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  • How can a single disk in a hardware SATA RAID-10 array bring the entire array to a screeching halt?

    - by Stu Thompson
    Prelude: I'm a code-monkey that's increasingly taken on SysAdmin duties for my small company. My code is our product, and increasingly we provide the same app as SaaS. About 18 months ago I moved our servers from a premium hosting centric vendor to a barebones rack pusher in a tier IV data center. (Literally across the street.) This ment doing much more ourselves--things like networking, storage and monitoring. As part the big move, to replace our leased direct attached storage from the hosting company, I built a 9TB two-node NAS based on SuperMicro chassises, 3ware RAID cards, Ubuntu 10.04, two dozen SATA disks, DRBD and . It's all lovingly documented in three blog posts: Building up & testing a new 9TB SATA RAID10 NFSv4 NAS: Part I, Part II and Part III. We also setup a Cacit monitoring system. Recently we've been adding more and more data points, like SMART values. I could not have done all this without the awesome boffins at ServerFault. It's been a fun and educational experience. My boss is happy (we saved bucket loads of $$$), our customers are happy (storage costs are down), I'm happy (fun, fun, fun). Until yesterday. Outage & Recovery: Some time after lunch we started getting reports of sluggish performance from our application, an on-demand streaming media CMS. About the same time our Cacti monitoring system sent a blizzard of emails. One of the more telling alerts was a graph of iostat await. Performance became so degraded that Pingdom began sending "server down" notifications. The overall load was moderate, there was not traffic spike. After logging onto the application servers, NFS clients of the NAS, I confirmed that just about everything was experiencing highly intermittent and insanely long IO wait times. And once I hopped onto the primary NAS node itself, the same delays were evident when trying to navigate the problem array's file system. Time to fail over, that went well. Within 20 minuts everything was confirmed to be back up and running perfectly. Post-Mortem: After any and all system failures I perform a post-mortem to determine the cause of the failure. First thing I did was ssh back into the box and start reviewing logs. It was offline, completely. Time for a trip to the data center. Hardware reset, backup an and running. In /var/syslog I found this scary looking entry: Nov 15 06:49:44 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_00], 6 Currently unreadable (pending) sectors Nov 15 06:49:44 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_07], SMART Prefailure Attribute: 1 Raw_Read_Error_Rate changed from 171 to 170 Nov 15 06:49:45 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_10], 16 Currently unreadable (pending) sectors Nov 15 06:49:45 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_10], 4 Offline uncorrectable sectors Nov 15 06:49:45 umbilo smartd[2827]: Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error Nov 15 06:49:45 umbilo smartd[2827]: # 1 Short offline Completed: read failure 90% 6576 3421766910 Nov 15 06:49:45 umbilo smartd[2827]: # 2 Short offline Completed: read failure 90% 6087 3421766910 Nov 15 06:49:45 umbilo smartd[2827]: # 3 Short offline Completed: read failure 10% 5901 656821791 Nov 15 06:49:45 umbilo smartd[2827]: # 4 Short offline Completed: read failure 90% 5818 651637856 Nov 15 06:49:45 umbilo smartd[2827]: So I went to check the Cacti graphs for the disks in the array. Here we see that, yes, disk 7 is slipping away just like syslog says it is. But we also see that disk 8's SMART Read Erros are fluctuating. There are no messages about disk 8 in syslog. More interesting is that the fluctuating values for disk 8 directly correlate to the high IO wait times! My interpretation is that: Disk 8 is experiencing an odd hardware fault that results in intermittent long operation times. Somehow this fault condition on the disk is locking up the entire array Maybe there is a more accurate or correct description, but the net result has been that the one disk is impacting the performance of the whole array. The Question(s) How can a single disk in a hardware SATA RAID-10 array bring the entire array to a screeching halt? Am I being naïve to think that the RAID card should have dealt with this? How can I prevent a single misbehaving disk from impacting the entire array? Am I missing something?

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  • "Wireless disabled by hardware switch" after suspend and other hardware buttons ineffective - how can I solve this?

