[CentOS] New to VM

nate centos at linuxpowered.net
Thu Mar 4 03:41:03 UTC 2010


David Milholen wrote:
> I have managed these for so long on just a couple of machines but
> technology is changing and we are growing as a company and I have heard
> and read great things that can be done with VM.

Really depends on how much usage the systems get, if you are migrating
from physical systems to virtual systems look at the CPU, load, and
i/o(if linux use iostat). I run vmware server on a 5-year old system
which has 2 VMs on it, runs apache, mysql, mail services, dns, and
a bunch of other small things. Works fine, though my typical CPU
usage on the *host* is 5%. Running off a pair of 250GB SATA drives
connected to a 3Ware 8006-2 RAID card. Dual Xeon 3Ghz, 6GB ram, 32-bit.

In my experience most systems like the ones your using hosting
the apps you mention are idle 99%+ of the time, making them perfect
VM candidates.

> I have another ibm Eserver with a couple of scsi 15k 50GB drives and 4
> GB of memory that I can configure from scratch to do VM or what ever I need.
>  I guess I should start by asking how VM is configured and How does
> allocate resources on the server?

Resource allocation depends on the VM technology your using, myself
I am a long time VMware fan/user, so I stick to their stuff, but
no matter what it really depends on how much load your system  will
be under.

>From a VMware perspective, this PDF is informative, but probably
well beyond the scale your operating at, you can get an idea as
to the complexity that "virtualization" entails.

http://portal.aphroland.org/~aphro/vmware/09Q3-perf_overview_and_tier1-pac_nw.pdf

Performance of bare metal hypervisors like VMware ESX will
dramatically outperform the hypervisors that run on top of
another OS(I think they call them "type 2") like VMware server.
But bare metal hypervisors have very strict hardware requirements.
I use VMware server on my own system since the hardware is not
supported by ESX.

At my full time job I run dozens of ESX systems on real hardware,
with a proper SAN and networking infrastructure.

nate



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