Virtualization is a group of software technologies that allow abstraction between layers of a system. This allows separation between the logical layers of the system, providing isolation, flexibility, and/or the ability to run more than one at a time. This differs from most traditional systems where ...

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4answers
12k views

Why is TCP accept() performance so bad under Xen?

The rate at which my server can accept() new incoming TCP connections is really bad under Xen. The same test on bare metal hardware shows 3-5x speed ups. How come this is so bad under Xen? Can you ...
54
votes
7answers
5k views

What are the drawbacks of running a database inside a virtual machine? How do I overcome them? [closed]

Running anything inside a virtual machine will have some level of performance hit, but how much does it really impact the performance of a database system? I found this academic reference paper with ...
45
votes
9answers
91k views

Creating a virtual machine in VirtualBox from a physical one

Is there any way to create a virtual machine that you can use in VirtualBox from a physical installation that you have? For instance, if I have Windows XP installed on a physical computer and want to ...
40
votes
2answers
2k views

vSphere education - What are the downsides of configuring VMs with *too* much RAM?

VMware memory management seems to be a tricky balancing act. With cluster RAM, Resource Pools, VMware's management techniques (TPS, ballooning, host swapping), in-guest RAM utilization, swapping, ...
39
votes
2answers
2k views

Why do systems generally disable virtualization by default in BIOS settings?

I have yet to see a system whose default configuration enables MMU and directed I/O virtualization. Often this necessitates rebooting and going into the BIOS to enable it if you want, e.g., 64-bit ...
35
votes
9answers
35k views

Virtualization for Linux (VMware vs VirtualBox vs KVM vs …)? [closed]

I'm trying to decide on which of these to use. The ones I know about are: VMware (various flavours); VirtualBox; KVM. Now ideally I'd like the following features: Ideally to be able to boot a ...
33
votes
7answers
18k views

Replace VMware vSphere infrastructure with open source alternatives?

We are planning a slow migration from VMware (and third party apps) to open source alternatives (free would be great). Basically, we want to start with some little cluster lab, then migrate the ...
31
votes
5answers
5k views

Are VMware ESXi 5 patches cumulative?

This seems basic, but I'm confused about the patching strategy involved with manually updating standalone VMware ESXi hosts. The VMware vSphere blog attempts to explain this, but the actual process is ...
27
votes
5answers
22k views

What range of MAC addresses can I safely use for my virtual machines?

I want to assign my virtual machines MAC addresses so that I can configure DHCP reservations for them so that they always get the same IP address regardless of which host hypervisor they are running ...
27
votes
11answers
20k views

Is virtual machine slower than the underlying physical machine?

This question is quite general, but most specifically I'm interested in knowing if virtual machine running Ubuntu Enterprise Cloud will be any slower than the same physical machine without any ...
26
votes
11answers
2k views

When deploying a single server on new hardware, do you virtualize it or not?

There are a few questions that I've found on ServerFault that hint around this topic, and while it may be somewhat opinion-based, I think it can fall into that "good subjective" category based on the ...
26
votes
2answers
38k views

Difference between Xen PV, Xen KVM and HVM?

I know that Xen is usually better than OpenVZ as the provider cannot oversell in Xen. However, what is the difference between Xen PV, Xen KVM and HVM (I was going through this provider's specs? Which ...
25
votes
4answers
714 views

Will virtualizing a server mean another OS layer to patch and update, more work and greater risk?

I've done a search and have not found anything addressing issues regarding patching and system updates. I've got guidelines that say servers need to have necessary patches. If I have a VM host then ...
20
votes
17answers
2k views

Virtualization Pitfalls/Lessons Learned

What are some pitfalls or lessons learned after converting existing hardware to a virtualized environment? Is there anything you tried to virtualize but will never do again?
20
votes
6answers
6k views

Can windows domain controller be virtualized?

Just the question on the title. There is any problem? Any experience on this?
19
votes
6answers
1k views

Can a VMWare Server 2.0 virtual machine be “unvirtualized” to physical hardware?

We have a number of VMWare Server 2.0 virtual machines that were created using VMWare Converter (It copies a physical machine to a virtual machine). If we need to convert the virtual machine back to a ...
18
votes
1answer
10k views

Vagrant set default share permissions

When running a vagrant instance the project folder is mounted on /vagrant automatically. However is mounted with the following permissions # ll -d /vagrant drwx------ 1 vagrant vagrant 612 Jun 13 ...
18
votes
3answers
68k views

How to run VMWare ESX or ESXi in a virtual machine?

