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• Jitter during wall collisions with Bullet Physics: contact/penetration tolerance?

  - by Niriel

  I use the bullet physics engine through Panda3d. My scene is still very simple, think 'Wolfenstein3d': tile-based, walls are solid cubes. I expect walls to block the player, and I expect the player to slide along the walls in case of non-normal incidence. What I get is what I expect, with one difference: there is some jitter. If I try to force myself into the wall, then I see the frames blinking quickly between two positions. These differ by about 0.04 units of distance, which corresponds to 4 cm in my game. I noticed a 4 cm elsewhere: the bottom of my player capsule is 4 cm below ground, when at rest. Does that mean that there is somewhere in the Bullet engine a default 0.04-units-long tolerance to differentiate contact from collision? If so, what should I do ? Should I change the scale of my game so that these 0.04 units correspond to 0.4 cm, making the jitter ten times smaller? Or can I ask bullet to change its tolerance to a smaller value? Edit This is the jitter I get: 6.155 - 6.118 = 0.036 LPoint3f(0, 6.11694, 0.835) LPoint3f(0, 6.15499, 0.835) LPoint3f(0, 6.11802, 0.835) LPoint3f(0, 6.15545, 0.835) LPoint3f(0, 6.11817, 0.835) LPoint3f(0, 6.15726, 0.835) LPoint3f(0, 6.11876, 0.835) LPoint3f(0, 6.15911, 0.835) LPoint3f(0, 6.11937, 0.835) I found a setMargin method. I set it to 5 mm both on the BoxShape for the walls and on the Capsule shape for the player. It still jitters by about 35 mm as illustrated by this log (11.117 - 11.082 = 0.035): LPoint3f(0, 11.0821, 0.905) LPoint3f(0, 11.1169, 0.905) LPoint3f(0, 11.082, 0.905) LPoint3f(0, 11.117, 0.905) LPoint3f(0, 11.082, 0.905) LPoint3f(0, 11.117, 0.905) LPoint3f(0, 11.0821, 0.905) LPoint3f(0, 11.1175, 0.905) LPoint3f(0, 11.0822, 0.905) LPoint3f(0, 11.1178, 0.905) LPoint3f(0, 11.0823, 0.905) LPoint3f(0, 11.1183, 0.905) The margin on the capsule did change my penetration with the floor though, I'm a bit higher (0.905 instead of 0.835). However, it did not change anything when colliding with the walls. How can I make the collisions against the walls less jittery? Edit, the day after: After more investigation, it appears that dynamic objects behave well. My problem comes from the btKinematicCharacterController that I use for moving my character; that stuff is totally bugged, according to the whole Internet :/.

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• Can someone explain the physical architecture of RAID 10 in complete layman's terms?

  - by Hank

  I am a newbie in the world of storage and I am having a hard time digesting the physical architecture of some of the RAID levels. I am particularly interested in RAID 10, and 50. I asked the question specifically about RAID 10, because I feel if I understand that, I'll understand the other. So, I get the definition of RAID 10 - "minimum 4 disks, a striped array whose segments are mirrored". If I've got 4 disks and Disks 1 and 2 are a mirrored pair, and Disks 3 and 4 are a mirrored pair - where does the data get striped? Thanks.

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• T-SQL select where and group by date

