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  • I don't know C. And why should I learn it?

    - by Stephen
    My first programming language was PHP (gasp). After that I started working with JavaScript. I've recently done work in C#. I've never once looked at low or mid level languages like C. The general consensus in the programming-community-at-large is that "a programmer who hasn't learned something like C, frankly, just can't handle programming concepts like pointers, data types, passing values by reference, etc." I do not agree. I argue that: Because high level languages are easily accessible, more "non-programmers" dive in and make a mess, and In order to really get anything done in a high level language, one needs to understand the same similar concepts that most proponents of "learn-low-level-first" evangelize about. Some people need to know C. Those people have jobs that require them to write low to mid-level code. I'm sure C is awesome. I'm sure there are a few bad programmers who know C. My question is, why the bias? As a good, honest, hungry programmer, if I had to learn C (for some unforeseen reason), I would learn C. Considering the multitude of languages out there, shouldn't good programmers focus on learning what advances us? Shouldn't we learn what interests us? Should we not utilize our finite time moving forward? Why do some programmers disagree with this? I believe that striving for excellence in what you do is the fundamental deterministic trait between good programmers and bad ones. Does anyone have any real world examples of how something written in a high level language--say Java, Pascal, PHP, or Javascript--truely benefitted from a prior knowledge of C? Examples would be most appreciated. (revised to better coincide with the six guidelines.)

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  • I don't know C. And why should I learn it?

    - by Stephen
    My first programming language was PHP (gasp). After that I started working with JavaScript. I've recently done work in C#. I've never once looked at low or mid level languages like C. The general consensus in the programming-community-at-large is that "a programmer who hasn't learned something like C, frankly, just can't handle programming concepts like pointers, data types, passing values by reference, etc." I do not agree. I argue that: Because high level languages are easily accessible, more "non-programmers" dive in and make a mess In order to really get anything done in a high level language, one needs to understand the same similar concepts that most proponents of "learn-low-level-first" evangelize about. Some people need to know C; those people have jobs that require them to write low to mid-level code. I'm sure C is awesome, and I'm sure there are a few bad programmers who know C. Why the bias? As a good, honest, hungry programmer, if I had to learn C (for some unforeseen reason), I would learn C. Considering the multitude of languages out there, shouldn't good programmers focus on learning what advances us? Shouldn't we learn what interests us? Should we not utilize our finite time moving forward? Why do some programmers disagree with this? I believe that striving for excellence in what you do is the fundamental deterministic trait between good programmers and bad ones. Does anyone have any real world examples of how something written in a high level language—say Java, Pascal, PHP, or Javascript—truely benefitted from a prior knowledge of C? Examples would be most appreciated.

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  • Poor home office network performance and cannot figure out where the issue is

