# Replication method consideration

**URL:** <https://forums.foundationdb.org/t/replication-method-consideration/1410>\
**Category:** Using FoundationDB\
**Created:** [May 30, 2019, 12:13pm UTC](https://forums.foundationdb.org/t/replication-method-consideration/1410 "2019-05-30T12:13:55Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Choboz](https://avatars.discourse-cdn.com/v4/letter/c/65b543/32.png) [@Choboz](https://forums.foundationdb.org/u/Choboz)\
**Post date:** [May 30, 2019, 12:13pm UTC](https://forums.foundationdb.org/t/replication-method-consideration/1410/1 "2019-05-30T12:13:55Z")

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Hi! I have five data centers with three instances in each DC, and I need to have the possibility to write/read data in/from each data center. So which replication method I should prefer? Is three\_datacenter method will fulfill my needs or I need to choose region configuration instead?

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**Author:** ![alexmiller](https://sea1.discourse-cdn.com/foundationdb/user_avatar/forums.foundationdb.org/alexmiller/32/326_2.png) [@alexmiller](https://forums.foundationdb.org/u/alexmiller)\
**Post date:** [May 31, 2019, 12:39am UTC](https://forums.foundationdb.org/t/replication-method-consideration/1410/2 "2019-05-31T00:39:24Z")

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We don’t have a great answer to having one cluster that offers \>1 DC of fault tolerance yet.

Though it’s theoretically possible to run three\_datacenter mode with more than three datacenters, I think we discovered that an assertion will accidentally fail if you try and run it with \>3 datacenters, thus proving that no one has tried to so far. Three datacenter mode will eventually be deprecated in favor of multi-region, but multi-region currently only supports 2 regions at most.

The only way to utilize your hosts right now would be to do a multi-region cluster of using two of the DCs as primary and secondary, a third DC as a satellite, and leave the other two not specified in the region configuration.

So if you need a failure tolerance of 2 or more datacenters, I think FDB isn’t a good fit for your use case right now, and I’d suggest checking back in two or three releases from now when we’ve hopefully made sufficient progress on multi-region supporting more than two regions.

Do note that any of the available options will give high write latency for all but one of your DCs (the primary), and non-stale reads will still require one round trip to the primary to get a read version. Depending on how you meant “read/write in/from each datacenter”, that may or may not match what you require anyway.