  - by bconlon

  T-SQL has never been my favorite language, but I need to use it on a fairly regular basis and every time I seem to Google the same things. So if I add it here, it might help others with the same issues, but it will also save me time later as I will know where to look for the answers!! 1. How do I SELECT FROM WHERE to filter on a DateTime column? As it happens this is easy but I always forget. You just put the DATE value in single quotes and in standard format: SELECT StartDate FROM Customer WHERE StartDate >= '2011-01-01' ORDER BY StartDate 2. How do I then GROUP BY and get a count by StartDate? Bit trickier, but you can use the built in DATEADD and DATEDIFF to set the TIME part to midnight, allowing the GROUP BY to have a consistent value to work on: SELECT DATEADD (d, DATEDIFF(d, 0, StartDate),0) [Customer Creation Date], COUNT(*) [Number Of New Customers] FROM Customer WHERE StartDate >= '2011-01-01' GROUP BY DATEADD(d, DATEDIFF(d, 0, StartDate),0) ORDER BY [Customer Creation Date] Note: [Customer Creation Date] and [Number Of New Customers] column alias just provide more readable column headers. 3. Finally, how can you format the DATETIME to only show the DATE part (after all the TIME part is now always midnight)? The built in CONVERT function allows you to convert the DATETIME to a CHAR array using a specific format. The format is a bit arbitrary and needs looking up, but 101 is the U.S. standard mm/dd/yyyy, and 103 is the U.K. standard dd/mm/yyyy. SELECT CONVERT(CHAR(10), DATEADD(d, DATEDIFF(d, 0, StartDate),0), 103) [Customer Creation Date], COUNT(*) [Number Of New Customers] FROM Customer WHERE StartDate >= '2011-01-01' GROUP BY DATEADD(d, DATEDIFF(d, 0, StartDate),0) ORDER BY [Customer Creation Date]  #

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• how to solve ArrayList outOfBoundsExeption?

  - by iQue

  Im getting: 09-02 17:15:39.140: E/AndroidRuntime(533): java.lang.IndexOutOfBoundsException: Invalid index 1, size is 1 09-02 17:15:39.140: E/AndroidRuntime(533): at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:251) when Im killing enemies using this method: private void checkCollision() { Rect h1 = happy.getBounds(); for (int i = 0; i < enemies.size(); i++) { for (int j = 0; j < bullets.size(); j++) { Rect b1 = bullets.get(j).getBounds(); Rect e1 = enemies.get(i).getBounds(); if (b1.intersect(e1)) { enemies.get(i).damageHP(5); bullets.remove(j); Log.d("TAG", "HERE: LOLTHEYTOUCHED"); } if (h1.intersect(e1)){ happy.damageHP(5); } if(enemies.get(i).getHP() <= 0){ enemies.remove(i); } if(happy.getHP() <= 0){ //end-screen !!!!!!! } } } } using this ArrayList: private ArrayList<Enemy> enemies = new ArrayList<Enemy>(); and adding to array like this: public void createEnemies() { Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.female); if (enemyCounter < 24) { enemies.add(new Enemy(bmp, this, controls)); } enemyCounter++; } I dont really understand what the problem is, Ive been looking around for a while but cant really find anything that helps me. If you know or if you can link me someplace where they have a solution for a similar problem Ill be a very happy camper! Thanks for ur time.

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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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• breaking mdadm raid and moving to NTFS

  - by daveyt

  I'm running Ubuntu 8 something and my data is on a mirrored pair of 1TB disks formatted as ext3, and the RAID is via mdadm. I want to move to Windows 7 (yeah yeah I know but Linux aint doing it for me at the moment) and migrate the disks to NTFS. My plan is: Break the MDADM RAID (by failing one disk logically) Format the 'failed' disk as NTFS Copy data from the RAID array to the NTFS disk (dont care about perms) Install Windows, (new separate non RAid disk) and my data disk is available. I've researched this and it seems the easiest way. I dont have another disk to back up to so I think this is my only way. Can anyone see a better/easier way?

