Kieran Jacobsen 14/6/11 Kieran Jacobsen 14/6/11

Windows Server 2008 R2 + LVS with Direct Routing and Windows Firewall

For those of you who are in the need for an IP LoadBalanacer, and do not want to pay for an F5, check out the LVS project.

We recently set up a number of LVS balanced pages, and quickly came into difficulty in selecting thr routing method used. We struggled to find documentation, and were told to use the NAT technique, something that we were not happy with. The lack of documentation was also not helped due to the fact we wanted to load balanced Windows 2008 R2 servers running IIS 7.5.

We managed to work out how to set up both the Linux side of the fence (the machines running LVS) and then what to do on the Windows Servers being balanced. We also managed to leave the Windows Firewall on!

Once you have your LVS setup running. Perform the following steps to

1. Perform the standard configuration using what ever method you like (Piranha the web interface is brilliant for this) and ensure you select "Direct Route"

2. Restart Pulse service

3. Add the Loop back adapter to each Windows machine as specified at DR and LV Tun Clusters

4. You do not need to disable the Windows Firewall

5. Setup weak host send and recieve as specified at the loadbalancer blog.

Kieran Jacobsen 11/6/11 Kieran Jacobsen 11/6/11

Powershell Script Template

Just a quick post to cover layout/format of all PowerShell scripts I write.

This default template ensures that a sufficient amount level of of quality is ensured in all scripts. There are several things you will notice:

All scripts start with param definitions, which include items for the functionality for that script (both mandatory and option) as well as variables used to support features other basic functions
Email alerting on success of failure with option to turn off or on both, either, or no email alerts
I use exit calls, I know this is probably considered bad, but as you can see, it makes it easier to troubleshoot

And here it is (you can download it here):

# ==============================================================================================
#
# Microsoft PowerShell Source File -- Created with SAPIEN Technologies PrimalScript 2009
#
# NAME: <name of script which will be helpful>
#
# AUTHOR: <author>
# DATE : <date>
#
# COMMENT: <Step through what this script does
#
# ==============================================================================================

#<place comments used to assist in the calling of the script

param(
   #<application specific params>

   #<email and alerting params>
   [Parameter(Position=3, Mandatory=$false, HelpMessage="Specify email alert recipient address")]$recipient="[email protected]",
   [Parameter(Position=4, Mandatory=$false, HelpMessage="Specify email alert from address")]$from="[email protected]",
   [Parameter(Position=5, Mandatory=$false, HelpMessage="Specify smtp server name/ip")]$smtpserver="smtp.server.com",
   [Parameter(Position=6, Mandatory=$false, HelpMessage="Alert on sucessfuly copy")]$emailonsuccess=$true,
   [Parameter(Position=7, Mandatory=$false, HelpMessage="alert on failure of copy")]$emailonfailure=$true,
   [Parameter(Position=8, Mandatory=$false, HelpMessage="alert email subject")]$emailsubject="<change to be helpful subject>"
)

#
#variable declarations


function send-email ($body, $success)
{
   #incase we are troublshooting, output the body here
   $body

   $error.clear()
   #if it is sucessful
   if ($success)
   {
       #if we want a successful emails
       if ($emailonsuccess)
       {
           $subject = $emailsubject + "- Success"
           Send-MailMessage -To $recipient -From $from -SmtpServer $smtpserver -Subject $subject -Body $body -bodyashtml
       }
   }
   else #if unsuccessful
   {
       #if we want emails on failure
       if ($emailonfailure)
       {
           $subject = $emailsubject + "- Failure"
           Send-MailMessage -To $recipient -From $from -SmtpServer $smtpserver -Subject $subject -Body $body -bodyashtml
       }
   }

   if ($error)
   {
       "Unable to send an email"
       exit 666
   }
}

#
# If we expect a crash/error here is an example (this is using $error but it could be try catch or based on $lastexitcode for external calls
#
$error.clear()
#do something bad
somethingbad()
if ($error)
{
   send-email "<sad>" $false
   exit 7
}

#email that we got here successfully
send-email "<HAPPY>" $true