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  • Recommended storage scheme for home server? (LVM/JBOD/RAID 5...)

    - by j-g-faustus
    Are there any guidelines for which storage scheme(s) makes most sense for a multiple-disk home server? I am assuming a separate boot/OS disk (so bootability is not a concern, this is for data storage only) and 4-6 storage disks of 1-2 TB each, for a total storage capacity in the range 4-12 TB. The file system is ext4, I expect there will be only one big partition spanning all disks. As far as I can tell, the alternatives are individual disks pros: works with any combination of disk sizes; losing a disk loses only the data on that disk; no need for volume management. cons: data management is clumsy when logical units (like a "movies" folder) are larger than the capacity of any single drive. JBOD span pros: can merge disks of any size. cons: losing a disk loses all data on all disks LVM pros: can merge disks of any size; relatively simple to add and remove disks. cons: losing a disk loses all data on all disks RAID 0 pros: speed cons: losing one drive loses all data; disks must be same size RAID 5 pros: data survives losing one disk cons: gives up one disk worth of capacity; disks must be same size RAID 6 pros: data survives losing two disks cons: gives up two disks worth of capacity; disks must be same size I'm primarily considering either LVM or JBOD span simply because it will let me reuse older, smaller-capacity disks when I upgrade the system. The runner-up is RAID 0 for speed. I'm planning on having full backups to a separate system, so I expect the extra redundancy from RAID levels 5 or 6 won't be important. Is this a fair representation of the alternatives? Are there other considerations or alternatives I have missed? And what would you recommend?

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  • Linux fsck.ext3 says "Device or resource busy" although I did not mount the disk.

    - by matnagel
    I am running an ubuntu 8.04 server instance with a 8GB virtual disk on vmware 1.0.9. For disk maintenance I made a copy of the virtual disk (by making a copy of the 2 vmdk files of sda on the stopped vm on the host) and added it to the original vm. Now this vm has it's original virtual disk sda plus a 1:1 copy (sdd). There are 2 additional disk sdb and sdc which I ignore.) I would expect sdb not to be mounted when I start the vm. So I try tp do a ext2 fsck on sdd from the running vm, but it reports fsck reported that sdb was mounted. $ sudo fsck.ext3 -b 8193 /dev/sdd e2fsck 1.40.8 (13-Mar-2008) fsck.ext3: Device or resource busy while trying to open /dev/sdd Filesystem mounted or opened exclusively by another program? The "mount" command does not tell me sdd is mounted: $ sudo mount /dev/sda1 on / type ext3 (rw,relatime,errors=remount-ro) proc on /proc type proc (rw,noexec,nosuid,nodev) /sys on /sys type sysfs (rw,noexec,nosuid,nodev) varrun on /var/run type tmpfs (rw,noexec,nosuid,nodev,mode=0755) varlock on /var/lock type tmpfs (rw,noexec,nosuid,nodev,mode=1777) udev on /dev type tmpfs (rw,mode=0755) devshm on /dev/shm type tmpfs (rw) devpts on /dev/pts type devpts (rw,gid=5,mode=620) /dev/sdc1 on /mnt/r1 type ext3 (rw,relatime,errors=remount-ro) /dev/sdb1 on /mnt/k1 type ext3 (rw,relatime,errors=remount-ro) securityfs on /sys/kernel/security type securityfs (rw) When I ignore the warning and continue the fsck, it reported many errors. How do I get this under control? Is there a better way to figure out if sdd is mounted? Or how is it "busy? How to unmount it then? How to prevent ubuntu from automatically mounting. Or is there something else I am missing? Also from /var/log/syslog I cannot see it is mounted, this is the last part of the startup sequence: kernel: [ 14.229494] ACPI: Power Button (FF) [PWRF] kernel: [ 14.230326] ACPI: AC Adapter [ACAD] (on-line) kernel: [ 14.460136] input: PC Speaker as /devices/platform/pcspkr/input/input3 kernel: [ 14.639366] udev: renamed network interface eth0 to eth1 kernel: [ 14.670187] eth1: link up kernel: [ 16.329607] input: ImPS/2 Generic Wheel Mouse as /devices/platform/i8042/serio1/ kernel: [ 16.367540] parport_pc 00:08: reported by Plug and Play ACPI kernel: [ 16.367670] parport0: PC-style at 0x378, irq 7 [PCSPP,TRISTATE] kernel: [ 19.425637] NET: Registered protocol family 10 kernel: [ 19.437550] lo: Disabled Privacy Extensions kernel: [ 24.328857] loop: module loaded kernel: [ 24.449293] lp0: using parport0 (interrupt-driven). kernel: [ 26.075499] EXT3 FS on sda1, internal journal kernel: [ 28.380299] kjournald starting. Commit interval 5 seconds kernel: [ 28.381706] EXT3 FS on sdc1, internal journal kernel: [ 28.381747] EXT3-fs: mounted filesystem with ordered data mode. kernel: [ 28.444867] kjournald starting. Commit interval 5 seconds kernel: [ 28.445436] EXT3 FS on sdb1, internal journal kernel: [ 28.445444] EXT3-fs: mounted filesystem with ordered data mode. kernel: [ 31.309766] eth1: no IPv6 routers present kernel: [ 35.054268] ip_tables: (C) 2000-2006 Netfilter Core Team mysqld_safe[4367]: started mysqld[4370]: 100124 14:40:21 InnoDB: Started; log sequence number 0 10130914 mysqld[4370]: 100124 14:40:21 [Note] /usr/sbin/mysqld: ready for connections. mysqld[4370]: Version: '5.0.51a-3ubuntu5.4' socket: '/var/run/mysqld/mysqld.sock' port: 3 /etc/mysql/debian-start[4417]: Upgrading MySQL tables if necessary. /etc/mysql/debian-start[4422]: Looking for 'mysql' in: /usr/bin/mysql /etc/mysql/debian-start[4422]: Looking for 'mysqlcheck' in: /usr/bin/mysqlcheck /etc/mysql/debian-start[4422]: This installation of MySQL is already upgraded to 5.0.51a, u /etc/mysql/debian-start[4436]: Checking for insecure root accounts. /etc/mysql/debian-start[4444]: Checking for crashed MySQL tables.

