[kwlug-disc] Virtualization allocation?

unsolicited unsolicited at swiz.ca
Sat Nov 6 16:54:26 EDT 2010


Paul Nijjar wrote, On 11/06/2010 4:18 PM:
> On the other hand, experiencing the joys of VM sprawl firsthand might
> be fun, too.

It gets old surprisingly, astonishingly, and depressingly, fast. vm 
sprawl is a pain in the arse. That many more machines to track, patch, 
monitor.

> It does not seem as if it is worth putting a lot of $$$
> into hardware for it (at least not on the Linux side).

It is always worth putting $ into redundant hardware (+ backups). 
Although perhaps only from an admin sanity point of view (eventually - 
once past the additional maintenance layer added).

However, one has to have the $ in the first place.

And the optics of it, to management, aren't good. A couple million $ 
into real multi-site redundant hardware, against what else the money 
could be used for.

It really comes down to policy decisions as to how important to your 
business live 24x7 access to your data is, and, especially, getting 
RTO and RPO targets set. RTO and RPO is easy to explain, easy to get 
(policy) decisions on, and lead almost directly to specification 
requirements that can be signed off on.

However, once they see the costs associated with effecting those 
decisions, the objectives tend to get ratcheted back. (-:

One thing frequently forgotten in such plans is room modifications - 
be it to accommodate more individual boxes (which don't tend to stack 
high / utilize height) - more square footage and electrical  and 
network connections, or to intensify per foot computing 'power' 
(racks) - adding 220v lines / power distribution units, etc.

	Fortunately, such costs, even if you're knocking down walls, tend to 
be one offs. But you sure don't want to be doing it twice.

Since increasing room space is frequently not possible, and computing 
requirements are only ever going to go up, you will be going to vm's 
some day. Knowing that, even if it's not coming tomorrow, may help you 
not snooker yourself for later.

So, if the big, bad, hardware, comes in - vm it up front. In the 
meantime, if you have separate working boxes, or are prototyping, keep 
them as separate boxes - knowing that when they become business 
critical, or production, they will move to a vm.

The problem is not vm, it's accommodating requirements in the space 
available, and those requirements include extent of redundancy, and 
supporting elements - be it power, ups, or connectivity.

Really, the RPO/RTO drive the rest.

It is perhaps not wrong to say that RTO/RPO / redundancy / uptime, 
drives vm. Big costs to the former drive maximizing the use of what 
those costs purchased.

Alternately, perhaps more true in your case, today's dual core 
hardware running functions/servers that don't tax the hardware feel 
ridiculous, so you try to run a few vm's rather than pulling out Yet 
Another Box. So instead of a massive vm / redundancy strategy, you 
have multiple smaller 'vm clusters' to take advantage of the disparate 
/ 'powerful' boxes available to you. Just remember, LOTS of memory - 
and sometimes it's easier to stuff 16GB memory in one box, than 4GB in 
4 boxes.

I suspect, in your case, you need multiple vm strategies, let alone 
bringing puppet into the mix, as you note. One strategy for whatever 
redundant hardware / production you have, and another to make best use 
of individual powerful boxes you might have.

If after a certain yardstick of hardware power is reached, you make a 
policy of always enterprise virtual boxing the hardware (you don't 
install an os, you install a vm managing low level upon which you 
install os'), perhaps life gets a little simpler / less complex, 
moving forward. [I'm thinking vmware esx, here - can't think of the 
name of the virtualbox equivalent.]



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