docs: fix TiKV RocksDB block-size defaults (#23269) (#23271)

Author: ti-chi-bot

storage-engine/rocksdb-overview.md

@@ -27,7 +27,7 @@ As the storage engine of TiKV, RocksDB is used to store Raft logs and user data.
 
 ## RocksDB memory usage
 
-To improve the reading performance and reduce the reading operations to the disk, RocksDB divides the files stored on the disk into blocks based on a certain size (the default is 64 KB). When reading a block, it first checks if the data already exists in BlockCache in memory. If true, it can read the data directly from memory without accessing the disk.
+To improve the reading performance and reduce the reading operations to the disk, RocksDB divides the files stored on the disk into blocks based on a certain size (the default is 32 KiB). When reading a block, it first checks if the data already exists in BlockCache in memory. If true, it can read the data directly from memory without accessing the disk.
 
 BlockCache discards the least recently used data according to the LRU algorithm. By default, TiKV devotes 45% of the system memory to BlockCache. Users can also modify the `storage.block-cache.capacity` configuration to an appropriate value by themselves. However, it is not recommended to exceed 60% of the total system memory.
 

tune-tikv-memory-performance.md

@@ -145,7 +145,7 @@ max-manifest-file-size = "20MiB"
 [rocksdb.defaultcf]
 # The data block size. RocksDB compresses data based on the unit of block.
 # Similar to page in other databases, block is the smallest unit cached in block-cache.
-block-size = "64KB"
+block-size = "32KiB"
 
 # The compaction mode of each layer of RocksDB data. The optional values include no, snappy, zlib,
 # bzip2, lz4, lz4hc, and zstd. Note that the Snappy compressed file must be in the [official Snappy format](https://github.com/google/snappy). Other variants of Snappy compression are not supported.