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  • Why Doesn’t Disk Cleanup Delete Everything from the Temp Folder?

    - by The Geek
    After you’ve used Disk Cleanup, you probably expect every temporary file to be completely deleted, but that’s not actually the case. Files are only deleted if they are older than 7 days old, but you can tweak that number to something else. This is one of those tutorials that we’re showing you for the purpose of explaining how something works, but we’re not necessarily recommending that you implement it unless you really understand what’s going on. Keep reading for more Latest Features How-To Geek ETC The How-To Geek Guide to Learning Photoshop, Part 8: Filters Get the Complete Android Guide eBook for Only 99 Cents [Update: Expired] Improve Digital Photography by Calibrating Your Monitor The How-To Geek Guide to Learning Photoshop, Part 7: Design and Typography How to Choose What to Back Up on Your Linux Home Server How To Harmonize Your Dual-Boot Setup for Windows and Ubuntu Hang in There Scrat! – Ice Age Wallpaper How Do You Know When You’ve Passed Geek and Headed to Nerd? On The Tip – A Lamborghini Theme for Chrome and Iron What if Wile E. Coyote and the Road Runner were Human? [Video] Peaceful Winter Cabin Wallpaper Store Tabs for Later Viewing in Opera with Tab Vault

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  • VirtualBox guest OS accessing local server on host OS.

    - by Maxim
    Hi, On my Ubuntu HOST I have my local webserver. I installed VirtualBox and Debian as a GUEST. I would like Debian guest to be able to hit my webserver running on my Ubuntu host (for example, I just type http://localhost:8080/ in the browser under Debian). How can this be done? Thanks in advance.

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  • How to find out memory layout of your data structure implementation on Linux 64bit machine

    - by ajay
    In this article, http://cacm.acm.org/magazines/2010/7/95061-youre-doing-it-wrong/fulltext the author talks about the memory layouts of 2 data structures - The Binary Heap and the B-Heap and compares how one has better memory layout than the other. http://deliveryimages.acm.org/10.1145/1790000/1785434/figs/f5.jpg http://deliveryimages.acm.org/10.1145/1790000/1785434/figs/f6.jpg I want to get hands on experience on this. I have an implementation of a N-Ary Tree and I want to find out the memory layout of my data structure. What is the best way to come up with a memory layout like the one in the article? Secondly, I think it is easier to identify the memory layout if it is an array based implementation. If the implementation of a Tree uses pointers then what Tools do we have or what kind of approach is required to map it's memory layout? Thanks!