    - by Jeff Willener
    This is the most bizarre issue. I have worked with small to mid size networks for quite a long time and can say I'm comfortable connecting hardware. Where you will start to lose me is with managed switches and firewalls. To start, let me describe my network (sigh, shouldn't but I MUST solve this). 1) Comcast Cable Internet 2) Motorola SURFboard eXtreme Cable Modem. a) Model: SB6120 b) DOCSIS 3.0 and 2.0 support c) IPv4 and IPv6 support 3-A) Cisco Small Business RV220W Wireless N Firewall a) Latest firmware b) Model: RV220W-A-K9-NA c) WAN Port to Modem (2) d) vlan 1: work e) vlan 2: everything else. 3-B) D-Link DIR-615 Draft 802.11 N Wireless Router a) Latest firmware b) WAN Port to Modem (2) 4) Servers connected directly to firewall a) If firewall 3-A, then vlan 1 b) CAT5e patch cables c) Dell PowerEdge 1400SC w/ 10/100 integrated NIC (Domain Controller, DNS, former DHCP) d) Dell PowerEdge 400SC w/ 10/100/1000 integrated NIC (VMWare Server) 4) Linksys EZXS88W unmanaged Workgroup 10/100 Switch a) If firewall 3-A, then vlan 2 b) 25' CAT5e patch cable to firewall (3-A or 3-B) c) Connects xBox 360, Blu-Ray player, PC at TV 5) Office equipment connected directly to firewall a) If firewall 3-A, then vlan 1 b) ~80' CAT6 or CAT5e patch cable to firewall (3-A or 3-B) c) Connects 1) Dell Latitude laptop 10/100/1000 2) Dell Inspiron laptop 10/100 3) Dell Workstation 10/100/1000 (Pristine host, VMWare Workstation 7.x with many bridged VM's) 4) Brother Laser Printer 10/100 5) Epson All-In-One Workforce 310 10/100 5-A) NetGear FS116 unmanaged 10/100 switch a) I've had this switch for a long time and never had issues. 5-B) NetGear GS108 unmanaged 10/100/1000 switch a) Bought new for this issue and returned. 5-C) Linksys SE2500 unmanaged 10/100/1000 switch a) Bought new for this issue and returned. 5-D) TP-Link TL-SG10008D unmanaged 10/100/1000 a) Bought new for this issue and still have. 6) VLan 1 Wireless Connections (on same subnet if 3-B) a) Any of those at 5c b) HP Laptop 7) VLan 2 Wireless Connection (on same subnet if 3-B) a) IPad, IPod b) Compaq Laptop c) Epson Wireless Printer Shew, without hosting a diagram I hope that paints a good picture. The Issue The breakdown here is at item 5. No matter what I do I cannot have a switch at 5 and have to run everything wireless regardless of router. Issues related to using a switch (point 5 above) SpeedTest is good. Poor throughput to other devices if can communicate at all. Usually cannot ping other devices even on the same switch although, when able, ping times are good. Eventual lose of connectivity and can "sometimes" be restored by unplugging everything for several days, not minutes or hours but we're talking a week if at all. Directly connect to computer gives good internet connection however throughput to other devices connected to firewall is at best horrible. Yet printing doesn't seem to be an issue as long as they are connected via wireless. I have to force the RV220W to 1000Mb on the respective port if using a Gig Switch Issues related to using wireless in place of a switch (point 5 above) Poor throughput to other devices if can communicate. SpeedTest is good. Bottom line Internet speeds are awesome. By the way, Comcast went WAY above and beyond to make sure it was not them. They rewired EVERYTHING which did solve internet drops. Computer to computer connections are garbage Cannot get switch at 5 to work, yet other at 4 has never had an issue. Direct connection, bypass switch, is good for DHCP and internet. DNS must be on server, not firewall. Cisco insists its my switches but as you can see I have used four and two different cables with the same result. My gut feeling is something is happening with routing. But I'm not smart enough to know that answer. I run a lot of VM's at 5-c-3, could that cause it? What's different compared to my previous house is I have introduced Gigabit hardware (firewall/switches/computers). Some of my computers might have IPv6 turned on if I haven't turned it off already. I'm truly at a loss and hope anyone has some crazy idea how to solve this. Bottom line, I need a switch in my office behind the firewall. I've changed everything. The real crux is I will find a working solution and, again, after days it will stop working. So this means I cannot isolate if its a computer since I have to use them. Oh and a solution is not throwing more money at this. I'm well into $1k already. Yah, lame.

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  • F# for the C# Programmer

