Load Balancer(LB)

LB can be applied in any layer above IP network.

scalability

Vertical(hardware) Scaling

CPU: L2 Cache Disk: SATA SAS SSD

PATA

RAM:

Horizontal scalling

Cheaper hardware

Distributed backend server. Load balancer

DNS return IP of load balancer

BIND: heuristic: round roubin policy.

Caching: TTL 1 hrs.

Storing sessions in load balancer. File server with the same session

RAID drive

RIAD0 : strip write for performance RAID1: two drives redundancy. RIAD10: Striping and redundancy 4 drives. RAID5:One drive can die RAID6:Any two drives can die.

Robustness and redundancy.

How to solve Downtime problem?

replication issue.

Software

ELB HAProxy LVS

Hardware

Barracuda Cisco Citrix 100K F5

Sticky Sessions

Layer 7 load balancing

Shared Storage

FC, ISCSI, MySQL, NFS.

Cookies in Load balancer

Storing the ID of the server in cookies Store big random number in the load balancer.