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  • Linux: page faults and network filesystems

    - by Alex B
    If a Linux system runs out of physical memory, does it drop inactive executable code pages? I assume the answer is yes, since there is no reason to keep them in swap, so they are simply discarded and re-loaded if necessary (as far as I know, that's what FreeBSD does). If the above is true for Linux, my question is, how does it handle executables run from network filesystems (e.g. NFS)? Does it go and fetch executable pages over the network if there is a page fault?

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  • How do you limit root partition disk access to allow drive to go into stanby mode?

    - by Casey
    When there are no users on my system, I would like the hard disk to spindown to low-power state. I realize that this might not be 100% achievable for a straight 24 hours, but it seems reasonable that the system could remain idle for a few hours at a time when it is not in use. My system is headless and running a limited number of services. The primary services are: exim4, mythtv-backend, nfs, samba, cups, apt-cacher-ng Assume that drives are already enabled to go into standby mode. Also, its not acceptable to increase the write-back timeout, since my system is not on a UPS.

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  • Why does Java's invokevirtual need to resolve the called method's compile-time class?

    - by Chris
    Consider this simple Java class: class MyClass { public void bar(MyClass c) { c.foo(); } } I want to discuss what happens on the line c.foo(). At the bytecode level, the meat of c.foo() will be the invokevirtual opcode, and, according to the documentation for invokevirtual, more or less the following will happen: Look up the foo method defined in compile-time class MyClass. (This involves first resolving MyClass.) Do some checks, including: Verify that c is not an initialization method, and verify that calling MyClass.foo wouldn't violate any protected modifiers. Figure out which method to actually call. In particular, look up c's runtime type. If that type has foo(), call that method and return. If not, look up c's runtime type's superclass; if that type has foo, call that method and return. If not, look up c's runtime type's superclass's superclass; if that type has foo, call that method and return. Etc.. If no suitable method can be found, then error. Step #3 alone seems adequate for figuring out which method to call and verifying that said method has the correct argument/return types. So my question is why step #1 gets performed in the first place. Possible answers seem to be: You don't have enough information to perform step #3 until step #1 is complete. (This seems implausible at first glance, so please explain.) The linking or access modifier checks done in #1 and #2 are essential to prevent certain bad things from happening, and those checks must be performed based on the compile-time type, rather than the run-time type hierarchy. (Please explain.)

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  • What can I do to give some more love and disk space to my database on Ubuntu?

    - by Yaron Naveh
    I'm new to linux. I've deployed a db to ubuntu server on amazon and found out I'm low on disk space. did df (see below) - and found out that I'm 89% capacity on one file system, but less on others. What does this mean? Do I have a few partitions and can now utilize others besides /dev/xvda1? Also /dev/xvdb seems large, is it safe to put the db in it and only use it? If so do I need to mount it or do something special? $> df -lah Filesystem Size Used Avail Use% Mounted on /dev/xvda1 8.0G 6.7G 914M 89% / proc 0 0 0 - /proc sysfs 0 0 0 - /sys none 0 0 0 - /sys/fs/fuse/connections none 0 0 0 - /sys/kernel/debug none 0 0 0 - /sys/kernel/security udev 3.7G 8.0K 3.7G 1% /dev devpts 0 0 0 - /dev/pts tmpfs 1.5G 164K 1.5G 1% /run none 5.0M 0 5.0M 0% /run/lock none 3.7G 0 3.7G 0% /run/shm /dev/xvdb 414G 199M 393G 1% /mnt

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  • VS2010 Developer Image

    - by David Ward
    I am about to create a new developer PC image for developing WPF applications using VS2010, WCF, SQL2008 and SharePoint2010. What OS should I opt for? Windows 7? Windows Server 2008 R2? I'd have thought Windows 7 to make sure that I have a similar experience during development as an end user, however I can't install SharePoint on a client OS and so thought about Windows Server 2008 R2 to help with the SharePoint development process. Thoughts?

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  • Can you force a crash if a write occurs to a given memory location with finer than page granularity?

