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• Define a Policykit action for Upstart

  - by gentakojima

  I'm trying to get some user to start, stop and reload services by using the udev Upstart interface. I'm using Ubuntu 10.04. I created the file /usr/share/polkit-1/actions/com.ubuntu.Upstart0_6.Job.policy <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE policyconfig PUBLIC "-//freedesktop//DTD PolicyKit Policy Configuration 1.0//EN" "http://www.freedesktop.org/standards/PolicyKit/1.0/policyconfig.dtd"> <policyconfig> <vendor>UXITIC</vendor> <vendor_url>http://citius.usc.es/</vendor_url> <icon_name>gdm</icon_name> <action id="com.ubuntu.Upstart0_6.Job.Stop"> <_description>Stops a service</_description> <_message>Privileges are required to stop a service.</_message> <defaults> <allow_inactive>no</allow_inactive> <allow_active>auth_admin_keep</allow_active> </defaults> </action> </policyconfig> And also the corresponding authority file /etc/polkit-1/localauthority/50-local.d/10-allow-users-to-start-and-stop-services.pkla [Stop services] Identity=unix-user:jorge Action=com.ubuntu.Upstart_0.6.Job.Stop ResultAny=no ResultInactive=no ResultActive=auth_self But when I try to stop a service, I get Access Denied :( jorge$ dbus-send --print-reply --system --dest=com.ubuntu.Upstart /com/ubuntu/Upstart/jobs/ssh com.ubuntu.Upstart0_6.Job.Stop array:string:'' boolean:true Error org.freedesktop.DBus.Error.AccessDenied: Rejected send message, 1 matched rules; type="method_call", sender=":1.452" (uid=1021 pid=28234 comm="dbus-send) interface="com.ubuntu.Upstart0_6.Job" member="Stop" error name="(unset)" requested_reply=0 destination="com.ubuntu.Upstart" (uid=0 pid=1 comm="/sbin/init"))

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• Particle trajectory smoothing: where to do the simulation?

  - by nkint

  I have a particle system in which I have particles that are moving to a target and the new targets are received via network. The list of new target are some noisy coordinates of a moving target stored in the server that I want to smooth in the client. For doing the smoothing and the particle I wrote a simple particle engine with standard euler integration model. So, my pseudo code is something like that: # pseudo code class Particle: def update(): # do euler motion model integration: # if the distance to the target is more than a limit # add a new force to the accelleration # seeking the target, # and add the accelleration to velocity # and velocity to the position positionHistory.push_back(position); if history.length > historySize : history.pop_front() class ParticleEngine: particleById = dict() # an associative array # where the keys are the id # and particle istances are sotred as values # this method is called each time a new tcp packet is received and parsed def setNetTarget(int id, Vec2D new_target): particleById[id].setNewTarget(new_target) # this method is called each new frame def draw(): for p in particleById.values: p.update() beginVertex(LINE_STRIP) for v in p.positionHistory: vertex(v.x, v.y) endVertex() The new target that are arriving are noisy but setting some accelleration/velocity parameters let the particle to have a smoothed trajectories. But if a particle trajectory is a circle after a while the particle position converge to the center (a normal behaviour of euler integration model). So I decided to change the simulation and use some other interpolation (spline?) or smooth method (kalman filter?) between the targets. Something like: switch( INTERPOLATION_MODEL ): case EULER_MOTION: ... case HERMITE_INTERPOLATION: ... case SPLINE_INTERPOLATION: ... case KALMAN_FILTER_SMOOTHING: ... Now my question: where to write the motion simulation / trajectory interpolation? In the Particle? So I will have some Particle subclass like ParticleEuler, ParticleSpline, ParticleKalman, etc..? Or in the particle engine?