    - by mbcrump
    Are you a C# Programmer and can’t make it past a day without seeing or hearing someone mention F#?  Today, I’m going to walk you through your first F# application and give you a brief introduction to the language. Sit back this will only take about 20 minutes. Introduction Microsoft's F# programming language is a functional language for the .NET framework that was originally developed at Microsoft Research Cambridge by Don Syme. In October 2007, the senior vice president of the developer division at Microsoft announced that F# was being officially productized to become a fully supported .NET language and professional developers were hired to create a team of around ten people to build the product version. In September 2008, Microsoft released the first Community Technology Preview (CTP), an official beta release, of the F# distribution . In December 2008, Microsoft announced that the success of this CTP had encouraged them to escalate F# and it is now will now be shipped as one of the core languages in Visual Studio 2010 , alongside C++, C# 4.0 and VB. The F# programming language incorporates many state-of-the-art features from programming language research and ossifies them in an industrial strength implementation that promises to revolutionize interactive, parallel and concurrent programming. Advantages of F# F# is the world's first language to combine all of the following features: Type inference: types are inferred by the compiler and generic definitions are created automatically. Algebraic data types: a succinct way to represent trees. Pattern matching: a comprehensible and efficient way to dissect data structures. Active patterns: pattern matching over foreign data structures. Interactive sessions: as easy to use as Python and Mathematica. High performance JIT compilation to native code: as fast as C#. Rich data structures: lists and arrays built into the language with syntactic support. Functional programming: first-class functions and tail calls. Expressive static type system: finds bugs during compilation and provides machine-verified documentation. Sequence expressions: interrogate huge data sets efficiently. Asynchronous workflows: syntactic support for monadic style concurrent programming with cancellations. Industrial-strength IDE support: multithreaded debugging, and graphical throwback of inferred types and documentation. Commerce friendly design and a viable commercial market. Lets try a short program in C# then F# to understand the differences. Using C#: Create a variable and output the value to the console window: Sample Program. using System;   namespace ConsoleApplication9 {     class Program     {         static void Main(string[] args)         {             var a = 2;             Console.WriteLine(a);             Console.ReadLine();         }     } } A breeze right? 14 Lines of code. We could have condensed it a bit by removing the “using” statment and tossing the namespace. But this is the typical C# program. Using F#: Create a variable and output the value to the console window: To start, open Visual Studio 2010 or Visual Studio 2008. Note: If using VS2008, then please download the SDK first before getting started. If you are using VS2010 then you are already setup and ready to go. So, click File-> New Project –> Other Languages –> Visual F# –> Windows –> F# Application. You will get the screen below. Go ahead and enter a name and click OK. Now, you will notice that the Solution Explorer contains the following: Double click the Program.fs and enter the following information. Hit F5 and it should run successfully. Sample Program. open System let a = 2        Console.WriteLine a As Shown below: Hmm, what? F# did the same thing in 3 lines of code. Show me the interactive evaluation that I keep hearing about. The F# development environment for Visual Studio 2010 provides two different modes of execution for F# code: Batch compilation to a .NET executable or DLL. (This was accomplished above). Interactive evaluation. (Demo is below) The interactive session provides a > prompt, requires a double semicolon ;; identifier at the end of a code snippet to force evaluation, and returns the names (if any) and types of resulting definitions and values. To access the F# prompt, in VS2010 Goto View –> Other Window then F# Interactive. Once you have the interactive window type in the following expression: 2+3;; as shown in the screenshot below: I hope this guide helps you get started with the language, please check out the following books for further information. F# Books for further reading   Foundations of F# Author: Robert Pickering An introduction to functional programming with F#. Including many samples, this book walks through the features of the F# language and libraries, and covers many of the .NET Framework features which can be leveraged with F#.       Functional Programming for the Real World: With Examples in F# and C# Authors: Tomas Petricek and Jon Skeet An introduction to functional programming for existing C# developers written by Tomas Petricek and Jon Skeet. This book explains the core principles using both C# and F#, shows how to use functional ideas when designing .NET applications and presents practical examples such as design of domain specific language, development of multi-core applications and programming of reactive applications.

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  • Very poor battery life on Lenovo ThinkPad W500 laptop

    - by Matt
    I have a new ThinkPad W500 laptop (w/ 9 cell battery) running Windows 7 RTM 64-bit. All drivers* and BIOS are the latest. Battery life appeared poor so I performed several tests under the following conditions: Battery starts with 100% charge Screen on minimum brightness Screen saver running Wifi n enabled and active "Normal" set of programs running including Outlook 2007, FeedDemon, TweetDeck and antivirus Laptop left untouched during tests Under the above conditions, I clocked under 2 hours of battery life across 3 tests (1:49, 1:52, 1:47). If I actually use the computer, we're looking at 1:30. Something is not right... The smoking gun here is that Lenovo hasn't officially released Windows 7 drivers for this laptop. I haven't tried with Vista or XP yet. What are others seeing? Update: For W500 owners w/ the 9 cell battery, what value do you see for "Full charge capacity" when on the Battery tab of the Power Manager utility? I see 81.87 Wh.

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  • Are you a good or bad programmer?