    - by fahadayaz
    I have recently purchased a Novatech nFinity N1410 laptop and am having problems with the wireless, which sudo lshw -C network tells me is Centrino Wireless-N 2230 and using the iwlwifi driver. The problem is that after the device has been suspended, I am not able to get the wireless working again without a restart. The network indicator states that the wireless disabled by hardware switch. Though Fn+F2 is meant to be the wireless switch, xev tells me that the system doesn't see it as anything at all when I press this hardware combination. Also, though the brightness up/down buttons work fine, the volume up/down buttons do not work either. What can I do to fix this? I am running Ubuntu 12.10 with all available updates installed.

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  • Coherence on Exalogic: 6x Speeds on Half the Hardware is Possible

    - by jeckels
    Recently, Oracle Coherence released its 12c version, focused on scalability and real-time data delivery. As part of the launch, we showcased Coherence's tight coupling with Exalogic Elastic Cloud. By leveraging the Inifiniband Fabric in Exalogic, Coherence can now operate at up to 6x the speed on as little as half the hardware on an Exalogic box. This breakthrough is helping customers save money on their hardware costs while improving performance of their data grid. Here's a free resource available for you to explore this technology relationship further.For even more information on Coherence, attend our upcoming free virtual developer day on November 5th to see how developers can leverage Coherence in their everyday tasks.

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  • How long to install a new RAID 1 pair in linux using hardware RAID?

    - by Roger H
    Hi, I need to install a pair of 1Tb disks into a server that has a hardware RAID card. How long is it likely to take to configure the RAID controller - sticking the disks in is only a 5 minute job, but is there likely to be significant downtime while both disks mirror (even though they are both blank)? Am I looking at 10 minutes over all, or more like 2 hours for this to happen? Thanks

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  • No "Safely Remove Hardware" for USB-Connected External Hard Disk? (Windows XP)

    - by deathlock
    I have several external hard disks with different brands. Each time I connect those hard disk to my laptop (with USB), there is no option for Safely Remove Hardware / Eject. This problem only seem to occur with external hard disks, since the option is there if I connect with USB Flash Drives. Why is it happening and is there any way to enable it? What is the best method to remove an external hard disk?

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  • what is the a good hardware for a small business server? [closed]

    - by mans
    I need to setup a server for our small team. I neeed to install: 1- a version control application 2- Continus built application (the application needs to be built on windows) 3- WIKI 4- project managment software 5- issue tracking software 6- file sharing I think I need a raid 1 server for mirroring. Since it is not a database server, I am not interestred in raid 0. What is a suitable hardware for this server and where can I buy it in UK?

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  • How does object of sub-class record information about its super-class the in a Virtual Inheritance

    - by Summer_More_More_Tea
    Hi there: I encounter this problem when tackling with virtual inheritance. I remember that in a non-virtual inheritance hierarchy, object of sub-class hold an object of its direct super-class. What about virtual inheritance? In this situation, does object of sub-class hold an object of its super-class directly or just hold a pointer pointing to an object of its super-class? By the way, why the output of the following code is: sizeof(A): 8 sizeof(B): 20 sizeof(C): 32 Code: #include <iostream> using namespace std; class A{ char k[ 3 ]; public: virtual void a(){}; }; class B : public virtual A{ char j[ 3 ]; public: virtual void b(){}; }; class C : public virtual B{ char i[ 3 ]; public: virtual void c(){}; }; int main( int argc, char *argv[] ){ cout << "sizeof(A): " << sizeof( A ) << endl; cout << "sizeof(B): " << sizeof( B ) << endl; cout << "sizeof(C): " << sizeof( C ) << endl; return 0; } Thanks in advance. Kind regards.

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  • Non Blocking Keyboard on WinCE accessing the virtual keyboard

    - by Jan H.
    Hello Guys, I am desperately looking for a solution that enables me to read keyboard events in a non blocking way. These Keyboard events are generated by a VIRTUAL KEYBOARD that comes with the WinCE device. I have a console application running in C++, where the user is asked to navigate via 'ESC', 'U' and other characters through the menu. I first tried to use fread and stdin and realised that it is blocking call and waits for a carriage return. Then I tried to hook up to the windows message WM_KEYUP, but I never recieve this windows message. Furthermore I tried to use QtGUI together with the event QKeyEvent, but I never recieve any event. I wonder if it is in general possible to recieve non-blocking keyboard events on a WinCE device. I would be glad if you have any suggestions! Cheers, Jan