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• OOP implementation of BUFFS and Stats. Suggestion

  - by Mattia Manzo Manzati

  I am developing an MMORPG server using NodeJS. I am not sure how to implement Buffs, i mean, equipped objects or used skills have effects on the Player() which has many Stats(), some of them have a max cap... Effects can change the Stat value, increasing or decreasing it by a value, a percentage or completly rewrite the value of the stat. After a while I have decided to create a base class for buffs, which can be hidden (if they are casted from an equipped object) or shown if they came from an ability (Spell). Anyway I need suggestion how to implement it, use an array for all active buffs for a stat and have a function calculate the value of the stat affected by buffs each time I need the value of the stat or...? Other more OOP's ways to do it? I have read this What's a way to implement a flexible buff/debuff system? but this implements only a percentage system, which buffs can only say "+10%, +20%, etc...", but I would love to have an hybrid system, which can have percentage values or static values (like WoW does), and using modifiers it's hard to implement, because modifiers refers to the current value of stat :/ Thanks for suggestions :)

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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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• Ubuntu 12.04 and Nvidia GTX 550 Ti

  - by Jim

  OK I'm currently trying to install Ubuntu x64 Server 12.04 onto the following machine: Intel Core i5-2320 3.0GHz LGA1155 6MB 8 GB DDR3 RAM, Gigabyte Z68P-DS3 S1155 Intel Z68 DDR3 ATX M/B, OCZ 60 GB SSD, 3x Samsung 2TB drives in a RAID 5 array (via M/B) Now what I think is causing the issue is the following: EVGA GeForce GTX 550 Ti 951MHz 1GB PCI-Express HDMI FPB As the server CD works in text mode I haven't had a problem with actually installing Ubuntu. Partioned with: 1GB /boot SSD, 59GB / SSD, 10GB swap RAID5, ~4TB /home RAID5 On a straight boot, you briefly see the GRUB menu, followed by a blank screen. The keyboard and mouse blink as they are initialised but no sign of life from the screen. Followed by a bit of research (otherwise known as google) ... Booted in quiet splash nomodeset Now I have a fully working linux distro at the command prompt. I then proceed to try and update the nvidia drivers with apt-get (after updating repositories etc) and rebooting. Still the same problem. I also tried reinstalling from the CD and installing said drivers in the install process before GRUB was installed, still the same symptoms. Does anybody have any solutions? I'm at my wits end here, I bought this machine to be a linux server / tinkering machine and have just spent 4-5 hours trying to just get a basic install working.

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• Ubuntu doesn't "see" external USB Hard Disk

  - by Mina Michael

  It's NTFS. It's USB2. I'm using Ubuntu 13.04. It works perfectly fine on Windows (which excludes cable and hardware problems). I have two Ubuntu computers and it's not detected on either. It's about 500 GB. Edits: Following the first link, I input sudo lsusb in a terminal; before and after connecting the HDD. The difference was Bus 001 Device 012: ID 14cd:6116 Super Top M6116 SATA Bridge. There it is! ("sata bridge" used to appear in a windows notification when I plugged in the HDD in!). ...This means that Ubuntu detects it but is it not mounting it? I tried this: sudo mount /dev/sdb1 /mnt But gives this: mount: special device /dev/sdb1 does not exist I also tried: sudo mount /dev/sdc1 /mnt but it stays with no output forever. I left it in background for about 30 min.s. sudo fdisk -l gives out this: Disk /dev/sda: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders, total 312581808 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: 0xa42d04a3 Device Boot Start End Blocks Id System /dev/sda1 63 80324 40131 de Dell Utility /dev/sda2 * 80325 102481919 51200797+ 7 HPFS/NTFS/exFAT /dev/sda3 263874558 312580095 24352769 5 Extended /dev/sda4 102481920 263872511 80695296 7 HPFS/NTFS/exFAT /dev/sda5 263874560 310505471 23315456 83 Linux /dev/sda6 310507520 312580095 1036288 82 Linux swap / Solaris Partition table entries are not in disk order Disk /dev/sdc: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders, total 976773168 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: 0x5822aaea Device Boot Start End Blocks Id System /dev/sdc1 2048 976769023 488383488 7 HPFS/NTFS/exFAT The part below "Partition table entries are not in disk order" takes about 5 minutes to appear. The outputs of ls /dev/ | grep sd before and after connecting the HDD: before: sda sda1 sda2 sda3 sda4 sda5 sda6 ,after: sda sda1 sda2 sda3 sda4 sda5 sda6 sdd sdd1 The second output has the lines sdd and sdd1 different from the first one. IT SHOWED THE FILES!! The command sudo mount /dev/sdd1 /mnt worked after I typed in sudo fdisk -l!!! Thanks a million!! :) :)

