HI,
I have over 10 Years system administration experience. I can setup HA-Proxy LB with HA to accomplish your requirement.
Relevant Skills and Experience
RHEL-4,5,6,7/CentOS-6,7, Debian, Ubuntu, Windows 2008, 2012
VMWare Esxi-5.x,6.x, XenServer, ProxMoxVE
MySQL Replication and Cluster Setup
PCI compliant LAMP Stacks
AWS, Google Cloud
Answer to Your Queries:
1) how you will make this?
OpenSource HA Proxy - Load Balancer
KeepAlived - For HA
Apache/Nginx - To manage your Web Page
2) How long it will take?
Less than 8 Hours.
3) How many server we need?
Minimum 4 Virtual Servers.
4) What os?
Centos-7 or Ubuntu/Debian which ever is comfortable for you.
Proposed Milestones
€61 EUR - Load Balancer Setup and configuration
Due of word limit in Freelancer, it's difficult to elaborate in detail. If you are interested we can use Freelancer chat/skype/email.
PS: I've upload a small brief article about a simple HA-Proxy implementation along with pictorial representation under my portfolio. Please do check and let me know if you are interested. :)