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  • vir-install virtual machine hang on Probbing EDD

    - by user2256235
    I'm using vir-stall virtual machine, and my command is virt-install --name=gust --vcpus=4 --ram=8192 --network bridge:br0 --cdrom=/opt/rhel-server-6.2-x86_64-dvd.iso --disk path=/opt/as1/as1.img,size=50 --accelerate After running the command, it hangs on probing EDD, - Press the <ENTER> key to begin the installation process. +----------------------------------------------------------+ | Welcome to Red Hat Enterprise Linux 6.2! | |----------------------------------------------------------| | Install or upgrade an existing system | | Install system with basic video driver | | Rescue installed system | | Boot from local drive | | Memory test | | | | | | | | | | | | | | | +----------------------------------------------------------+ Press [Tab] to edit options Automatic boot in 57 seconds... Loading vmlinuz...... Loading initrd.img...............................ready. Probing EDD (edd=off to disable)... ok ÿ Previously, I wait a long time, it seems no marching. After I press ctrl + ] and stop it. I find it was running using virsh list, but I cannot console it using virsh concole gust. Any problem and how should I do. Many Thanks

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  • Access virtualhosts over LAN (Also in xpmode (Virtual PC))

    - by Pheter
    Hi, I am running Wamp on my computer (the host). I have set up several virtualhosts in apache and they are working fine when I access them from the same computer (host). I have installed Windows XPMode on my computer (which is running windows 7). XPMode (which uses Virtual PC) is set up to use a NAT network. The network in XPMode is working fine, and I can access the host PC via the IP address 192.168.1.5, just as I would if I was using any physical computer on the same network. I can view all the web pages at 192.168.1.5 and it's subdirectories. However, I cannot access any of the subdomains that are configured in the virtualhosts of the host computer. How can I access the subdomains? I don't think that the fact that I am using XPMode and am using a virtualized OS has anything to do with it, but I thought that it was worth mentioning.

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  • ASP.Net Application Trust Medium File IO Outside Virtual Directory

    - by Trey Gramann
    I am trying to determine how suicidal this is... I have a hosting environment where a custom ASP.Net CMS application needs to access the files in the root folder of a website even though it is in a virtual folder so it can be shared accross many sites. I can modify the Medium trust on the server and came up with this... <IPermission class="FileIOPermission" version="1" Read="$AppDir$;$AppDir$\.." Write="$AppDir$;$AppDir$\.." Append="$AppDir$;$AppDir$\.." PathDiscovery="$AppDir$;$AppDir$\.."/> Oddly enough, it works. Yes, I understand it is doing this for all the Apps. I am a bit at a loss as to easy ways to test what else is being exposed. Feels dangerous. Opinions?

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  • virtual function call from base of base

    - by th3g0dr3d
    hi, let's say i have something like this (very simplified): <pre><code> class base { void invoke() { this-foo(); } virtual void foo() = 0; }; class FirstDerived : public base { void foo() { // do stuff } }; class SecondDerived : public FirstDerived { // other not related stuff } int main() { SecondDerived *a = new SecondDerived(); a-invoke(); } What i see in the debugger is that base::invoke() is called and tries to call this-foo(); (i expect FirstDerived::foo() to be called), the debugger takes me to some unfamiliar assembly code (probably because it jumped to unrelated areas) and after few lines i get segmentation fault. am i doing something wrong here? :/ thanks in advance

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  • How do i translate movement on the Canvas3D to movement in the virtual 3D world

    - by Coder
    My goal is to move a shape in the virtual world in such a way so that it ends up where the mouse pointer is on the canvas. What i have: -mouse position (x,y) on a Canvas3D object -Point3d object of where a pick ray starting from the Canvas3D viewport intersects with the first scene object. (point in 3D space of where i want to start the drag) What i want: -Some way to translate the Point3d's coordinates so that the initial point of intersection (the Point3d object) is always overlapping the the mouse position on the canvas (same as when i used the pick ray to determine what the user clicked on from the Canvas3D object). Thanks!

