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Co-authored-by: Ran <huangran.alex@gmail.com>
pingcap · qiancai · Jan 25, 2024 · Jan 5, 2024 · Jan 5, 2024 · Jan 8, 2024
commit 02d78bbc2cc8029b4cb8290cc6a59185a8c4e940
diff --git a/storage-engine/titan-configuration.md b/storage-engine/titan-configuration.md
@@ -129,7 +129,7 @@ To disable Titan, you can configure the `rocksdb.defaultcf.titan.blob-run-mode`
 - When the option is set to `read-only`, all newly written values are written into RocksDB, regardless of the value size.
 - When the option is set to `fallback`, all newly written values are written into RocksDB, regardless of the value size. Also, all compacted values stored in the Titan blob file are automatically moved back to RocksDB.
 
-To fully disable Titan for all existing and future data, you can follow these steps. Note that in general you can skip Step 2 because it can greatly impact online traffic performance. In fact even without Step 2, the data convertion consumes extra I/O and CPU resources, and performance will degrade (sometimes as much as 50%) when TiKV's I/O or CPU resources are limited.  
+To fully disable Titan for all existing and future data, you can follow these steps. Note that in general you can skip Step 2 because it can greatly impact online traffic performance. In fact even without Step 2, the data compaction consumes extra I/O and CPU resources when it migrates data from Titan to RocksDB, and performance will degrade (sometimes as much as 50%) when TiKV's I/O or CPU resources are limited.  
 
 1. Update the configuration of the TiKV nodes you wish to disable Titan for. You can update configuration in two methods:
 
@@ -144,9 +144,9 @@ To fully disable Titan for all existing and future data, you can follow these st
 
     > **Note:**
     >
-    > Use the default value `0.5` for [`discardable-ratio`](/tikv-configuration-file.md#discardable-ratio) when there is not enough disk space to hold both Titan and RocksDB data. In general, it is recommended to use the default value if the free disk space is less than 50%. This is because when `discardable-ratio = 1.0`, the RocksDB data keeps growing. At the same time, the recovery of Titan's original blob file requires all the data in that file to be migrated to RocksDB, which is a slow process. If the disk size is big enough, setting `discardable-ratio = 1.0` can reduce the GC of the blob file itself during compaction, which saves bandwidth.
+    > When there is insufficient disk space to accommodate both Titan and RocksDB data, it is recommended to use the default value of `0.5` for [`discardable-ratio`](/tikv-configuration-file.md#discardable-ratio). In general, if the free disk space is below 50%, it is advisable to use the default value. This is because when `discardable-ratio = 1.0`, the RocksDB data keeps growing. At the same time, the recovery of Titan's original blob file requires all the data in that file to be migrated to RocksDB, which is a slow process. However, if the disk size is large enough, setting `discardable-ratio = 1.0` can reduce the GC of the blob file itself during compaction, which saves bandwidth.
 
-2. [Optional] Perform a full compaction using tikv-ctl. This process will consume a large amount of I/O and CPU resources.
+2. (Optional) Perform a full compaction using tikv-ctl. This process will consume a large amount of I/O and CPU resources.
 
     ```bash
     tikv-ctl --pd <PD_ADDR> compact-cluster --bottommost force

diff --git a/storage-engine/titan-overview.md b/storage-engine/titan-overview.md
@@ -31,7 +31,7 @@ The prerequisites for enabling Titan are as follows:
 - No range query will be performed or you do not need a high performance of range query. Because the data stored in Titan is not well-ordered, its performance of range query is poorer than that of RocksDB, especially for the query of a large range. According PingCAP's internal test, Titan's range query performance is 40% to a few times lower than that of RocksDB.
 - Sufficient disk space (consider reserving a space twice of the RocksDB disk consumption with the same data volume). This is because Titan reduces write amplification at the cost of disk space. In addition, Titan compresses values one by one, and its compression rate is lower than that of RocksDB. RocksDB compresses blocks one by one. Therefore, Titan consumes more storage space than RocksDB, which is expected and normal. In some situations, Titan's storage consumption can be twice that of RocksDB.
 
-Starting from v7.6.0, Titan is improved and is enabled by default for newly created clusters. Because small KV datasets will still be stored in RocksDB even Titan is enabled, you can still enable Titan in the configuration. 
+Starting from v7.6.0, Titan is improved and is enabled by default for newly created clusters. Because small KV datasets will still be stored in RocksDB even when Titan is enabled, you can still enable Titan in the configuration. 
 
 If you want to improve the performance of Titan, see the blog post [Titan: A RocksDB Plugin to Reduce Write Amplification](https://pingcap.com/blog/titan-storage-engine-design-and-implementation/).