This is the primary computer where all your new information is saved first. It acts as the source of truth for the rest of the system.

The Main Data Copy

These are exact duplicates of your data kept on different machines. They are ready to step in if the main copy has a problem.

The Backup Data Copies

Keeping multiple copies ensures your information isn't lost if a computer breaks. It also makes the system faster by sharing the workload.

Why We Copy Data

This is when the system waits for every copy to be updated before confirming a save. It is the safest method but can feel a bit slower.

Instant Data Syncing

The main computer saves your data quickly and sends updates to the backups later. This is very fast, but a few seconds of data might be lost if a crash occurs.

Delayed Data Syncing

Also known as lag, this is the tiny delay between saving data on the main server and it appearing on the copies. Usually, this happens in less than a second.

The Update Gap

This is the goal of making sure every copy shows the same exact information. It prevents users from seeing old or conflicting data.

Keeping Information Consistent

If the main computer fails, the system automatically promotes a backup to take its place. This keeps the service running without a human having to fix it manually.

Automatic Disaster Switch

Computers in the network send 'heartbeat' signals to each other constantly. If a signal stops, the others know that computer has crashed and needs to be replaced.

System Health Checks

High availability is a measure of how often a service is working and accessible. The goal is to be available 99.999% of the time, or almost every minute of the year.

Always On Uptime

This refers to any one part of a system that, if it breaks, causes the whole thing to fail. Good systems use replication to remove these dangerous weak spots.

The Single Point Weakness

By putting copies in different cities or countries, data travels a shorter distance to reach the user. This makes websites and apps feel much faster.

Bringing Data Closer

This is like taking a digital photograph of all your data at a specific moment. It is used as a safety net to restore information if something goes wrong.

Point In Time Snapshots

In some advanced setups, several computers can accept new information at the same time. They then talk to each other to make sure all copies stay synchronized.

Multiple Leaders Working Together

When a computer that was broken comes back online, it automatically asks the other machines for the updates it missed. This ensures it is back in sync with the group.

Automatic Data Healing

This involves keeping copies in entirely different geographic regions. It protects your data even if a whole data center is hit by a power outage or natural disaster.

What is Always On?