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My VPS provider gives me the choice between KVM and OpenVZ. What is the best choice for a VPS with 128MB or 256MB RAM?
KVM does not provide anywhere near the performance of OpenVZ (or Virtuozzo, its commercial equivalent). It's extremely important to note that KVM requires a running kernel inside the VPS, whereas OpenVZ runs containers using a shared kernel. This means that a 256MB KVM VPS does not actually have the same amount of memory available to userspace that OpenVZ does. OpenVZ is an extremely lightweight virtualization technology that easily outperforms full virtualization.
KVM does provide better isolation, although this isn't usually apparent to userspace in a container.
As for the original question, if I were shopping for a VPS, there are two factors to consider:
1) At the same price point, you'll get less for your money with KVM. 256MB of KVM is less than 256MB of OpenVZ because you have to run your own kernel so there's less for your actual applications. On the other hand, some hosters charge more for OpenVZ, so you'll need to do the math.
2) It's easier for hosting companies to overcommit OpenVZ systems, so bad hosting companies may put you on a system with too many containers, so be wary of this.
KVM has much better isolation than OpenVZ and in my experience KVM gets better performance as well. However I've heard some say they get better performance from OpenVZ. KVM has come a long way in the past year though, so I wouldn't be surprised if it's surpassed OpenVZ by now...
KVM also supports any operating system (in theory), whereas OpenVZ is limited to Linux only.
We're using KVM exclusively for our virtualization systems and have no interest in switching to anything else.
If your buying from a VPS provider, then KVM/Xen. OpenVZ/LXC suppliers can oversell their products.
If it's your own server then you can have a mix of OpenVZ/LXC and KVM on the same machine.
Choose KVM because OpenVZ is often cheaper to others hosts :)
OpenVZ does not give your processes the full amount of allocated memory due to overhead, so for smaller memory VPSes, I would lean towards choosing KVM or XEN.
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I recently had to enable VT for windows7 since I want to run ubuntu on vmware so I was wondering why isnt it enabled by default is it some kind of security issue or just not necessary for the average user?
There are several reasons, including "security" and "performance":
https://superuser.com/questions/291340/why-do-pc-manufacturers-disable-advanced-cpu-features-in-the-bios-by-default
http://www.vmware.com/pdf/asplos235_adams.pdf
Intel virtualization technology can get hardware intensive and although the software requirement is low (Windows Vista) only modern CPUs made by INTEL ONLY such as Intel i7 support it.
Not all windows computers have an Intel CPU though (a good amount of them do). The only people that use the VTX technology are developers and people who want to run a different operating system than their computer came with, so not everyone. As for security issue, I'm not sure but it can get very RAM intensive. (i.e. the Android HAXM for developers has a default RAM usage of 2GB, and the minimum is 512 MB!).
If you want to know more you can check out this article
or the website:
http://www.intel.com/content/www/us/en/virtualization/virtualization-technology/intel-virtualization-technology.html
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I have developed an app to analyze videos using OpenCV and Visual Studio 2013. I was planning to run this app in the Azure assuming that it will run faster in cloud. However, to my surprise, the app ran slower than my desktop, taking about twice the time when I configured the Azure instance with 8 cores. It is a 64-bit app, compiled with appropriate compiler optimization. Can someone help me understand why am I losing time in the cloud, and is there a way to improve the timing there?
The app takes as input a video (locally in each case) and outputs a flat file with the analysis data.
I am not sure why people are voting to close this question. This is very much about programming and if possible, please help me in pinpointing the problem.
There is only going to be 3 reasons for this
Disk IO speed
CPU Speed
Memory Speed
Taking a look here you can see someone who actually checked the performance of on premise to cloud: Azure compute power: Extra Large VM slow
Basically the Ghz is most likely slower (around 1.6) and disk IO speed, while local, is normally capped at 300 or 500 IOPS, which is only just higher than 15k rpm drives and no where near SSD level.
I am not sure on memory speed. While you can keep adding cores, most programs, even ones optimized for multiple cores, have a lot of dependencies on single threads, hence slowing the whole operation down. Increased Ghz is what can make a large difference.
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What would be optimal machine configuration(CPU power, memory, and drive technology) for following usage:
Visual studio 2010 and Visual studio 2012- several instances at once
Oracle navigator and MSSQL Management studio
+ some other programs (like GIMP, PDF converter, MS Office..)
The main goal is fast build and compile in Visual studio.
I have got to justify every component since it is config
for development machine at work.
There are some threads on Stackoverflow about that like:
SSD idea
I have not tried yet SSD proposal...
-OS Windows 8, 64bit
a multi-core architecture (with or without HyperThreading) will give you a performance gain when concurrently running clock cycle intensive operations, as each core has dedicated execution units and pipelining, so more cores equals less chance of applications having to timeshare e.g. while compiling.
A system with a lot of RAM will have advantages when switching between different instances of e.g. Visual Studio because their state won't need to be written away to (slower than RAM) disk, be it SSD or not.
It will also reduce disk I/O when working with Gimp, Photoshop or the likes.
The amount of cache can also have a positive influence on your daily work, because more (faster than RAM) cache will reduce the need for your system to leave the confines of the CPU and go the extra mile to read from/write to RAM.
Finally, the advantages of an SSD over "conventional" disks are mainly noticeable in disk and file access times. Booting the OS will be smoother, so will starting up programs from said SSD be. But SSD size is still fairly limited within a reasonable price range. Is it worth it? Imo, no. Once your tools have been loaded, there's little to no real need in a developer's day for SSD drives.
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I just purchased myself a IBM System x3650 and was wondering what the best way to set it up is. I'm going to be running 5 Drupal (php) websites from it. I have read numerous articles on virtualization and was wondering how I would go about doing this. Is virtualization better on a Windows machine VS Linux? Can I use Oracle VirtualBox. Any kind of help would be greatly appreciated!
If you're just going to run a bunch of websites, you don't need virtualization.
Virtualization takes your physical hardware and allows you to logically allocate it to virtual machines. You would install a hypervisor (such as Hyper-V or VMware ESX) rather than an Operating System. Then, you could create virtual machines and install Operating Systems on those (you can install any OS that the hypervisor support). Most hypervisors support Windows and Linux.
However to run 5 websites, use a web server that allows you to run multiple web sites on a single server. Both apache (httpd) and IIS (Windows Web Server) allow this. Virtualization would be overkill to accomplish this task.
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In this slide deck on Xen vs KVM, the benchmarks indicate that CPU and disk is nearly as fast under virtualization (~10% slowdown). Yet virtualization slows down a kernel compile by more than a factor of 2. What causes this?
A Linux kernel compile is a process heavy operation (lots of short-lived processes). Process creation/destruction involves setting up and tearing down MMU state. MMU virtualization is expensive (especially in software). There is a VMware whitepaper that shows the improvement in compile-time benchmarks when hardware MMU virtualization is used. I don't think the hardware used in the referenced slide provides hardware MMU virtualization. I don't know if either KVM or Xen support it (but I suspect so).