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  • Tuning OS X Virtual Memory

    - by dcolish
    I've noticed some really odd results form vm_stat on OSX 10.6. According to this, its barely hitting the cache. Searches of pretty much everywhere I could think of turn up little to explain why the rate is so low. I asked a few friends and they're seeing the same thing. What gives and how can I make it better? Mach Virtual Memory Statistics: (page size of 4096 bytes) Pages free: 78609. Pages active: 553411. Pages inactive: 191116. Pages speculative: 6198. Pages wired down: 153998. "Translation faults": 116031508. Pages copy-on-write: 2274338. Pages zero filled: 33360804. Pages reactivated: 264378. Pageins: 1197683. Pageouts: 43756. Object cache: 20 hits of 1550639 lookups (0% hit rate)

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  • How does a virtual machine work?

    - by Martin
    I've been looking into how programming languages work, and some of them have a so-called virtual machines. I understand that this is some form of emulation of the programming language within another programming language, and that it works like how a compiled language would be executed, with a stack. Did I get that right? With the proviso that I did, what bamboozles me is that many non-compiled languages allow variables with "liberal" type systems. In Python for example, I can write this: x = "Hello world!" x = 2**1000 Strings and big integers are completely unrelated and occupy different amounts of space in memory, so how can this code even be represented in a stack-based environment? What exactly happens here? Is x pointed to a new place on the stack and the old string data left unreferenced? Do these languages not use a stack? If not, how do they represent variables internally?

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  • Override number of parameters of pure virtual functions

    - by Jir
    I have implemented the following interface: template <typename T> class Variable { public: Variable (T v) : m_value (v) {} virtual void Callback () = 0; private: T m_value; }; A proper derived class would be defined like this: class Derived : public Variable<int> { public: Derived (int v) : Variable<int> (v) {} void Callback () {} }; However, I would like to derive classes where Callback accepts different parameters (eg: void Callback (int a, int b)). Is there a way to do it?

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  • iOS 5 fixed positioning and virtual keyboard

    - by jeffc
    I have a mobile website which has a div pinned to the bottom of the screen via position:fixed. All works fine in iOS 5 (I'm testing on an iPod Touch) until I'm on a page with a form. When I tap into an input field and the virtual keyboard appears, suddenly the fixed position of my div is lost. The div now scrolls with the page as long as the keyboard is visible. Once I click Done to close the keyboard, the div reverts to its position at the bottom of the screen and obeys the position:fixed rule. Has anyone else experienced this sort of behavior? Is this expected? Thanks.

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  • How many layers are between my program and the hardware?

    - by sub
    I somehow have the feeling that modern systems, including runtime libraries, this exception handler and that built-in debugger build up more and more layers between my (C++) programs and the CPU/rest of the hardware. I'm thinking of something like this: 1 + 2 OS top layer Runtime library/helper/error handler a hell lot of DLL modules OS kernel layer Do you really want to run 1 + 2?-Windows popup (don't take this serious) OS kernel layer Hardware abstraction Hardware Go through at least 100 miles of circuits Eventually arrive at the CPU ADD 1, 2 Go all the way back to my program Nearly all technical things are simply wrong and in some random order, but you get my point right? How much longer/shorter is this chain when I run a C++ program that calculates 1 + 2 at runtime on Windows? How about when I do this in an interpreter? (Python|Ruby|PHP) Is this chain really as dramatic in reality? Does Windows really try "not to stand in the way"? e.g.: Direct connection my binary < hardware?

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  • NTFS-compressing Virtual PC disks (on host and/or guest)

    - by nlawalker
    I'm hoping someone here can answer these definitively: Does putting a VHD file in an NTFS-compressed folder on the host improve performance of the virtual machine, diminish performance, or neither? What about using NTFS compression within the guest? Does using compresssion on either the host or the guest lead to any problems like read or write errors? If I were to put a VHD in a compressed folder on the host, would I benefit from compacting it? I've seen references to using NTFS compression on quite a few VPC "tips and tricks" blog posts, and it seems like half of them say to never do it and the other half say that not only does it save disk space but it actually can improve performance if you have a fast CPU and your primary performance bottleneck is the disk.

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