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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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• Profiling Startup Of VS2012 &ndash; Ants Profiler

  - by Alois Kraus

  I just downloaded ANTS Profiler 7.4 to check how fast it is and how deep I can analyze the startup of Visual Studio 2012. The Pro version which is useful does cost 445€ which is ok. To measure a complex system I decided to simply profile VS2012 (Update 1) on my older Intel 6600 2,4GHz with 3 GB RAM and a 32 bit Windows 7. Ants Profiler is really easy to use. So lets try it out. The Ants Profiler does want to start the profiled application by its own which seems to be rather common. I did choose Method Level timing of all managed methods. In the configuration menu I did want to get all call stacks to get full details. Once this is configured you are ready to go.   After that you can select the Method Grid to view Wall Clock Time in ms. I hate percentages which are on by default because I do want to look where absolute time is spent and not something else.   From the Method Grid I can drill down to see where time is spent in a nice and I can look at the decompiled methods where the time is spent. This does really look nice. But did you see the size of the scroll bar in the method grid? Although I wanted all call stacks I do get only about 4 pages of methods to drill down. From the scroll bar count I would guess that the profiler does show me about 150 methods for the complete VS startup. This is nonsense. I will never find a bottleneck in VS when I am presented only a fraction of the methods that were actually executed. I have also tried in the configuration window to also profile the extremely trivial functions but there was no noticeable difference. It seems that the Ants Profiler does filter away way too many details to be useful for bigger systems. If you want to optimize a CPU bound operation inside NUnit then Ants Profiler is with its line level timings a very nice tool to work with. But for bigger stuff it is certainly not usable. I also do not like that I must start the profiled application from the profiler UI. This makes it hard to profile processes which are started by some other process. Next: JetBrains dotTrace

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• Using the @ in SQL Azure Connections

  - by BuckWoody

  The other day I was working with a client on an application they were changing to a hybrid architecture – some data on-premise and other data in SQL Azure and Windows Azure Blob storage. I had them make a couple of corrections - the first was that all communications to SQL Azure need to be encrypted. It’s a simple addition to the connection string, depending on the library you use. Which brought up another interesting point. They had been using something that looked like this, using the .NET provider: Server=tcp:[serverName].database.windows.net;Database=myDataBase; User ID=LoginName;Password=myPassword; Trusted_Connection=False;Encrypt=True; This includes most of the formatting needed for SQL Azure. It specifies TCP as the transport mechanism, the database name is included, Trusted_Connection is off, and encryption is on. But it needed one more change: Server=tcp:[serverName].database.windows.net;Database=myDataBase; User ID=[LoginName]@[serverName];Password=myPassword; Trusted_Connection=False;Encrypt=True; Notice the difference? It’s the User ID parameter. It includes the @ symbol and the name of the server – not the whole DNS name, just the server name itself. The developers were a bit surprised, since it had been working with the first format that just used the user name. Why did both work, and why is one better than the other? It has to do with the connection library you use. For most libraries, the user name is enough. But for some libraries (subject to change so I don’t list them here) the server name parameter isn’t sent in the way the load balancer understands, so you need to include the server name right in the login, so the system can parse it correctly. Keep in mind, the string limit for that is 128 characters – so take the @ symbol and the server name into consideration for user names. The user connection info is detailed here: http://msdn.microsoft.com/en-us/library/ee336268.aspx Upshot? Include the @servername on your connection string just to be safe. And plan for that extra space…  

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• High load on a nagios server -- How many service checks for a nagios server is too many?

