Change the settings to enable Dynamic template mode and create a new setting for testing purpose:
Use different settings on server1 and server2

For server1, use:
./settings/override/site.ini.append.php
[eZINISettings]
DynamicTemplateMode=enabled
 
[QASettings]
OurCompany=eZ Systems_cluster1

For server2, use:
./settings/override/site.ini.append.php
[eZINISettings]
DynamicTemplateMode=enabled
 
[QASettings]
OurCompany=eZ Systems_cluster2


On both servers, do the following actions, except creating the article, that can be done in only one of them
Create an Override on the Template
- Log in as admin in admin interface
- Click "Setup" in top menu
- Click "Templates" in the left menu
- Select "/node/view/full.tpl"
- Click on “New Override” button
  Extension:  No Extension
  Filename: validate_ini
  Class: article
  Base template on: View (Without Children)
-Press “ok” button
- Click on edit template button
- Add the following code to the end of the existing code
  <br/>
  our setting : {ezini( "QASettings", "OurCompany", "site.ini" )} 
  <br/>
- Click on “Apply changes” button
 
Create an article 8thsi can be done in only one of the servers)
- Create an article "Article 1"
- Before exiting, clear **all** caches
- Logout
 
Verify results on Server1
- Access the plain site on server1
- Click on “article 1" link
- Verify that, in the bottom of the page, the value of the ini file attribute is: eZ Systems_cluster1

Verify results on Server2
- Access the plain site on server2
- Click on “article 1" link
- Verify that, in the bottom of the page, the value of the ini file attribute is: eZ Systems_cluster1 (this is correct, because the data being used it's the shared cache generated when we viewed the article in Server1)

Clear cache in server1 (not in server2), *without* using "--purge' option
 $ php  bin/php/ezcache.php --clear-tag=content
 
Verify results on Server2
- Access the plain site on server2 again
- Click on “article 1" link
- Verify that, in the bottom of the page, the value of the ini file attribute is: eZ Systems_cluster2 (In this point, the value that i'm having is still "Systems_cluster1", as if the cache was not cleared. Where is this value being fetched?)

Clear cache in server1 (not in server2), using "--purge' option
 $ php  bin/php/ezcache.php --clear-tag=content --purge
 
Verify results on Server2
- Access the plain site on server2 again
- Click on “article 1" link
- Verify that, in the bottom of the page, the value of the ini file attribute is: eZ Systems_cluster2 (Now the value is the expected one)