[ale] What are the minimum requirements for a CentOS server to learn on?

[Brian Pitts]

On 05/04/2010 06:04 PM, Greg Freemyer wrote:
> I'm not sure the RAM overhead of VMs was emphasized.
> 
> VMs use require dedicated RAM so it is a major driver.
> 
> Lets say you want to have a host and 4 simultaneously running VMs.
> 
> I would think 512MB minimum for each, so you need 2.5GB for that.

Memory is cheap, and it's always good to have more. I probably wouldn't
buy anything with less than 4GB. That said, you could get away with a
lot less than that and still experiment with a decent number of vms.

1) KVM supports overcommiting memory. Booting a centos vm might take
100MB. Even if I've allocated 200MB to it, it will only use 100MB on the
host.

2) Kernel 2.6.32 and later support Kernel Samepage Merging (yep, that
means it's in RHEL6). This deduplicates memory, meaning that if I run 10
VMs that have 90% the same memory contents they will use only 190% of
the memory that running one VM uses.

> And if the host is really a desktop machine running
> X/KDE/firefox/etc., I'd go with 2GB for the desktop use, and 512MB for
> each server VM.
>
> And each VM will want 50GB or so minimum of disk, so that's 250GB.

That's pretty generous.

I just checked one RHEL5 VM running nagios and apache and another
running gnome with firefox, a terminal, and that memory hog xemacs.

Disk usage is 1.5GB for the server and 2.5GB for the desktop, not
including swap.

Memory usage is 80MB and 283MB not including buffers and cache, 247MB
and 703MB with them included.

-- 
All the best,
Brian Pitts