  - by Josh

  I have a nagios server running Ubuntu with a 2.0 GHz Intel Processor, a RAID10 array, and 400 MB of RAM. It monitors a total of 42 services across 8 hosts, most of which are checked using the check_http plugin even 5 minutes, some every minute. Recently the load on the nagios server has been above 4, often as high as 6. The server also runs cacti, gathering statistics every minute for 6 hosts. I wonder, how many services should hardware like this be able to handle? Is the load so high because I am pushing the limits of the hardware, or should this hardware be able to handle 42 service checks plus cacti? If the hardware is inadequate, should I look to add more RAM, more cores, or faster cores? What hardware / service checks are others running?

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• 5 ways to stop code thrashing&hellip;

  - by MarkPearl

  A few days ago I was programming on a personal project and hit a roadblock. I was applying the MVVM pattern and for some reason my view model was not updating the view when the state changed??? I had applied this pattern many times before and had never had this problem. It just didn’t make sense. So what did I do… I did what anyone would have done in my situation and looked to pass the blame to someone or something else. I tried to blame one of the inherited base classes, but it looked fine, then to Visual Studio, but it seemed to be fine and eventually to any random segment of code I came across. My elementary problem had now mushroomed into one that had lost any logical basis and I was in thrashing mode! So what to do when you begin to thrash? 1) Do a general code cleanup – Now there is a difference between cleaning code and changing code . When you thrash you change code and you want to avoid this. What you really want to do is things like rename variables to have better meaning and go over your comments. 2) Do a proof of concept – if cleaning code doesn’t help. The  you want to isolate the problem and identify the key concepts. When you isolate code you ideally want it to be in a totally separate project with as little complexity as possible. Make the building blocks and try and replicate the functionality that you are getting in your current application. 3) Phone a friend – I have found speaking to someone else about the problem generally helps me solve any thrashing issues I am having. Usually they don’t even have to say anything to solve the problem, just you talking them through the problem helps you get clarity of mind. 4) Let the dust settle – Sometimes time is the best solution. I have had a few problems that no matter who I discussed them with and no matter how much code cleaning I had done I just couldn’t seem to fix it. My brain just seemed to be going in circles. A good nights rest has always helped and often just the break away from the problem has helped me find a solution. 5) Stack overflow it – So similar to phone a friend. I am really surprised to see what a melting pot stack overflow has been and what a help it has been in solving technology specific problems. Just be considerate to those using the site and explain clearly exactly what problem you are having and the technologies you are using or else you will probably not get any useful help…

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• How do Unity 12.04/Compiz bindings really work?

  - by Daniel

  There is a bewildering array of places to set bindings, all inconsistent with one another. E.g. in Unity's System Settings having the Ctrl-key highlight the mouse position is an on/off choice. I like the feature, but not on such a prominent key where I keep activating it accidentally. The keyboard shortcuts allow only one binding per command, where I might like a convenient one on the external keyboard and an emergency alternative for when I'm on the road. Keyboard custom shortcuts has a nice interface, but allows only key bindings — besides it doesn't seem to work for me. So I activated CCSM Commands. There I have the choice of key-, mouse- and/or edge bindings. Whereas some places in CCSM offers only one or two of these binding possibilities, randomly at the whim of the programmer. I have not found a way to differentiate a mouse-drag from a click. E.g. I want <SuperMouse1-drag anywhere on a window to move it, while if I don't drag, it should be raise-lower. On the title bar I want the same without needing the <Super key. Now I find raise-lower only in System Settings where I can't assign a mouse binding. If therefore in CCSM I fallback to only lower and put move on the same binding, the window already gets lowered on mouse down, and I can then invisibly move it. Very useful! I have <Altasciicircum get in the way of an Emacs binding, with some to me useless popup overlay. I can find it nowhere, so I can't turn it off. So how can I go without these frontends until they have matured, and instruct Compiz directly, for example in the way Emacs or Sawfish have keymaps, and separate ones for each context, with inheritance?

