Updated Large File Handling (markdown)

Large-File-Handling.md

@@ -1,17 +1,14 @@
 In order to achieve high concurrency, SeaweedFS tries to read and write the whole file into memory. But this would not work for large files. 
 
+The following is implemented in "weed upload" command. For 3rd party clients, here is the spec.
+
 To support large files, SeaweedFS supports these two kinds of files:
-* Chunk data File
+* Chunk File. Each chunk file is actually just normal files to SeaweedFS.
-* Chunk Manifest
+* Chunk Manifest. A simple json file with the list of all the chunks. 
 
-## Create new large file
+This piece of code shows the json file structure:
-
-SeaweedFS delegates the effort to the client side. The steps are:
-
-1. split large files into chunks
-1. upload each file chunks as usual, with mime type "application/octet-stream". Save the related info into ChunkInfo struct.
-1. upload the manifest file with mime type "application/json", and add url parameter "cm=true".
 
+https://github.com/chrislusf/seaweedfs/blob/master/go/operation/chunked_file.go#L24
 
 ```
 type ChunkInfo struct {
@@ -30,6 +27,17 @@ type ChunkManifest struct {
 }
 ```
 
+When reading Chunk Manifest files, the SeaweedFS will find and send the data file based on the list of ChunkInfo.
+
+## Create new large file
+
+SeaweedFS delegates the effort to the client side. The steps are:
+
+1. split large files into chunks
+1. upload each file chunks as usual, with mime type "application/octet-stream". Save the related info into ChunkInfo struct.
+1. upload the manifest file with mime type "application/json", and add url parameter "cm=true".
+
+
 ## Update large file
 
 Usually we just append large files. Updating a specific chunk of file is almost the same.