Created Async Replication to another Filer (markdown)

Async-Replication-to-another-Filer.md

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+# Architecture
+
+![](FilerAsyncReplication.png)
+
+# How it works
+
+There should be two Seaweed File Systems running, possibly across data centers. Each should have its filer, master, and volume servers.
+
+## Configuration
+* Configure notification. use "`weed scaffold -config=filer`" to see the notification section.
+
+```
+[notification.log]
+enabled = true
+
+[notification.kafka]
+enabled = false
+hosts = [
+  "localhost:9092"
+]
+topic = "seaweedfs_filer1_to_filer2"
+
+```
+
+* Setup Kafka. Possibly you need to create the Kafka topic if auto topic creation is not enabled.
+
+* Configure replication. use "`weed scaffold -config=replication`" to see the notification section.
+
+```
+[source.filer]
+enabled = true
+grpcAddress = "localhost:18888"
+directory = "/buckets"    # all files under this directory tree are replicated
+
+[notification.kafka]
+enabled = true
+hosts = [
+  "localhost:9092"
+]
+topic = "seaweedfs_filer1_to_filer2"
+
+[sink.filer]
+enabled = true
+grpcAddress = "localhost:18888"
+directory = "/backup"    # all replicated files are under this directory tree
+replication = ""
+collection = ""
+ttlSec = 0
+
+```
+
+Please read the source.filer and sink.filer configurations carefully and make sure you fully understand its intention. This is actually using one filer and replicate files from one folder to another folder.
+
+* Start the replication. "`weed filer.replicate`"