    - by Eli
    Hi All, I see a lot of questions on SO that are asked about 'good' programmers vs 'bad' programmers. For example, what is a good/bad programmer, how to tell a good/bad programmer, what to do about a bad programmer on a team, how to hire a good programmer. I know it's pretty easy to apply the words to other people, but I find myself wondering if anyone out there would actually define THEMSELVES in a Boolean fashion like this, rather than "good in some areas, weak in others..." I'm not asking as an either/or where you have to be one or the other, but as a 'both' - are you a good or bad programmer? If so (either one), why? Please note this isn't meant to be argumentative, or to define good/bad practices, etc. I just want to know how many people think they are good, bad, or neither out there.

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  • Extremely poor WiFi reception on new desktop

    - by guy
    I just received a new desktop with a built-in WiFi card (Windows 7 Home Premium x64). However, I am only able to receive any WiFi signal when the computer is within 1-2 meters of a router. Even then, the signal is very weak (Windows 7 says it is "poor"). I have tried this with 2 different routers and see similar results. I have somewhere around a dozen other devices that can connect to both routers with greater signal strength (usually full strength) from much, much further away. When I tried calling support I was instructed to reinstall my drivers and attempt to change the WiFi channel of the router. Neither worked. I was then told that the problem was with my routers and that the computer was functioning normally and that it was certainly not a hardware problem. What would be the cause of this and is there anything I can do to fix it?

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  • Poor TCP loopback throughput on Windows

    - by Yodan Tauber
    I measured the throughput of a locally bound TCP socket connection on my computer (Intel Q9550, 64 GB RAM, Windows XP 64 bit) using iperf. I got dissatisfying results (around 1.6 Gbit/s) each time, no matter how I tweaked the TCP settings (buffer length, window size, max segment size, no delay). I got similar results when I tried netperf. Now, I understand (from sources like these) that the average throughput of a loopback connection should be around 5 Gbit/s. What could be the reasons for such poor performance?

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  • Are highly capable programmers paid more than their managers?

    - by Fun Mun Pieng
    I know a lot of programmers are paid less than their managers by significant amounts, as highlighted there. How often is it that a programmer gets paid more than his manager? Or phrased different how many programmers are paid more than their managers? Personally, I know of one case. I'm asking to see how common is the case. When I say "manager", I mean anyone further up their organization hierarchy.

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  • is good for one year experince Java Developer to do VB.NET development?

    - by tanghao
    I'm a java programmer with around one and half years experience. Recently my boss wants me to develop an excel add-in with VB.NET in next a few months or maybe I have to be fully in charge of this add-in in the further. It makes me quite nervous right now because I am really not sure what this VB.NET development experience could mean to me in the further as I am not so sure if it's good to diverse my experience in current stage. Any one could give some helps and suggestions?

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  • Poor NFS Performance: OpenFiler

    - by Safin09
    Good Day Everyone, I have an issue with OpenFiler, a Linux-based operating that converts a computer system into a SAN/NAS appliance. Here is the problem. In my environment we have two Netapp Storevault 500 appliances that I normally perform backups to a NFS share. There are two backup cronjobs that use ghettoVCB to backup two groups of VM's. One group is a pool of 3 VMs. This takes 13 mins to complete. A second job that backups a pool of 5 VMs to a 2nd Storevault appliance which takes 2 hours. We then installed Openfiler on a old server that has 2 core Xeon processors. There is a software RAID 5 process in place. When performing the same backups to a NFS Openfiler share, the first backup job, which takes 13 mins, takes around 4 hours. The second backup job, which takes 2 hours, takes almost 10 hours to complete. This is unacceptable!!!! Especially considering the strain placed on the host ESX Server. I assumed that because of the software RAID 5, the overhead on the CPU explained the long backup times. I then installed Openfiler on a 2nd server, an IBM x306 machine which has a P4 Intel processor. This time no software RAID or any RAID at all. A single 750GB hard drive that contained the OS and the rest of the disk uses to backup VMs to a NFS share. I performed the first backup job of the pool of 3 VMs. This time the backup job took 1 and 1/2 hours to complete instead of 13 mins!!!!!!!!!! Is Openfiler simply poor at being an NFS Server!!!!!!!!!!!!! Has anyone else had these issues with Openfiler?