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• Raid 5 with 4 disks on Debian automatically creates a spare drive

  - by Razer

  I'm trying to to create a RAID 5 with 4x 2TB disks on Debian 6. I followed the instructions from: http://zackreed.me/articles/38-software-raid-5-in-debian-with-mdadm I created the raid with following command: sudo mdadm --create --verbose /dev/md0 --auto=yes --level=5 --raid-devices=4 /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1 After creating the RAID mdadm --detail /dev/md0 shows me: /dev/md0: Version : 1.2 Creation Time : Mon Jun 11 18:14:26 2012 Raid Level : raid5 Array Size : 5860535808 (5589.04 GiB 6001.19 GB) Used Dev Size : 1953511936 (1863.01 GiB 2000.40 GB) Raid Devices : 4 Total Devices : 4 Persistence : Superblock is persistent Update Time : Mon Jun 11 18:14:26 2012 State : clean, degraded Active Devices : 3 Working Devices : 4 Failed Devices : 0 Spare Devices : 1 Layout : left-symmetric Chunk Size : 512K Name : rsserver:0 (local to host rsserver) UUID : a68c3c99:1ef865e9:5a8a7bdc:64710ed8 Events : 0 Number Major Minor RaidDevice State 0 8 17 0 active sync /dev/sdb1 1 8 33 1 active sync /dev/sdc1 2 8 49 2 active sync /dev/sdd1 3 0 0 3 removed 4 8 65 - spare /dev/sde1 Why is there a spare drive? I didn't create one. I don't want to use a spare drive.

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• How to achieve selection of a tile from a tile sheet based on an ID?

  - by Bugster

  Let's say I have a tile sheet that contains 8 sprites per sheet. Each sprite is a tile of 30x30. I wrote my own custom map parser/map loader however I'm having trouble extracting a certain tile sprite from the file. I'll describe my problem better in order for everyone to understand. I wrote an enum of materials, each material has a value according to it's location relative to the tile sheet. For example void is 1, grass is 2, rock is 3, etc. So in my tile sheet they are represented as such: +---+---+---+---+---+ | 1 | 2 | 3 | 4 | 5 | +---+---+---+---+---+ Which is equivalent to: +------+-------+-------+ | void | grass | stone | +------+-------+-------+ Basically when rendering, I created a tile class, each tile has 2 coordinates: X and Y (They are calculated automatically) and a material which can be represented either as a number, either as a value (ID). When rendering, I have a vector of sprites which are all taken from 1 file called tilesheet.png, however each of them must only draw a certain portion of the tile sheet, for example say I have something like this: tile coordinateBounds(topLeftX, topLeftY, tileWidth, tileHeight); During the initialization of the map I calculate an array of tiles, and I give each of them their position, their materials based on the values in a map file and a few other variables such as collision. I need to apply the coordinateBounds to each of them according to their material value. For example if the material is grass it should only take the grass sprite from the tilesheet. I must also mention I'm using SFML, and there are no borders or spacing between the tiles.

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• CoffeeScript - inability to support progressive adoption

  - by Renso

  First if, what is CoffeeScript?Web definitionsCoffeeScript is a programming language that compiles statement-by-statement to JavaScript. The language adds syntactic sugar inspired by Ruby and Python to enhance JavaScript's brevity and readability, as well as adding more sophisticated features like array comprehension and pattern matching.The issue with CoffeeScript is that it eliminates any progressive adoption. It is a purist approach, kind of like the Amish, if you're not borne Amish, tough luck. So for folks with thousands of lines of JavaScript code will have a tough time to convert it to CoffeeScript. You can use the js2coffee API to convert the JavaScript file to CoffeeScript but in my experience that had trouble converting the files. It would convert the file to CoffeeScript without any complaints, but then when trying to generate the CoffeeScript file got errors with guess what: INDENTATION!Tried to convince the CoffeeScript community on github but got lots of push-back to progressive adoption with comments like "stupid", "crap", "child's comportment", "it's like Ruby, Python", "legacy code" etc. As a matter of interest one of the first comments were that the code needs to be re-designed before converted to CoffeeScript. Well I rest my case then :-)So far the community on github has been very reluctant to even consider introducing some way to define code-blocks, obviously curly braces is not an option as they use it for json object definitions. They also have no consideration for a progressive adoption where some, if not all, JavaScript syntax will be allowed which means all of us in the real world that have thousands of lines of JavaScript will have a real issue converting it over. Worst, I for one lack the confidence that tools like js2coffee will provide the correct indentation that will determine the flow of control in your code!!! Actually it is hard for me to find enough justification for using spaces or tabs to control the flow of code. It is no wonder that C#, C, C++, Java, all enterprise-scale frameworks still use curly braces. Have never seen an enterprise app built with Ruby or PhP.Let me know what your concerns are with CoffeeScript and how you dealt with large scale JavaScript conversions to CoffeeScript.