Can VMWare ESX or ESXi be installed and used inside a virtual machine? It can be installed inside VMWare Workstation or Server, but then it doesn't work; the main symptoms are: It runs REALLY ...
18
votes
3answers
3k views

Virtual vs Physical Servers

I'm after a second opinion; and apologies if this has already been answered (point me in the right direction). Different factions within a project I'm on are engaged in a holy war between virtual vs ...
18
votes
6answers
39k views

How do you increase a KVM guest's disk space?

I setup an Ubuntu guest on a CentOS KVM host with initially 6GB of disk space. How do I go about increasing the Ubuntu guest's disk space from the command line? EDIT #1: I'm using a disk image file ...
18
votes
2answers
11k views

Is a 64 or 32-bit VirtualBox guest better on a 64-bit host?

On a 64 bit Windows7 machine will I get better VirtualBox guest performance running 32-bit or 64-bit Debian? I want to run the guest as a LAMP server.
17
votes
4answers
1k views

What are the benefits of “enterprise-level” virtualization?

For a company with modest virtualization needs - VirtualBox is currently doing fine at hosting a few light servers - what would some of the benefits be of moving to a more robust platform? I'm ...
17
votes
11answers
946 views

Windows desktop virutalization instead of replacing work stations

I'm head of the IT department at the small business I work for, however I am primarily a software architect and all of my system administration experience and knowledge is ancillary to software ...
17
votes
2answers
1k views

Can a virtualized machine have the CPU and RAM resources of multiple underlying physical machines?

We are studying implementing some virtualized servers here, but we don't know what will be better suitable for us. Some folks are saying better have two huge servers, and others are saying have like a ...
17
votes
10answers
21k views

Running 100 virtual machines on a single VMWare host server

I've been using VMWare for many years, running dozens of production servers with very few issues. But I never tried hosting more than 20 VMs on a single physical host. Here is the idea: A stripped ...
16
votes
11answers
26k views

VMware Linux Server — how can you tell if you are a vm or real hardware?

An interesting question. I have logged into a Linux (most likely SuSE) host. Is there some way that I can tell programmatically that I am a VM host or not? Also assume that the vmtools are not ...
16
votes
1answer
7k views

Hosting a ZFS server as a virtual guest

I'm still new to ZFS. I've been using Nexenta but I'm thinking of switching to OpenIndiana or Solaris 11 Express. Right now, I'm at a point of considering virtualizing the ZFS server as a guest within ...
16
votes
12answers
19k views

Is it possible to setup a virtual machine inside another virtual machine

I have been playing with virtual machines latley, and wondered if I could run a virtual machine inside a virtual machine? Is it possible? Is it practical?
15
votes
8answers
1k views

What are some good, free “virtual machine” apps? [closed]

I've been out of the virtual machine market for a while. Back in 2005, I used Microsoft Virtual PC 2004 (not free) and the current version of VMWare (not free). What are some good, free solutions? ...
15
votes
8answers
91k views

Hyper-V on Windows 7?

I'm running the new Windows 7 RC x64. I would like to set up a couple of virtual servers running on the same box as my desktop OS. I know that I can do this with some of the other virtualization ...
15
votes
4answers
13k views

Booting a native Windows install in Virtualbox: is it possible?

I am looking for something similiar to Bootcamp. Currently, I run Ubuntu Maveric as my primary operating system and run Windows 7 in Virtualbox. For some tasks, however, running Windows virtualized ...
15
votes
4answers
20k views

Is there a way to run virt-manager on Windows?

We've been using KVM for almost a year strictly on CentOS 5.x as the KVM host, with Fedora and Ubuntu workstations accessing the KVM host and its guests using virt-manager, virt-viewer, and ssh. Is ...
15
votes
5answers
3k views

Best Practices for virtualizing servers onto the SAN?

Alright, so I want to start leveraging my SAN a little more than I have been, and at the same time, take advantage of ESXi. Currently, I've got an array of Dell PowerEdge 1955 blades connected to a ...
14
votes
12answers
34k views

How do I know if I'm working on a Virtual Machine or not?