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  • Poor gaming performance with hyper-v installed in windows 8

    - by SnowCrash
    I am getting very poor gaming performance on my Windows 8 host OS with Hyper-V installed but no guest machines running. For example World of Tanks reports 60-70 FPS without Hyper-V installed and 4-14 FPS with it installed. A similar, dramatic, hit is observed in several other games so the issue is not WoT specific. To make the point clear, I am not trying to run games in a virtual machine. I don't even have a VM running while observing this effect. I simply have the Hyper-V feature installed. My system specs: AMD Phenom II 965 (3.4 GHz) AMD Radeon 6950 2GB (XFX Double D HD-695X-CDFC) 16GB DDR3 1333 AMD 790GX chipset Mainboard (Gigabyte GA-MA790GPT-UD3H) I have tried every AMD driver from 12.8 to the current 12.11beta8, virtualization is enabled in the BIOS settings, the onboard 3300HD video device is disabled in BIOS and I have read the MSDN blog entry here regarding a similar issue in Server 2008 that was resolved in 2008 R2 (and hopefully not regressed in Win 8). I'd like to be able to use Hyper-V for development and testing at home (I am a sysadmin/software developer professionally). If, however, I can't also use my home system for entertainment I'll have to scrap those plans.

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  • My EliteBook is not auto picking 1080p for external monitor, poor display on forcing

    - by Griever
    I'm connecting my Samsung LED S22A300B to my HP EliteBook 6930p through VGA out. Laptop has Intel 4500MHD video card. I have latest drivers installed for both card and monitor. Only 800x600 and 1024x768 are shown. A lot of other people get this problem when they use it with docking station as discussed here. But I am not using any docking station. The monitor works great with my desktop though. As advised on the aforementioned page, one of the things I tried was to force the resolution using Intel's "custom resolution" feature. I installed PowerStrip on my desktop and copied advanced timing values(front/back porch,sync width, etc.) from there and then used the same values while defining a custom resolution in my laptop's Intel graphics utility. As a result, I got the 1080p resolution but the display is poor. Text has some weird colored shadow and sometimes on images too. What should I do?

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  • Poor Write Performance in VM inside Proxmox PVE 2.0

    - by sorsenne
    I am running a PVE 2.0 on a decent Hardware (2 SATA HDDs as RAID1, 12GB RAM, i7 CPU) but the I/O Performance is very poor inside the VM (Ubuntu 11.10 Server). The very same VM was copied to another Server running simply Ubuntu Server with KVM and had better I/O Perf. this is how the HDD is shown in the Guest: ata1: SATA link up 6.0 Gbps (SStatus 133 SControl 300) ata1.00: ATA-8: ST3000DM001-9YN166, CC49, max UDMA/133 ata1.00: 5860533168 sectors, multi 16: LBA48 NCQ (depth 31/32), AA ata1.00: configured for UDMA/133 scsi 0:0:0:0: Direct-Access ATA ST3000DM001-9YN1 CC49 PQ: 0 ANSI: 5 sd 0:0:0:0: [sda] 5860533168 512-byte logical blocks: (3.00 TB/2.72 TiB) sd 0:0:0:0: [sda] 4096-byte physical blocks sd 0:0:0:0: [sda] Write Protect is off sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00 sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA I tested with DD: $ dd bs=1M count=128 if=/dev/zero of=test conv=fdatasync 128+0 records in 128+0 records out 134217728 bytes (134 MB) copied, 19.2222 s, 7.0 MB/s on the Host, this same Test will result with 156 MB/s in average. PS: I am using VirtIO and see no error in dmesg.

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  • Very poor SCSI hd performance on IBM x336 with LSI 1030 RAID1

    - by David Tschoepe
    I'm experiencing very poor performance on an IBM x336 server with dual 73GB 15k hard drives on a U320 controller, LSI 1030. We're getting maybe 3.5MB/sec max (per HD Tune utility). It should be over 100MB/sec at least, I would think (another x335 box is running 70-80MB/sec). The server was recently setup and didn't really notice the problem, but may have been there from the beginning, so not sure. I have installed the IBM ServerRAID Windows utility. The server is running Windows 2008 R2 Web edition (if that matters). I thought maybe one of the drives was bad, so far I have removed one of the drives out of the array and tested again, but still the same results. I'm waiting for the RAID1 to resync and I will try pulling the other drive next. I've also used the ServerRAID utility but haven't noticed anything in there that might indicate a problem. Not sure if I'm on the right path here. So looking for some advice to track this down.