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• Where should "display functions" live in an MVC web app?

  - by User

  I'm using the Yii Framework which is an MVC php framework that is pretty similar to your standard web-based MVC framework. I want to display the related data from a many-to-many table as a list of strings in my view. Assuming a table schema like: tag { id, name } post { id, title, content, date } post_tag { post_id, tag_id } A post will display like: Date: 9/27/2012 Title: Some Title Content: blah blah blah... Tags: Smart Funny Cool Informative I can achieve this by doing something like this in my Post view: <?php echo join(' ', array_map(function($tag) { return $tag->name; }, $model->tags)); ?> (where $model->tags is an array of Tag objects associated with my model) My questions are: Is this amount of code/logic okay in the view? (Personally I think I'd rather just reference a property or call a single function.) If not, where should this code live? In the model? the controller? a helper? Potentially I may want to use in in other views as well. Ultimately I think its purely a display issue which would make me think it should be in the view, but then I have to repeat the code in any view I want to use it in.

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• Running Ubuntu Server from a USB key / thumb drive (being mindful of flash's write limitations)

  - by andybjackson

  Having become disillusioned with hacking Buffalo NAS devices, I've decided to roll my own home server. After some research, I have settled on an HP Proliant Microserver with Ubuntu Server and a ZFS RAID-Z array for data. I settled on this configuration after trying and regretfully rejecting FreeNAS because the Logitech Media Server (LMS) software isn't available on the AMD64 flavour of this platform and because I think Debian/Ubuntu server is a better future-proof platform. I considered Open Media Vault, but concluded that it isn't quite yet ready for my purposes. That said, FreeNAS does include the option to run itself off a 2GB+ flash device like USB key or thumb drive. Apparently FreeNAS is mindful of the write limitations of flash devices and so creates virtual disks for running the OS, writing only the required configuration information back to flash. This would give me an extra data drive slot. Q: Can Ubuntu Server be configured sensibly to run off a flash device such as a USB key/thumb drive? If so, how? The write limitations of flash should be accounted for.

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• Simple Ubuntu Server - Expanding disk space - adding a new drive LVM, RAID0 existing setup - how?

  - by NightWolf

  I have a 1TB ext4 partition mounted at / with all my data and Ubuntu 11.04 (natty) installed. Now this drive is almost full (I used it as a database server for some processing). RAID0 is ok, I can take a failure (touch wood). But I need a way to grow this partition. I have a new 1TB drive I want to add, however as my Ubuntu boot and all data is on the one partition I'm not sure how I can go about setting up a RAID0 or LVM array without loosing all my data. So the question is how can I extend my existing ext4 partition over two physical drives without losing data? Thanks!

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• Impossible to stop raid device

  - by Traroth

  I'm trying to stop a RAID disk in order to replace it by a new one, as this one is not working properly. I'm typing mdadm --stop /dev/md1, and I'm getting an error message: mdadm: fail to stop array /dev/md1: Device or resource busy I'm getting this message even if I reboot the server, and I can't see a process that could cause this. The server is working under a Debian with a 2.6.18-4-amd64 kernel. Could you help? Edit: Mote details about what my colleague tried out. After unmounting sda1, the command mdadm --remove /dev/md0 /dev/sda1 worked. But now, we still have an error message after mdadm --remove /dev/md1 /dev/sda5: mdadm: hot remove failed for /dev/sda5: Device or resource busy I still don't understand completly how the different partitions are mounted, so I suppose there is something I don't understand in the currenct situation...

