# Fairly large time to become available after fallback in a multi region FDB

**URL:** <https://forums.foundationdb.org/t/fairly-large-time-to-become-available-after-fallback-in-a-multi-region-fdb/4915>\
**Category:** Running FoundationDB\
**Created:** [May 22, 2025, 9:18pm UTC](https://forums.foundationdb.org/t/fairly-large-time-to-become-available-after-fallback-in-a-multi-region-fdb/4915 "2025-05-22T21:18:43Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![mpatou\_openai](https://sea1.discourse-cdn.com/foundationdb/user_avatar/forums.foundationdb.org/mpatou_openai/32/1883_2.png) [@mpatou\_openai](https://forums.foundationdb.org/u/mpatou_openai)\
**Post date:** [May 22, 2025, 9:18pm UTC](https://forums.foundationdb.org/t/fairly-large-time-to-become-available-after-fallback-in-a-multi-region-fdb/4915/1 "2025-05-22T21:18:43Z")

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Yesterday we ran a test for failover and fallback of FDB, failover went fairly smoothly.  
But fallback not as much.  
We had a setup with 2 FDB regions each with a main (where you have the whole set of roles/processes: storage, log, coordinators & stateless) and a satellite.  
In the region with the highest priority we disconnected the main completely causing FDB to automatically fall back on the second region.  
Around 3:31PM pst we re-enabled the main in high priority region for roughly ~10 minutes the cluster was stable with all stateless roles still in the lower priority region (ie. controller, master, datastributor, GRV, Commit, …) and then around 3:45PM the roles switched back to the main region, data distributor realized that there was 60GB of data to move and then the DB started to unavailable for ~45 mins.

When I look at the logs it’s not quite clear what really triggered the database to become unavailable, looking at the logs \>= 20 it seems that it’s somewhat aligned with

```auto
{"date":1747867494.564181,"ID":"0000000000000000","Error":"transaction_timed_out","Roles":"CC","ErrorDescription":"Operation aborted because the transaction timed out","ErrorCode":"1031","Severity":"20","Machine":"10.129.2.168:4500","DateTime":"2025-05-21T22:44:54Z","Type":"LayerStatusError"}

```

I don’t have a final opinion on why the DB was not available for 45 minutes but I have the feeling looking at the \>10 logs that the storage in the main high pri region were lacking some critical data that prevented the DB from being available in this region.

The corollary question is: should FDB fall back to the primary region even if this one is not ready ?