HeimingZ commented on a change in pull request #5320:
URL: https://github.com/apache/iotdb/pull/5320#discussion_r839356089
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File path: server/src/assembly/resources/conf/iotdb-engine.properties
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@@ -65,25 +65,44 @@ config_nodes=127.0.0.1:22277
### Write Ahead Log Configuration
####################
-# Is insert ahead log enable
-# Datatype: boolean
-# enable_wal=true
+# Write mode of wal
+# The details of these three modes are as follows:
+# 1. DISABLE: the system will disable wal.
+# 2. SYNC: the system will submit wal synchronously, write request will not
return until its wal is fsynced to the disk successfully.
+# 3. ASYNC: the system will submit wal asynchronously, write request will
return immediately no matter its wal is fsynced to the disk successfully.
+# The write performance order is DISABLE > ASYNC > SYNC, but only SYNC mode
can ensure data durability.
+# wal_mode=SYNC
+
+# Duration a wal flush operation will wait before calling fsync
+# A duration greater than 0 batches multiple wal fsync calls into one. This is
useful when disks are slow or WAL write contention exists.
+# Datatype: long
+# fsync_wal_delay_in_ms=0
-# Add a switch to drop ouf-of-order data
-# Out-of-order data will impact the aggregation query a lot. Users may not
care about discarding some out-of-order data.
-# Datatype: boolean
-# enable_discard_out_of_order_data=false
+# Max number of wal nodes, each node corresponds to one wal directory
+# The default value 0 means the concurrent wal number will be 2 * 'number of
wal dirs'.
+# Datatype: int
+# max_wal_node_num=0
-# When a certain amount of insert ahead log is reached, it will be flushed to
disk
-# It is possible to lose at most flush_wal_threshold operations
+# Buffer size of each wal node
+# If it sets a value smaller than 0, use the default value 16777216 bytes
(16MB).
# Datatype: int
-# flush_wal_threshold=10000
+# wal_buffer_size_in_byte=16777216
-# The cycle when insert ahead log is periodically forced to be written to
disk(in milliseconds)
-# If force_wal_period_in_ms = 0 it means force insert ahead log to be written
to disk after each refreshment
-# Set this parameter to 0 may slow down the ingestion on slow disk.
-# Datatype: long
-# force_wal_period_in_ms=100
+# Buffer entry size of each wal buffer
+# If it sets a value smaller than 0, use the default value 16384 bytes (16KB).
+# Datatype: int
+# wal_buffer_entry_size_in_byte=16384
+
+# Max storage space for each wal node
+# Notice: If this parameter is too small, the write performance may decline.
+# Datatype: int
+# wal_node_max_storage_space_in_mb=3072
Review comment:
This parameter is used to control disk usage, not memory usage.
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