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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77
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4answers
14k 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 ...
57
votes
7answers
6k 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 ...
51
votes
10answers
14k views

How to [politely?] tell software vendor they don't know what they're talking about

Not a technical question, but a valid one nonetheless. Scenario: HP ProLiant DL380 Gen 8 with 2 x 8-core Xeon E5-2667 CPUs and 256GB RAM running ESXi 5.5. Eight VMs for a given vendor's system. ...
50
votes
9answers
113k 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 ...
47
votes
3answers
4k 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 ...
45
votes
2answers
3k 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, ...
38
votes
2answers
50k 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 ...
37
votes
5answers
77k views

Top - what does Virtual memory size mean? …linux/ubuntu

I am running top to monitor my server performance and 2 of my java processes show virtual memory of up to 800MB-1GB. Is that a bad thing? What does virtual memory mean? And oh btw, I have swap of ...
36
votes
5answers
31k 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 ...
36
votes
7answers
22k 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 ...
36
votes
10answers
4k views

Linux on VMware - why use partitioning?

When installing Linux VMs in a virtualized environment (ESXi in my case), are there any compelling reasons to partition the disks (when using ext4) rather than just adding separate disks for each ...
33
votes
6answers
64k 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 ...
32
votes
12answers
28k 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 ...
31
votes
2answers
20k views

Difference between KVM and QEMU

I have been reading about KVM and Qemu 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 ...
31
votes
5answers
8k 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 ...
28
votes
11answers
3k 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
4answers
753 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 ...
25
votes
8answers
3k views

Consumer (or prosumer) SSD's vs. fast HDD in a server environment

What are the pro's and con's of consumer SSDs vs. fast 10-15k spinning drives in a server environment? We cannot use enterprise SSDs in our case as they are prohibitively expensive. Here's some notes ...
22
votes
12answers
59k 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).
22
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?
21
votes
12answers
41k 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 ...
21
votes
6answers
6k views

Can windows domain controller be virtualized?

Just the question on the title. There is any problem? Any experience on this?
20
votes
4answers
2k views

How much contention is too much in VMware?

For a while now I've been trying to figure out why quite a few of our business-critical systems are getting reports of "slowness" ranging from mild to extreme. I've recently turned my eye to the ...
20
votes
1answer
15k 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 ...
20
votes
3answers
77k 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 ...
19
votes
10answers
34k 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 ...
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
1answer
11k 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 ...
18
votes
5answers
715 views

Is there a reason to give a VM a round base-2 amount (2048MB, 4096MB, etc) of memory?

The title pretty much says it all, is there any advantage to giving a VM 2048MB of memory instead of rounding to base-10 and doing 2000MB?
18
votes
2answers
13k 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.
18
votes
1answer
559 views

Virtualized MS-DOS computers can't communicate over IPX

I converted 2 MS-Dos 6.22 machines to virtual machines. Both computers have software that communicates over NETBEUI and IPX (I came to that conclusion after inspecting autoexec.bat - It loads IPX ...
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
986 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
8answers
99k 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 ...
17
votes
12answers
25k 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?
17
votes
4answers
31k 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 ...
16
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 ...
16
votes
4answers
33k 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 ...
16
votes
1answer
18k views

KVM and Libvirt - How do I hotplug a new virtio disk?

I am trying to hot-add a file-based disk to a running KVM virtual server. I've created a new disk from scratch using the command dd of=/home/cloud/vps_59/test.img bs=1 seek=5G count=0 and I was ...
16
votes
2answers
1k views

Is running permanently in a VMWare snapshot bad for performance?

I understand that the VMWare KB frowns upon long running snapshots mainly due to two things (In my opinion) Taking tons of snapshots can fill up the data store. Snapshots are simply delta files. ...
16
votes
3answers
9k 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 ...
16
votes
4answers
14k 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 ...
16
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 ...
15
votes
6answers
5k 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 ...
15
votes
10answers
7k views

Are there any good reasons for disabling hardware-assisted virtualization?

We've had a number of servers from Dell recently, all of which have had hardware-assisted virtualization disabled in the BIOS. As far as I know hardware-assisted virtualization is a good thing - so ...
15
votes
5answers
19k views

How to zero fill a virtual disk's free space on windows for better compression?

How to zero fill a virtual disk's free space on windows for better compression? I would like a simple open source tool (or at least free) for that. It should probably write an as big as possible file ...
14
votes
3answers
584 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
1k 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
4k 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
17k 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 ...