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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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• 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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• Should I use a config file or database for storing business rules?

  - by foiseworth

  I have recently been reading The Pragmatic Programmer which states that: Details mess up our pristine code—especially if they change frequently. Every time we have to go in and change the code to accommodate some change in business logic, or in the law, or in management's personal tastes of the day, we run the risk of breaking the system—of introducing a new bug. Hunt, Andrew; Thomas, David (1999-10-20). The Pragmatic Programmer: From Journeyman to Master (Kindle Locations 2651-2653). Pearson Education (USA). Kindle Edition. I am currently programming a web app that has some models that have properties that can only be from a set of values, e.g. (not actual example as the web app data confidential): light-type = sphere / cube / cylinder The light type can only be the above three values but according to TPP I should always code as if they could change and place their values in a config file. As there are several incidents of this throughout the app, my question is: Should I store possibly values like these in: a config file: 'light-types' = array(sphere, cube, cylinder), 'other-type' = value, 'etc = etc-value a single table in a database with one line for each config item a database with a table for each config item (e.g. table: light_types; columns: id, name) some other way? Many thanks for any assistance / expertise offered.

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• Use Expressions with LINQ to Entities

  - by EltonStoneman

  [Source: http://geekswithblogs.net/EltonStoneman] Recently I've been putting together a generic approach for paging the response from a WCF service. Paging changes the service signature, so it's not as simple as adding a behavior to an existing service in config, but the complexity of the paging is isolated in a generic base class. We're using the Entity Framework talking to SQL Server, so when we ask for a page using LINQ's .Take() method we get a nice efficient SQL query for just the rows we want, with minimal impact on SQL Server and network traffic. We use the maximum ID of the record returned as a high-water mark (rather than using .Skip() to go to the next record), so the approach caters for records being deleted between page requests. In the paged response we include a HasMorePages indicator, computed by comparing the max ID in the page of results to the max ID for the whole resultset - if the latter is bigger, then there are more pages. In some quick performance testing, the paged version of the service performed much more slowly than the unpaged version, which was unexpected. We narrowed it down to the code which gets the max ID for the full resultset - instead of building an efficient MAX() SQL query, EF was returning the whole resultset and then computing the max ID in the service layer. It's easy to reproduce - take this AdventureWorks query:             var context = new AdventureWorksEntities();             var query = from od in context.SalesOrderDetail                         where od.ModifiedDate >= modified                          && od.SalesOrderDetailID.CompareTo(id) > 0                         orderby od.SalesOrderDetailID                         select od;   We can find the maximum SalesOrderDetailID like this:             var maxIdEfficiently = query.Max(od => od.SalesOrderDetailID);   which produces our efficient MAX() SQL query. If we're doing this generically and we already have the ID function in a Func:             Func<SalesOrderDetail, int> idFunc = od => od.SalesOrderDetailID;             var maxIdInefficiently = query.Max(idFunc);   This fetches all the results from the query and then runs the Max() function in code. If you look at the difference in Reflector, the first call passes an Expression to the Max(), while the second call passes a Func. So it's an easy fix - wrap the Func in an Expression:             Expression<Func<SalesOrderDetail, int>> idExpression = od => od.SalesOrderDetailID;             var maxIdEfficientlyAgain = query.Max(idExpression);   - and we're back to running an efficient MAX() statement. Evidently the EF provider can dissect an Expression and build its equivalent in SQL, but it can't do that with Funcs.