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• SEO and external sites that serve responsive images (like Re-SRC)

  - by Baumr

  Re-SRC is a tool that allows you to automatically serve responsive images for your website from their cloud servers. It delivers a new image file each time the browser window (viewport) is resized. To use it in your HTML when linking to an image, you would do the following: <img src="http://app.resrc.it//www.your-domain.com/img/img001.jpg"/> Some more background for SEO considerations: As an example, looking at their demo page's code, the src of the Arc de Triomphe photo — when the browser window is resized to be at a tablet-width — shows this particular file at it's widest. It is found under the following URL: http://app4-uk.resrc.it/s=w560,pd1/ro=h//www.resrc.it/img/demo/demo-image-1.jpg If the viewport is increased to desktop-width, then a smaller image is served in line with the design; see this URL: http://app4-uk.resrc.it/s=w320,pd1/ro=h//www.resrc.it/img/demo/demo-image-1.jpg If I change the viewport to be about half-way between those two, then the image's URL is: http://app4-uk.resrc.it/s=w240,pd1/ro=h//www.resrc.it/img/demo/demo-image-1.jpg In other words, I found that there is a separate file for every 10-pixel increment of the image width. Very cool for saving bandwidth on mobile devices and service responsive/retina images on others, but... Here are two problems I see for SEO: The img on your site, part of your semantic markup, will not be hosted on your site at all, or even a server you control. Any links to these images will pass on "link juice" to Re-SRC's site instead. You are serving a vast array of different image files to different people — some may link to one, others to another size. Then there's the question of what different search engine crawlers will see. Also: There seems to be no fallback option if their servers are down. Do you see any other concerns? Or, perhaps, do you not see those as concerns?

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• What router settings to use for wireless home network

  - by Question Overflow

  While looking at the setting of my wireless router, I am bewildered by the array of options available. Despite searching on Wikipedia to try to understand the various acronyms, I am still clueless to decide what is the best setting to use although the default works fine. Rather than calling the internet service provider (ISP) to ask them the correct settings, I hope to learn more about the differences between some of the options listed below, so that I would be able to make a more informed decision from now onwards: PPPoE vs PPPoA LLC vs VC-Mux Bridge vs Routed In addition, I would also like to know the significance of the following MTU VPI VCI And whether or when I should manually specify DNS?

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• What are the essential considerations for setting up systems in a location with unreliable power?

  - by dunxd

  I deal with a lot of remote offices located in parts of the world where the local grid power supply is unreliable. Power can go off anytime with no warning, with outages ranging from minutes to days Power fluctuation is wild, with spikes and brown outs Currently the offices will have some or all of the following: A generator, with an inverter, or some sort of manual switch A big UPS or battery array connecting a number of devices Several smaller APC UPS with computers attached Low cost Voltage Regulators sometimes connected between mains and UPS or device. I know that each of these things needs to be appropriately rated for the equipment to which it is connected (although I am not sure how to calculate the correct rating). The offices will generally have the following equipment (in varying quantities): some sort of internet connection device (VSAT router, ADSL modem, WiMax router) Cisco ASA 5505 firewall a bunch of PCs printers one server I don't seek to replace the advice of an electrician, but in some of these locations they only answer the questions you ask them, so I need to make sure I have enough understanding of the essentials to protect equipment from damage, and possibly get through some power cuts.

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• Linux Live CD for old computer

  - by Joel Coehoorn

  I have a pentium II (that's right, pentium II) with a scant 200MB of ram. This was a high-end workstation in it's day. The machine currently runs dos on a raid array, and I need to pull some data from it. I figure my best chance at this is to use a linux live cd to copy the data to one of our active directory network shares (there is a network card in the machine). Unfortunately, my linux skills are abysmal, so I'm not sure where to get started: Where should I look to find a linux cd that will run well on such an old system Since I'm likely gonna need to be command-line only, what do I need to do to configure the network card and mount the network share via the command line? Bonus points: exact syntax needed to copy and convert the entire volume for use in VMware server 2.0, but really just copying all the data should be enough.