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  • Poor write performance on Debian server running NFS with 22TB exported JFS filesystem

    - by user143546
    I am currently running a debian server that is exporting a large JFS filesystem (22TB) over NFS (nfs-kernel-server.) When attempting to write to the NFS share, the performance is very poor. The 22TB disk is sitting on a NAS mounted using iSCSI. It will bust for a moment near expected line speed, and then sit idle for several seconds. Very little traffic measured in the low kb/sec. The wait peeks on write. When reading from the NFS mount, the system operates at expected speeds (11MB/sec). The issue does not occur when using SFTP, rsync, or local coping (non-nfs). The issue persists between stable and testing releases. On the same machine I have a 14TB ext4 filesystem using the exact same export configuration that does not share the issue. This share is not in regular use and thus not consuming resources. NFS Server: cat /etc/exports /data2 10.1.20.86(rw,no_subtree_check,async,all_squash) cat /sys/block/sdb/queue/scheduler noop [deadline] cfq cat /etc/default/nfs-kernel-server RPCNFSDCOUNT=8 RPCNFSDPRIORITY=0 RPCMOUNTDOPTS=--manage-gids NEED_SVCGSSD= RPCSVCGSSDOPTS= NFS Client: cat /etc/fstab 10.1.20.100:/data2 /root/incoming nfs rw,noatime,soft,intr,noacl 0 2 cat /sys/block/sdb/queue/scheduler noop [deadline] cfq cat /proc/mounts 10.1.20.100:/data2/ /root/incoming nfs4 rw,noatime,vers=4,rsize=262144,wsize=262144,namlen=255,soft,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=10.1.20.86,minorversion=0,addr=10.1.20.100 0 0 This problem has me pretty stumped. Any help would be greatly welcomed. Thanks.

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  • Very poor read performance compared to write performance on md(raid1) / crypt(luks) / lvm

    - by Android5360
    I'm experiencing very poor read performance over raid1/crypt/lvm. In the same time, write speeds are about 2x+ faster on the same setup. On another raid1 setup on the same machine I get normal read speeds (maybe because I'm not using cryptsetup). OS related disks: sda + sdb. I have raid1 configuration with two disks, both are in place. I'm using LVM over the RAID. No encryption. Both disks are WD Green, 5400 rpm. IO test results on this raid1: dd if=/dev/zero of=/tmp/output.img3 bs=8k count=256k conv=fsync - 2147483648 bytes (2.1 GB) copied, 22.3392 s, 96.1 MB/s sync echo 3 > /proc/sys/vm/drop_caches dd if=/tmp/output.img3 of=/dev/null bs=8k - 2147483648 bytes (2.1 GB) copied, 15.9 s, 135 MB/s And here is the problematic setup (on the same machine). Currently I have only one sdc (WD Green, 5400rpm) configured in software raid1 + crypt (luks, serpent-xts-plain) + lvm. Tomorrow I will attach another disk (sdd) to complete this two-disk raid1 setup. IO tests results on this raid1: dd if=/dev/zero of=output.img3 bs=8k count=256k conv=fsync 2147483648 bytes (2.1 GB) copied, 17.7235 s, 121 MB/s sync echo 3 > /proc/sys/vm/drop_caches dd if=output.img3 of=/dev/null bs=8k 2147483648 bytes (2.1 GB) copied, 36.2454 s, 59.2 MB/s We can see that the read performance is very very bad (59MB/s compared to 135MB/s when using no encryption). Nothing is using the disks during benchmark. I can confirm this because I checked with iostat and dstat. Details on the hardware: disks: all are WD green, 5400rpm, 64mb cache. cpu: FX-8350 at stock speed ram: 4x4GB at 1066Mhz. Details on the software: OS: Debian Wheezy 7, amd64 mdadm: v3.2.5 - 18th May 2012 LVM version: 2.02.95(2) (2012-03-06) LVM Library version: 1.02.74 (2012-03-06) LVM Driver version: 4.22.0 cryptsetup: 1.4.3 Here is how I configured the slow raid1+crypt+lvm setup: parted /dev/sdc mklabel gpt type: ext4 start: 2048s end: -1 Now the raid, crypt and the lvm configuration: mdadm --create /dev/md1 --level=1 --raid-disks=2 missing /dev/sdc cryptsetup --cipher serpent-xts-plain luksFormat /dev/md1 cryptsetup luksOpen /dev/md1 md1_crypt vgcreate vg_sql /dev/mapper/md1_crypt lvcreate -l 100%VG vg_sql -n lv_sql mkfs.ext4 /dev/mapper/vg_sql-lv-sql mount /dev/mapper/vg_sql-lv_sql /sql So guys, can you help me identify the reason and fix it? It has to be something with the cryptsetup as there is no such read slowdown on the other setup (sda+sdb) where no encryption is present. But I have no idea what to do. Thanks!