    - by Joseph Garvin
    I'm writing a program that for performance reasons uses shared memory (alternatives have been evaluated, and they are not fast enough for my task, so suggestions to not use it will be downvoted). In the shared memory region I am writing many structs of a fixed size. There is one program responsible for writing the structs into shared memory, and many clients that read from it. However, there is one member of each struct that clients need to write to (a reference count, which they will update atomically). All of the other members should be read only to the clients. Because clients need to change that one member, they can't map the shared memory region as read only. But they shouldn't be tinkering with the other members either, and since these programs are written in C++, memory corruption is possible. Ideally, it should be as difficult as possible for one client to crash another. I'm only worried about buggy clients, not malicious ones, so imperfect solutions are allowed. I can try to stop clients from overwriting by declaring the members in the header they use as const, but that won't prevent memory corruption (buffer overflows, bad casts, etc.) from overwriting. I can insert canaries, but then I have to constantly pay the cost of checking them. Instead of storing the reference count member directly, I could store a pointer to the actual data in a separate mapped write only page, while keeping the structs in read only mapped pages. This will work, the OS will force my application to crash if I try to write to the pointed to data, but indirect storage can be undesirable when trying to write lock free algorithms, because needing to follow another level of indirection can change whether something can be done atomically. Is there any way to mark smaller areas of memory such that writing them will cause your app to blow up? Some platforms have hardware watchpoints, and maybe I could activate one of those with inline assembly, but I'd be limited to only 4 at a time on 32-bit x86 and each one could only cover part of the struct because they're limited to 4 bytes. It'd also make my program painful to debug ;)

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  • How does memory protection in SASOS works?

    - by chris
    I'd like to know how it works - whether it checks if process can read/write/execute memory on every access, or it does it only once? But when it does it only once, and all processes are in a single address space, how are these other hostile processes are prevented from accessing memory from not their's areas?

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  • How to create a container that holds different types of function pointers in C++?

    - by Alex
    I'm doing a linear genetic programming project, where programs are bred and evolved by means of natural evolution mechanisms. Their "DNA" is basically a container (I've used arrays and vectors successfully) which contain function pointers to a set of functions available. Now, for simple problems, such as mathematical problems, I could use one type-defined function pointer which could point to functions that all return a double and all take as parameters two doubles. Unfortunately this is not very practical. I need to be able to have a container which can have different sorts of function pointers, say a function pointer to a function which takes no arguments, or a function which takes one argument, or a function which returns something, etc (you get the idea)... Is there any way to do this using any kind of container ? Could I do that using a container which contains polymorphic classes, which in their turn have various kinds of function pointers? I hope someone can direct me towards a solution because redesigning everything I've done so far is going to be painful.

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  • Oracle makes Virtualized Java Applications Practical. Announces Brand New Products

    - by blake.connell
    New Oracle Virtual Assembly Builder and Oracle WebLogic Suite Virtualization Option make running Java applications in a virtual environments easy and practical. • Oracle Virtual Assembly Builder is a new product designed to help organizations quickly and easily deploy multi-tier enterprise applications in virtualized environments. It enables administrators to quickly configure and provision these applications. • Oracle WebLogic Suite Virtualization Option delivers Oracle WebLogic Server on Oracle JRockit Virtual Edition delivering 'near-native' performance and increased server density. • Oracle WebLogic Server on Oracle JRockit Virtual Edition runs directly on Oracle VM without a guest operating system, a unique capability resulting in better performance and more application server runtime per system. Oracle WebLogic Suite Virtualization Option and Oracle Virtual Assembly Builder can drive operational efficiency and agility. Customers can dynamically scale up/down the underlying software infrastructure and applications with ease through software automation. Register for a live webinar with Oracle product experts Read the press release For more product information: Oracle Virtual Assembly Builder Oracle WebLogic Suite Virtualization Option

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  • Disk2vhd Hyper-V server question

    - by user297378
    Hello all I have a backed up about 30 servers using disk2vhd and now I have built my first of many hyper-v severs I did not realize this is all command line I did download CoreConfigurator and that does have some functionality I have been looking for. My question is how do I get the VHD files to run a Vitual Machines? its all command line I tried via vbs to mount the VHD's and I have not been able to any help on this would be great! Thanks!