Is there a way to know if the Windows machine I'm working on is virtual or physical? (I'm connecting with RDP to the machine. If it's a virtual machine it is working and handled by VMWare).
14
votes
3answers
565 views

Active Directory Virtualization

My company is looking to try and virtualize all our servers, and we are trying to figure out if virtualizing active directory is a good idea. Is it even something that can be done, and if so are ...
14
votes
5answers
981 views

Choosing a SAN technology for 100s of VM Web Servers

The Problem We have an issue with performance on an existing platform, so I'm turning to the hive mind for a second opinion on this. The performance issue so far relates to IOPS rather than ...
14
votes
3answers
3k views

How can I set up VLANs in a way that won't put me at risk for VLAN hopping?

We're planning to migrate our production network from a VLAN-less configuration to a tagged VLAN (802.1q) configuration. This diagram summarizes the planned configuration: One significant detail is ...
14
votes
9answers
14k views

Is it possible/advisable to run VMware Server ESX/ESXi on a laptop?

The idea of having a small footprint hypervisor as the primary OS on a laptop or desktop where every "real" OS is a guest appeals to me. Now I realize this software is more typically used on blades ...
13
votes
4answers
702 views

Are production servers running as virtual images a good idea?

What are the risks of running a production web server and database in on a virtual server? Currently we are thinking of using VM Ware server. It seems like a nice solution that will lead to easy ...
13
votes
2answers
6k views

Difference between KVM and QEMU

I have been reading about them for sometime. As of now I have a clear understanding of what they do. KVM supports hardware virtualization to provide near native performance to the Guest Operating ...
13
votes
3answers
5k views

How is memory allocated in ESXi server?

We have an ESXi 4.1 server with 48 GB RAM. For each VM, we are allocating 4GB of memory. Since the server will have 13 virtual machines, my manager thinks this is wrong. I am going to explain to ...
13
votes
5answers
2k views

Considerations when chosing AMD processors over Intel

I work for a company with a lot of legacy LAMP web-applications, where we are trying to refresh our hardware from ~250 physical servers to ~40 new servers w/virtualization. We have received two ...
13
votes
3answers
2k views

Hyper-V Processor Limitations

We have recently purchased a server which is running Hyper-V 2008 R2 bare metal. The server has two quad-core Intel Xeon processors with hyperthreading, so if I'm understanding correctly this gives us ...
13
votes
6answers
2k views

recommendations for efficient offsite remote backup solution of vm's

I am looking for recommendations for backing up my current 6 vm's(and soon to grow to up to 20). Currently I am running a two node proxmox cluster(which is a debian base using kvm for virtualization ...
12
votes
10answers
569 views

How to convince management to deploy to Virtual Machines

How would you 'sell' using VMs for production application servers? What are the compelling benefits in using them in that situation? I have to maintain a number of applications that are critical but ...
12
votes
4answers
20k views

KVM: Which CPU features make VMs run better?

We are using Ubuntu 12.04 with the following parameters: Dell R910 Kernel 3.2.0-25-generic #40-Ubuntu SMP x86_64 x86_64 x86_64 GNU/Linux kvm 1:84+dfsg-0ubuntu16+1.0+noroms+0ubuntu13 qemu-kvm ...
12
votes
3answers
6k views

How much overhead does x86/x64 virtualization have?

How much overhead does x86/x64 virtualization (I'll probably be using VirtualBox, possbly VMWare, definitely not paravirtualization) have for each of the following operations a Win64 host and Linux64 ...
12
votes
9answers
1k views

When to move a virtualized server to physical?

Virtualization has some great benefits, but there are times when a virtualized server needs more performance and should be moved to physical. My question is, how do you tell when these times are? I'm ...
11
votes
6answers
3k views

Is virtualbox good for live server virtualization

I used virtual box before to test OS installation on my own personal computer. I'm not sure if it's suitable for actual virtualization on live servers. I mostly hear about Xen for that. Is virtualbox ...
11
votes
4answers
2k views

Can a virtual machine (VM) “hack” another VM running on the same physical machine?

Questions: if a VM is corrupted (hacked), what do I risk on others VMs running on the same physical machine? What kind of security issues is there between VMs running on the same physical host? Is ...