Oh, yes. Eventual consistency. By now, we ensured that the "source of truth" instance has the correct data, persisted and coherent. But because of lag, the app may have gone to the writable instance, performed the update and then gone to a replica and looked at the ledger there before the transaction replicated. Here are 2 options to deal with this. Similar to write concerns, mongo support read preferences. An app may choose to read only from the writable instance. This is not an awesome choice to make for every ready, because it just burdens the one instance, and doesn't make use of the other read-only servers. But this choice can be made on a query by query basis. So for the app that our person A is using, we can have person A issue the transfer command to B, and then if that same app is going to immediately as "are we there yet?" we'll query that same writable instance. But B and anyone else in the world can just chill and read from the read-only instance. They have no basis to expect that the ledger has just been written to. So as far as they know, the transaction hasn't happened until they see it appear later. We can further relax the demand by creating application UI that reacts to a write command with "thank you, we will post it shortly" instead of "thank you, we just did everything and here's the new balance". This is a very powerful thing. UI design for highly scalable systems can't insist that the all databases be locked just to paint an "all done" on screen. People understand. They were trained by many online businesses already that your placing of an order does not mean that your product is already outside your door waiting (yes, I know, large retailers are working on it... but were' not there yet). The second thing we can do, is add some artificial delay to a transaction's visibility on the ledger. The way that works is simply adding some logic such that the query against the ledger never nets a transaction for customers newer than say 15 minutes and who's validation flag is not set. This buys us time 2 ways: Replication can catch up to all instances by then, and validation rules can run and determine if this transaction should be "negated" with a compensating transaction. In case we do need to "roll back" the transaction, the backend system can place the timestamp of the compensating transaction at the exact same time or 1ms after the original one. Effectively, once A or B visits their ledger, both transactions would be visible and the overall balance "as of now" would reflect no change.  The 2 transactions (attempted/ reverted) would be visible , since we do actually account for the attempt. Hold on a second. There's a hole in the story: what if several transfers from A to some accounts are registered, and 2 independent validators attempt to compute the balance concurrently? Is there a chance that both would conclude non-sufficient-funds even though rolling back transaction 100 would free up enough for transaction 117 (some random later transaction)? Yes. there is that chance. But the integrity of the business rule is not compromised, since the prime rule is don't dispense money you don't have. To minimize or eliminate this scenario, we can also assign a single validation process per origin account. This may seem non-scalable, but it can easily be done as a "sharded" distribution. Say we have 11 validation threads (or processing nodes etc.). We divide the account number space such that each validator is exclusively responsible for a certain range of account numbers. Sounds cunningly similar to Mongo's sharding strategy, doesn't it? Each validator then works in isolation. More capacity needed? Chop the account space into more chunks. So where  are we now with the nagging questions? "No joins": Huh? What are those for? "No transactions": You mean no cross-collection and no cross-document transactions? Granted - but don't always need them either. "No hope for real applications": well... There are more issues and edge cases to slog through, I'm sure. But hopefully this gives you some ideas of how to solve common problems without distributed locking and relational databases. But then again, you can choose relational databases if they suit your problem.

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  • Few questions about Thunderbird in Ubuntu 11.10

    - by Darwell
    I am happy with Ubuntu choice to replace Evolution with Thunderbird. However, I am having some issues with it. 1. What do you use to make Thunderbird minimize (and disappear from the launcher) when closing it? It should still be running (and give me notifications of new emails) but do not bother me on Launcher or in the list of windows, because I need free space. I tried using FireTray extension, it works quite okay, but it's buggy - sometimes there are two instances of Thunderbird open when using it and also, Thunderbird's global menu disappears after some time of using the extension. 2. Is there a plan to integrate Thunderbird's calendars into Date indicator in Ubuntu? I'd like to see my events when I have clicked on the time. Thanks.

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  • i need two gimps

    - by truth seeking fire walker
    i am using a vintage computer for my home use and to be frank i am satisfied with it since it is what i can afford now -- i use Ubuntu derived peer Linux OS and have gimp 2.8 working good and meets my needs. but due to the vintage configuration that i have it takes a long time to load and work but i need it for my little works related with educational helps - in most of the times i don't need my tweaked up gimp with all the plug ins and extra brushes i need a faster gimp so i want to have gimp 2.6 or even 2.4 in my system along with the current one. have pinta and like softwares but to meet my needs i definitely need gimp my question is can i have two different versions of gimp at the same time which i can load from the menu itself please help me thanking you all for allowing me breath the fresh air of open source --

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  • Don't Call it a Comeback

    - by Chris Haaker
    I received the email like most of you about Jeff and crew stepping down and selling the blog to another company. That it is a long time associate and friend of the team we have all grown to know and love, I feel much better about the move. Who cares, Chris, you haven't blogged religiously in ages! I know, and its a crime. Blame life, Twitter, my kids, laziness or whatever else you can think of. I always tell myself I am going to make a comeback - - "Don't call it a comeback - I been here for years." But after a few posts I seem to lose my steam. Its hard to explain, hell, I can't explain it. But we'll see what happens this time. Just don't call it a comeback.  2012 rMBP 15" Quad Core 2.33 GHz 16GB Memory 258GB SSDMarsEdit 3.5 (Please Microsoft Live Team - Make LiveWriter for OS X)

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  • Clock is Ticking for OBI 10g Supported Customers to move to OBI 11g

    - by Mike.Hallett(at)Oracle-BI&EPM
    Now is a perfect time for Partners to approach existing OBI 10g customers, to encourage and help them to upgrade to all the great new features in the current OBI v 11g; including the ability to go Mobile, to be in-memory on Exalytics, and to get tighter integration with Hyperion applications, Strategic Scorecards and Essbase. Oracle Lifetime Support Policy for Oracle BI Suite, version 10gR3, will end ‘normal’ support in July 2013. The final point release of Oracle Business Intelligence EE & Publisher 10gR3 was 10.1.3.4.x, which was generally available from July 2008 and will end “Premier Support” in July 2013.  From this time, customers may purchase “Extended Support” until July 2015, and from then “Sustaining Support”  indefinitely. For more information : Upgrade to Oracle Business Intelligence Enterprise Edition 11g, article on Technet Planning to Upgrade from Oracle BI 10g to BI 11g ?, at docs.oracle.com Oracle Business Intelligence Enterprise Edition 11g Oracle Lifetime Support Policy

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