[mdlug] Virtual Server Time

[Carl T. Miller]

Robert Adkins II wrote:
>> If the
>> goal is to recover from a borked host quickly, shared storage
>> makes more sense.  We can discuss this further if desired.
>
> 	I would like to learn more about NAS, it's just not been something
> high on my list, as the pricing had been out of reach of the budget that I
> typically have available. It's a very interesting concept and I think it
> would suit my needs quite well. I believe there is also some additional
> benefit with backing up data, data throughput and restoring/replacing the
> NAS in cases of catastrophic failure.

NAS options for the small scale would include small devices
that hold 4 drives, a dedicated server, or even just selecting
glusterfs for the hosts.  There are more expensive options,
but this isn't bad for a starting point.

>> This would not be needed if you have shared storage and you
>> keep your servers running.  Otherwise you'd just need
>> instructions to power on the reserve server and do everything
>> else remotely.
>
> 	This is another benefit of NAS that I would be interested in
> learning more about.

As long as you have access by ssh to each of your hosts,
you can run commands to move a guest from one host to another.
While a "live migration" would require expensive hardware,
you could rather easily connect to a live server and start
a guest which had been running on another host.

>> My first suggestion is to be sure to use LVM on any and all
>> partitions of your physical hard drives (with the notable
>> exception of /boot).  If possible, keep between 20% and 40%
>> unused so you can expand partitions as needed.
>>
>
> 	LVM on the Virtual Machines or on the drives that will hold the VMs
> or the drives that will hold the data? I have been using a very effective
> for me drive layout for a little over 10 years now, it's evolved slightly,
> but I have never run into any issues with it. There are probably a few
> ways to do some elements better though.

I recommend it for both hosts and guests.  LVM provides options
like resizing partitions and hot migration of a failing disk.
All you need to do is extend a / partition live on a produciton
server one time, and you'll be sold!

> 	This is how I intend on configuring the VMs
>
> 	1. Email/Proxy Server/DNS
> 		This one will handle the basic MTA, the IMAP service, DNS
> and run Squid. It's going to be one of two machines that can "see" outside
> of the network.
>
> 	2. SSL Email Server
> 		I am particular to a particular MTA and it's going to be
> easier, for now, to setup a MTA that uses SSL asa  "full" separate server.
> This one will also "see" outside of the network.
>
> 	3. File Server/Account Management Server
> 		Windows Domain Controller and I plan on consolidating all
> user account information onto this server as well with all other VMs
> asking this server for user authentication.

This plan looks good.  The only thing I would do is set up
the DC first and see what resources it eats up.  Give it at
least a week and analyze sar data carefully.  Depending on
the number of users and the usage, you may not want to add
the other vms to this host.

c