polish titan doc

Signed-off-by: tonyxuqqi <tonyxuqi@outlook.com>
pingcap · qiancai · Jan 25, 2024 · Jan 5, 2024 · Jan 5, 2024 · Jan 8, 2024
commit 331bfe130f924a80fd6a3871860155ea0041f65c
diff --git a/storage-engine/titan-configuration.md b/storage-engine/titan-configuration.md
@@ -75,6 +75,10 @@ To adjust Titan-related parameters using TiUP, refer to [Modify the configuratio
     [rocksdb.defaultcf.titan]
     min-blob-size = "1KB"
     ```
+
+> **Warning:**
+>
+> When the value is set less than `32KB`, the TiKV scan performance may have regression comparing with RocksDB. But if the workload is more about point get or heavy write, the `min-blob-size` can be tuned to as low as `1KB`. And therefore, starting from v7.6.0, the default value for newly create cluster is `32KB`, but to keep the behavior consistent for upgraded clusters, this parameter will keep the old version's default  `1KB` when it's not explictly set in configuration file.
 
 + The algorithm used for compressing values in Titan, which takes value as the unit. Starting from TiDB 7.6.0, the default compression is zstd.
 

diff --git a/tikv-configuration-file.md b/tikv-configuration-file.md
@@ -1600,10 +1600,14 @@ Configuration items related to `rocksdb.defaultcf.titan`.
 ### `min-blob-size`
 
 + The smallest value stored in a Blob file. Values smaller than the specified size are stored in the LSM-Tree.
-+ Default value: `"1KB"`
++ Default value: `"32KB"`
 + Minimum value: `0`
 + Unit: KB|MB|GB
 
+> **Warning:**
+>
+> When the value is set less than `32KB`, the TiKV scan performance may have regression comparing with RocksDB. But if the workload is more about point get or heavy write, the `min-blob-size` can be tuned to as low as `1KB`. And therefore, starting from v7.6.0, the default value for newly create cluster is `32KB`, but to keep the behavior consistent for upgraded clusters, this parameter will keep the old version's default  `1KB` when it's not explictly set in configuration file.
+
 ### `blob-file-compression`
 
 + The compression algorithm used in a Blob file