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  • Poor performance of single processor 32bit Windows XP xompared SMP in VBA+Excel

    - by Adam Ryczkowski
    Welcome! On many computers I experienced poor performance of 32 bit guests running on 64 bit Linux host (I used only the Debian family). At last I managed to collect benchmark data. I made the benchmark by running custom VBA macro, (which we use in our company) that generates 284 pages long Word document full of Excel Pie charts, tables and comments. The macro is run as a single task (excluding the standard services) on a set of identically configured Windows XP 32-bit systems. I measured the time (in sec.) needed to perform the test. The computer (i.e. my notebook Asus P53E) supports both VT-d extensions and native Windows XP. It has 2-core processor, each core is hyperthreaded, so in total we have 4 mostly independent execution units. I use the latest VirtualBox 4.2 and VMWare Workstation 9.0 for Linux, installed together on the same host (running Mint 13 Maya) but never run simultaneously. The results (in column Time) are no less accurate than ± 10% Here are the results (sorry for the format, but I couldn't find out a better solution for tables in SO): +---------------+-------------+------------------------------------------------------+---------+------------+----------------+------+ | Host software | # processor | Windows kernel | IO APIC | VT-x/AMD-V | 2D Video Accel | Time | +---------------+-------------+------------------------------------------------------+---------+------------+----------------+------+ | VirtualBox | 1 | Advanced Configuration and Power Interface (ACPI) PC | 0 | 1 | 0 | 1139 | | VirtualBox | 1 | Advanced Configuration and Power Interface (ACPI) PC | 0 | 1 | 1 | 1050 | | VirtualBox | 1 | Advanced Configuration and Power Interface (ACPI) PC | 0 | 0 | 1 | 1644 | | VirtualBox | 4 | ACPI Multiprocessor PC | 1 | 1 | 1 | 6809 | | VMWare | 1 | ACPI Uniprocessor PC | | 1 | 1 | 1175 | | VMWare | 4 | ACPI Multiprocessor PC | | 1 | 1 | 3412 | | Native | 4 | ACPI Multiprocessor PC | | | | 1693 | | Native | 1 | Advanced Configuration and Power Interface (ACPI) PC | | | | 1170 | +---------------+-------------+------------------------------------------------------+---------+------------+----------------+------+ Here are the striking conclusions: Although I've read in the VirtualBox fora about abysmal performance with 32-bit guest on 64-bit host, VMWare also has problems compared to native run, still being twice faster(!) than VBox. Although VBA is inherently single-threaded, the Excel calculations, which take much more than a half of total computation time, supposedly aren't. So one would expect some speed gain when running on 2+ cores ("+" for hyperthreading). What we see is a speed loss. And quite big one too. For the VirtualBox the VT-d extension isn't a big deal. Can anyone shed some light on why the singlethreaded Windows kernel is so much faster than the SMP one?