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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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• Nvidia driver overscan issue second monitor via dvi-d cable

  - by benmichael

  Ok, I know that I have a bit of a bizarre setup, but here goes. I have an old laptop, HP Pavilion 6000. The graphics card in there is a GeForce 7150M. The monitor connection is an old 18pin. The external monitor I use is a Samsung SyncMaster 2333. Don't ask me why, but this monitor only has a dvi-d connection (yes, i have searched it). So I have the monitor plugged into the laptop. If I use any of the Nvidia propriety drivers and try to set the resolution up to 1920x1080 (the monitor's native resolution), I get a massive overscan issue. Over the years I have tried to get this to work, tinkering with my xorg.conf to death. I have also tried this on every Ubuntu since 10.04, on all the corresponding LUbuntus, and on all the Linux Mints since Lisa. Exact same issue. I have even tried it in WinDoze and it works perfectly there (although I did get the error once, but was unable to reproduce it). Using the Open Source drivers it works perfectly iff I switch off the laptop monitor (this makes no difference with the Nvidia drivers). I would have happily gone on using the Open Source drivers, except that since upgrading to LUbuntu 12.10, the Open Source drivers make my monitor completely hazy and have the same overscan issue until I (through the haze, only because I know where things are) go to the monitor settings, activate the laptop's monitor, then deactivate it, and suddenly it comes right. I have to do this every time. So I have to find a way to fix one of them, so I may as well tackle the propriety drivers, hence this overlong question. Amidst other things, I have tried the nvidia-settings, but because it is connected to an 18pin, it detects the monitor as a vga monitor and does not give me overscan correction options. I have tried custom modlines (although there are always more of those try), I have tried using xrandr, and I have tried all the FlatPanelOptions. What I have not tried is a Gentoo build, as I don't have time any more to do that installation, but up to about three years ago when I ran Gentoo exclusively I did not have this issue. Below is an link to an image with a red highlight around the portion of the screen visible to me, the numbers around it are the number of pixels which are cut off. This does seem to drift a few pixels every now and then. Thanks in advance. Nvidia driver issue image

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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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• Applying DDD principles in a RESTish web service

  - by Andy

  I am developing an RESTish web service. I think I got the idea of the difference between aggregation and composition. Aggregation does not enforce lifecycle/scope on the objects it references. Composition does enforce lifecycle/scope on the objects it contain/own. If I delete a composite object then all the objects it contain/own are deleted as well, while the deleting an aggregate root does not delete referenced objects. 1) If it is true that deleting aggregate roots does not necessary delete referenced objects, what sense does it make to not have a repository for the references objects? Or are aggregate roots as a term referring to what is known as composite object? 2) When you create an web service you will have multiple endpoints, in my case I have one entity Book and another named Comment. It does not make sense to leave the comments in my application if the book is deleted. Therefore, book is a composite object. I guess I should not have a repository for comments since that would break the enforcement of lifecycle and rules that the book class may have. However I have URL such as (examples only): GET /books/1/comments POST /books/1/comments Now, if I do not have a repository for comments, does that mean I have to load the book object and then return the referenced comments? Am I allowed to return a list of Comment entities from the BookRepository, does that make sense? The repository for Book may eventually become rather big with all sorts of methods. Am I allowed to write JPQL (JPA queries) that targets comments and not books inside the repository? What about pagination and filtering of comments. When adding a new comment triggered by the POST endpoint, do you need to load the book, add the comment to the book, and then update the whole book object? What I am currently doing is having a own CommentRepository, even though the comments are deleted with the book. I could need some direction on how to do it correct. Since you are exposing not only root objects in RESTish services I wonder how to handle this at the backend. I am using Hibernate and Spring.

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• Permission to see the expandable list of ISA Server 2006

  - by Hossein Mobasher

  I am working on ISA Server 2006 in Windows Server. I want to add some policy rules to my server, I followed this link. But It points to In the Microsoft Internet Security and Acceleration Server 2006 management console, expand the array name, and then click the Firewall Policy node. When I open the ISA Server 2006 Management Console, I can not show the expand list, how can I force ISA to show the expandable tree to start Firewall Policy? Could any one please help me to do this ? Note : I have administrator permission for my account. Thanks in advance :)

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