VM Sprawl is a PITA.  We've gone there a little bit.  That said, I *think* the 
management overhead is outweighed by the application isolation, but it's been 
something I'm aware of.

RAM - honestly, they need what they need, you don't change the physics just 
because it's virtualised, if an app needs 2gb on a physical box it'll need 2gb 
on a VM.

The difference is how easily you can tweak it - buy a physical box and you need 
to know how much physical RAM to buy, buy 16gb and it only uses 4gb that's 12gb 
($$) doing nothing, do that with a VM and you shut it down, bump down the RAM, 
power it back on, job done.

Honestly, if you just want a number then from what you've said chuck 96gb or so 
in the box and you'll be good.

-----Original Message-----
From: Ben Scott [mailto:[email protected]] 
Sent: 02 December 2011 21:33
To: NT System Admin Issues
Subject: Re: Virtualization - Sizing, hard disk config

On Fri, Dec 2, 2011 at 4:02 PM, N Parr <[email protected]> wrote:
> Plan your build to put every service on it's own VM ...

  I'm planning on putting each critical service set on its own VM.
But things like the anti-virus software, WSUS, things like that -- they can 
reboot without impacting operation.  Even BES can usually be down for 10-15 
minutes without anyone noticing.

  But each VM has costs associated with it, not just for hardware, but 
management overhead, too.  Dedicating a VM to a database used by two people a 
few times a week, and which has a peak working set of 15 megabytes, doesn't 
seem sensible.

> ... give them the the RAM they need.

  And how much is that?  That's my question.  How much do they need?  :)

> Don't skimp with by provisioning 1GB of ram on an 08R2 server.

  Okay, so is 2 GB enough for a DC handling 120 PCs?  4 GB?  :)

> You've got to build out your infrastructure to allow for growth or you 
> be back at the boss' door begging for more $$.

  Sure.  Valid point.  So let's say, for the DC, we double to 240 PCs,
200 accounts, and a whopping 200 MB NTDS.  Is that going to blow the 2 GB DC 
out of the water, then?  :)

  I *do* want to plan this correctly.  But just "get enough RAM" isn't a plan.  
:)

-- Ben

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