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  • Wpf vs WinForms for a vb programmer? [closed]

    - by Jeroen
    I am asked by a client to develop an application that is basically a screen on which the user can choose several items to pass the time (used in holding cells in mental hospitals for example). The baisc idea is as follows: TV (choosing this will provide the user with a number of TV streams from the interweb) Radio (...) Games (serveral flash games, also from the interweb) Music (play local music or streams) Draw something (not the game) Create an email Choose lighting settings for the room etc. etc. I am torn between WinForms and WPF for this project. It seems that WPF is the way to go since there is quite a bit of rich media involved but I have a 15 year VB background. The project obviously has a dead line and certain budget that I cannot cross and if I can avoid starting from scratch with some thing that will be nice. Is WPF worth it in this particular case or can I use WinForms with the incorperation of WPF controls? I would very much like to hear your thoughts/comments/suggestions!

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  • Learning computer architecture as a programmer

    - by Samaursa
    I typically run across gurus at SO and other places (instructors, book authors etc.) that would say something along the lines "This will cause alignment issues" or other low level tidbits. I want to learn about all these tidbits that are relevant to programming. Now usually when I see low level books (computer architecture books for example) they are too low level and geared towards people whose primary area of interest is computer architecture and not software design. Do you have recommendations for books that go through low-level stuff that is relevant to programmers?

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  • how non-programmer become developer

    - by Sarang
    Every year there are different types of freshers getting recruited. But, our IT field is not only limited to IT Engineers & Computer Engineers. It is full of all different types of engineers. What is a way an engineer can be a proper developer ? I am asking this because, whatever engineering the student gone for, one can be shifted to IT development if he/she has some particular qualities within. What are those quelities required to be in a developer or required to be implemented to be developer ?

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  • Useful certifications for a young programmer

    - by Alain
    As @Paddyslacker elegantly stated in Are certifications worth it? The main purpose of certifications is to make money for the certifying body. I am a fairly young developer, with only an undergraduate degree, and my job is (graciously) offering to sponsor some professional development of my choice (provided it can be argued that it will contribute to the quality of work I do for them). A search online offers a slew of (mostly worthless) certifications one can attain. I'm wondering if there are any that are actually recognized in the (North American) industry as an asset. My local university promoted CIPS (I.S.P., ITCP) at the time I was graduating, but for all I can tell it's just the one that happened to get its foot in the door. It's certainly money grubbing - with a $205 a year fee. So are there any such certifications that provide useful credentials? To better define 'useful' - would it benefit full time developers, or is it only something worth while to the self-employed? Would any certifications lead me to being considered for higher wages, or can that only be achieved with more experience and an higher-level degree?

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  • C# books for the experienced programmer

    - by Michael Dmitry Azarkevich
    So I've been programming in C# for 3 years now (been programming in various languages for 3 years before that as well) and most of the stuff I learned I pieced together on the internet. The thing is, I want to understand C# more formally and in depth and so would like to get some books on the subjects. Any books you'd recommend? Also, I've heard good things about "C# 4.0 in a Nutshell", "Pro C# 2010 and the .NET 4 Platform" and "CLR via C#". What do you think of these? (The people at stackoverflow told me to take it here. Please, Please tell me I'm in the right place this time)

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  • Should Swing knowledge be required from Java programmers?

    - by Anto
    Swing is an integral part of the Java API. It is also the most popular GUI framework for Java. I still wonder, should every Java programmer still know, or at least be pretty familiar with, Swing (possibly excluding web developers)? There are alternatives (e.g. SWT), but they are not very widely used (compared to Swing). What do you think about requiring Swing knowledge from Java programmers? If such knowledge is important, to what degree? Are the basics enough or not? The reason I wonder is because I really don't like Swing but wonder if I still should brush up my skills in it. I'm able to create simple GUIs in it, but I would definitely not say that I know Swing well.

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  • When you are expecting a promoting, do you prefer an technical or administrative job? [closed]

    - by Darf Zon
    As a programmer, they offered me an upgrade as project manager, but my feeling is that I can have a more effective contribution in a technical role that in one administrative. When should I accept the promotion? Generally speaking, I think that people should do what they love and what they like to do, from the time you are offered a promotion to someone is because he has been doing a great job today, and certainly learn new things in the new position and obviously have a better financial remuneration, but if it really is something you do not like do not good that post. That's my opinion.

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