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• Android - Efficient way to draw tiles in OpenGL ES

  - by Maecky

  Hi, I am trying to write efficient code to render a tile based map in android. I load for each tile the corresponding bitmap (just one time) and then create the according tiles. I have designed a class to do this: public class VertexQuad { private float[] mCoordArr; private float[] mColArr; private float[] mTexCoordArr; private int mTextureName; private static short mCounter = 0; private short mIndex; As you can see, each tile has it's x,y location, a color array, texture coordinates and a texture name. Now, I want to render all my created tiles. To reduce the openGL api calls (I read somewhere that the state changes are costly and therefore I want to keep them to a minimum), I first want to hand ALL the coordinate-arrays, color-arrays and texture-coordinates over to OpenGL. After that I run two for loops. The first one iterates over the textures and binds the texture. The second for loop iterates over all Tiles and puts all tiles with the corresponding texture into an IndexBuffer. After the second for loop has finished, I call gl.gl_drawElements() whith the corresponding index buffer, to draw all tiles with the texture associated. For the next texture I do the same again. Now I run into some problems: Allocating and filling the FloatBuffers at the start of each rendering cycle costs very much time. I just run a test, where i wanted to put 400 coordinates into a FloatBuffer which took me about 200ms. My questions now are: Is there a better way, handling the coordinate and color structures? How is this correctly done, this is obviously not the optimal way? ;) thanks in advance, regards Markus

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• Terrible Performance with SATA Drives on Dell PowerEdge, steps to troubleshoot?

  - by Tom

  I had asked this question earlier and the question went missing so here it is again. Bought a DELL Poweredge 2950 to use as in-house QA Server. Disk performance is beyond terrible, 1000-4000 ms response time on the drive with our SQL Server database .mdf. Sql Server disk queue upwards of 300 at times. I'm a software guy, can anyone help me with steps to determine the issue? I don't know what RAID controller it has, how can I determine that? I'm speculating it could be BIOS issue. Perhaps the server used to have another kind of drive in it and when I added SATA the ??? buffer size is wrong??? Perhaps I chose wrong options (chose defaults) when setting up the RAID 1 arrays? I thought RAID 1 was a performance array?

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• Dell Powervault MD3000 - Not sharing Files between servers

  - by Kevin

  I'm a developer who has to set up a Dell Powervault MD3000 due to lack of resources. I have connected the Powervault to 2 Dell 2950 servers via the SAS cables. I performed the setup using Dell's MD Storage Manager software (4 disks, RAID 5 with hot spare). Then I added the disks using Windows 2003 disk management (Basic, not dynamic disk and formatted with NTFS). When I add files to the array from one server, they are not visible on the other server (and vice-versa). Is the error in the windows disk management configuration?

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• Convert uploaded video files to mp4 using PHP [closed]

  - by Subin

  I created a PHP video uploading script. I need to convert these files to mp4 for HTML5 VIDEO PLAYER using PHP while uploading . How can I do that ? Here is the PHP code. <?php if(isset($_POST['submit'])){ $user=$_COOKIE['VisitorName']; include('config.php'); session_start(); $session_id='1'; //$session id $path = "/home/simsu/subins/videos/data/videos/"; $valid_formats = array("wmv", "ogv", "mp4", "3gp", "ogg"); if(isset($_POST) and $_SERVER['REQUEST_METHOD'] == "POST") { $name = $_FILES['uploadedfile']['name']; $size = $_FILES['uploadedfile']['size']; if(strlen($name)) { list($txt, $ext) = explode(".", $name); if(in_array($ext,$valid_formats)) { if($size<(100024*100024)) { $actual_image_name = $path.time().".mp4"; $tmp = $_FILES['uploadedfile']['tmp_name']; $upurl="http://vtube.subins.com/files/video?vid=".time(); $title=$_POST['vn']; mysql_query("INSERT INTO videos(title,user,url,vid,ext) VALUES ('$title', '$user','$upurl',NOW(),'$ext')"); echo '<br><h1>'.$_FILES['uploadedfile']['name'] . " uploaded.</h1>"; } else echo "<br><h1>Video file size max 100 MB"; } else echo "<br><h1>Invalid file format.."; } else echo "<br><h1>Please select a video..!"; exit; } } ?>