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  • searching for a programming platform with hot code swap

    - by Andreas
    I'm currently brainstorming over the idea how to upgrade a program while it is running. (Not while debugging, a "production" system.) But one thing that is required for it, is to actually submit the changed source code or compiled byte code into the running process. Pseudo Code var method = typeof(MyClass).GetMethod("Method1"); var content = //get it from a database (bytecode or source code) SELECT content FROM methods WHERE id=? AND version=? method.SetContent(content); At first, I want to achieve the system to work without the complexity of object-orientation. That leads to the following requirements: change source code or byte code of function drop functions add new functions change the signature of a function With .NET (and others) I could inject a class via an IoC and could thus change the source code. But the loading would be cumbersome, because everything has to be in an Assembly or created via Emit. Maybe with Java this would be easier? The whole ClassLoader is replacable, I think. With JavaScript I could achieve many of the goals. Simply eval a new function (MyMethod_V25) and assign it to MyClass.prototype.MyMethod. I think one can also drop functions somehow with "del" Which general-purpose platform can handle such things?

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  • Self-describing file format for gigapixel images?

    - by Adam Goode
    In medical imaging, there appears to be two ways of storing huge gigapixel images: Use lots of JPEG images (either packed into files or individually) and cook up some bizarre index format to describe what goes where. Tack on some metadata in some other format. Use TIFF's tile and multi-image support to cleanly store the images as a single file, and provide downsampled versions for zooming speed. Then abuse various TIFF tags to store metadata in non-standard ways. Also, store tiles with overlapping boundaries that must be individually translated later. In both cases, the reader must understand the format well enough to understand how to draw things and read the metadata. Is there a better way to store these images? Is TIFF (or BigTIFF) still the right format for this? Does XMP solve the problem of metadata? The main issues are: Storing images in a way that allows for rapid random access (tiling) Storing downsampled images for rapid zooming (pyramid) Handling cases where tiles are overlapping or sparse (scanners often work by moving a camera over a slide in 2D and capturing only where there is something to image) Storing important metadata, including associated images like a slide's label and thumbnail Support for lossy storage What kind of (hopefully non-proprietary) formats do people use to store large aerial photographs or maps? These images have similar properties.

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  • memory available to 64bit Fedora guest under 32bit XP host running virtualbox

    - by Chris Card
    I have successfully installed a 64 bit Fedora 11 guest os using VirtualBox on a host machine (AMD64) running 32 bit Windows XP . At the moment the host machine has 2 Gb ram installed and I've allocated 1 Gb to the guest, which all works well. The host machine can hold a maximum of 4 Gb ram, so I was wondering if it's worth buying an extra 2 Gb for it. I know that 32 bit Windows XP can't use all of the 4 Gb, but can the guest os use any of the ram that the host os can't use?

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  • WITH_OBJECT_HEADERS enabled GC from Dalvik?

    - by Wonil
    Hello, As I know Dalvik VM does not support generational GC as default. But, I found "WITH_OBJECT_HEADERS" compilation flag which could be related with generational GC from HeapInternal.h file. typedef struct DvmHeapChunk { #if WITH_OBJECT_HEADERS u4 header; const Object *parent; const Object *parentOld; const Object *markFinger; const Object *markFingerOld; u2 birthGeneration; u2 markCount; u2 scanCount; u2 oldMarkGeneration; u2 markGeneration; u2 oldScanGeneration; u2 scanGeneration; #endif Does anyone try to build Dalvik with this option enabled? Do you know anything about generational GC support from Dalvik? Regards, Wonil.

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  • Identifying CDs

    - by Chris
    I'd like to be able to determine what music album CD is in a CD drive. For example, if someone claims that the CD in their drive is Eminem - The Eminem Show, I would like to be able to verify that the CD is indeed The Eminem Show. Any ideas? I've applied for a Gracenote developer license, but they won't get back to me for five days. Also, how does this work? Is there some GUID or other unique identifier that music discs are encoded with? Lastly, might this be possible with data CDs, like, say, the Diablo II install Disc 1? If so, any directions you can point me in, for accomplishing this?

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  • Understanding Virtualization

    - by mohit
    Hi, I wana to know about Virtualization in detail. But start from basics, like what is virtualization, with real world examples and scenarios. When ever i search, i got Virtualization technologies, but i want to learn and in fcat know what exactly is virtualization, its types n all..... Please help me in getting practical details of term "Virtualization"

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