# `3-DC` in 2 Cities Deployment Solution

![`smart`](3DC2CitiesDeployment_aa_001_20221025.png)

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The plan for the 3 DCs in the 2 cities is similar to the the one with 3 DCs. 

It is considered that the 3 DCs plan is optimized according to the characteristics of the business. The difference is that the 3 DCs plan, DC is very close to each other (usually in the same city), and the network latency is relatively not outstanding. 

In this scenario (3-DC in 2 cities), we distribute business traffics to 2 data centers in the same city, and at the same time, deploy the `region leader` and `PD leader` also distributed to the same 2 data centers in the same city.

Compared with the 3 DCs center solution, the 3-DC in 2 cities plan has the following advantages:
- Better writes speed
- Two data centers provide services at the same time, the resource utilization is better
- Possible to guarantee that any data center will remain available and that there will be no data loss after failure

However, the disadvantage is that if two data centers in the same city fail at the same time (theoretically the probability is higher than losing 2/3 data cetners from 3 different cities at the same), it will lead to unavailability and partial data loss.