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• RAID1: Migrate HDD to SSD?

  - by OMG Ponies

  My current workstation uses an Adaptec 5805, with Win2008 mirrored between two 72 GB (10K?) savvio drives. My question is if there's a way to migrate the mirror to use SSDs - I've been looking at 90GB Corsair Force (Sandy Bridge) to replace the existing setup. If it's possible, without installing the OS fresh. If I replaced the mirrored drive with an SSD, would the array sync the drives? Then I could promote the SSD mirror to be the primary, and use the second SSD as the mirror. That'd be too easy... Or should use Ghost to get an image of the existing setup, apply it to the SSD for a new mirror to be setup on?

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• Disable RAID Controller

  - by B.Mr.W.

  I have some decent HP Proliants server that come with "HP Smart Array P410i Controller" enabled, I am using these boxes to set up a Hadoop cluster and I know, RAID is for sure a no-no for Hadoop since the application itself will take care of data redundancy and extra intelligence provided by RAID won't be helpful and might turn down the performance. I tried to disable the devices at the BIOS and the box cannot even access the disk afterwards. So I am assuming the controller is sitting between disks and mother board, and we have to turn it on and configure it to "level0" or something like that. I am wondering what should I do to "disable" the RAID functionality so it will fit into the Hadoop environment.

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• Excel SUM From Different Sheets IF Date Found

  - by user329005

  I have a workbook with separate sheets for each product (about 20 sheets, adding more on a regular basis). Each product is only available for a certain time frame, and has daily sales data recorded on that product's sheet. I want an overall snapshot across all products from any given date to be consolidated on a new sheet. This would sum from a particular column on each of the other sheets if a corresponding date exists. I have a moderately passable function right now that has a separate VLOOKUP for each product sheet like SUM(IF(ISERROR(VLOOKUP(DATECELL,SHEETNAME!ARRAY,COLUMN... next VLOOKUP, next VLOOKUP etc., but it's incredibly cumbersome to update each function when a new product is added. I'm thinking there's a much easier way utilizing a named group (sheet names), SUMIF, VLOOKUP etc. Then when a new product sheet is added, I can simply add the sheet name to the named group rather than editing all the functions. Any help would be much appreciated!

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• choosing the right RAID level for PostgresQL database

  - by Sergey

  Hi, I got an disk array appliance of 8 disks 1T each (UltraStor RS8IP4). It will be used solely by PostgresQL database and I am trying to choose the best RAID level for it. The most priority is for read performance since we operate large data sets (tables, indexes) and we do lots of searches/scans. With the old disks that we have now the most slowdowns happen on SELECTs. Fault tolerance is less important, it can be 1 or 2 disks. Space is the least important factor. Even 1T will be enough. Which RAID level would you recommend in this situation. The current options are 60, 50 and 10, but probably other options can be even better.

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• Windows 7 file sharing password protecting or making stuff available to just me

  - by Carbonara

  Even with the new Homegroup feature I'm still finding the way Windows deals with folder sharing utterly baffling. Here's what I want to do. I have two computers, a PC Desktop and a laptop. I also live in a shared flat with other computer users. I have set up a Homegroup and a Workgroup on the desktop and joined them on the laptop and in the home group I have shared video, music and pictures. This is so that anyone on the network can view pictures and listen to music etc. But I want my Documents folder from my desktop to only be available to me on my laptop and not to anyone else that may be on the network. The Homegroup only allows (from what I can gather from the baffling array of options) sharing with everyone or no one. Is it possible to only allow the laptop to access the documents folder on the desktop? The user name and password are the same on both computers.

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• RAID1: Migrate HHD to SSD?

  - by OMG Ponies

  My current workstation uses an Adaptec 5805, with Win2008 mirrored between two 72 GB (10K?) savvio drives. My question is if there's a way to migrate the mirror to use SSDs - I've been looking at 90GB Corsair Force (Sandy Bridge) to replace the existing setup. If it's possible, without installing the OS fresh. If I replaced the mirrored drive with an SSD, would the array sync the drives? Then I could promote the SSD mirror to be the primary, and use the second SSD as the mirror. That'd be too easy... Or should use Ghost to get an image of the existing setup, apply it to the SSD for a new mirror to be setup on?

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• What is the recommended MongoDB schema for this quiz-engine scenario?

  - by hughesdan

  I'm working on a quiz engine for learning a foreign language. The engine shows users four images simultaneously and then plays an audio file. The user has to match the audio to the correct image. Below is my MongoDB document structure. Each document consists of an image file reference and an array of references to audio files that match that image. To generate a quiz instance I select four documents at random, show the images and then play one audio file from the four documents at random. The next step in my application development is to decide on the best document schema for storing user guesses. There are several requirements to consider: I need to be able to report statistics at a user level. For example, total correct answers, total guesses, mean accuracy, etc) I need to be able to query images based on the user's learning progress. For example, select 4 documents where guess count is 10 and accuracy is <=0.50. The schema needs to be optimized for fast quiz generation. The schema must not cause future scaling issues vis a vis document size. Assume 1mm users who make an average of 1000 guesses. Given all of this as background information, what would be the recommended schema? For example, would you store each guess in the Image document or perhaps in a User document (not shown) or a new document collection created for logging guesses? Would you recommend logging the raw guess data or would you pre-compute statistics by incrementing counters within the relevant document? Schema for Image Collection: _id "505bcc7a45c978be24000005" date 2012-09-21 02:10:02 UTC imageFileName "BD3E134A-C7B3-4405-9004-ED573DF477FE-29879-0000395CF1091601" random 0.26997075392864645 user "2A8761E4-C13A-470E-A759-91432D61B6AF-25982-0000352D853511AF" audioFiles [ 0 { audioFileName "C3669719-9F0A-4EB5-A791-2C00486665ED-30305-000039A3FDA7DCD2" user "2A8761E4-C13A-470E-A759-91432D61B6AF-25982-0000352D853511AF" audioLanguage "English" date 2012-09-22 01:15:04 UTC } 1 { audioFileName "C3669719-9F0A-4EB5-A791-2C00486665ED-30305-000039A3FDA7DCD2" user "2A8761E4-C13A-470E-A759-91432D61B6AF-25982-0000352D853511AF" audioLanguage "Spanish" date 2012-09-22 01:17:04 UTC } ]

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• a flexible data structure for geometries

  - by AkiRoss

  What data structure would you use to represent meshes that are to be altered (e.g. adding or removing new faces, vertices and edges), and that have to be "studied" in different ways (e.g. finding all the triangles intersecting a certain ray, or finding all the triangles "visible" from a given point in the space)? I need to consider multiple aspects of the mesh: their geometry, their topology and spatial information. The meshes are rather big, say 500k triangles, so I am going to use the GPU when computations are heavy. I tried using arrays with vertices and arrays with indices, but I do not love adding and removing vertices from them. Also, using arrays totally ignore spatial and topological information, which I may need studying the mesh. So, I thought about using custom double-linked list data structures, but I believe doing so will require me to copy the data to array buffers before going on the GPU. I also thought about using BST, but not sure it fits. Any help is appreciated. If I have been too fuzzy and you require other information feel free to ask.

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