diff --git a/Optimization.md b/Optimization.md
index a9d6cdb..9c6d49a 100644
--- a/Optimization.md
+++ b/Optimization.md
@@ -69,6 +69,8 @@ By default, the volume server uses in memory index to achieve O(1) disk read. Ro
 
 Another aspect is the total file size that are read at the same time. If serving 100KB-sized file for 1000 concurrent reads, 100MB memory is needed. 
 
+For large files uploaded through filer, auto-chunking would be applied, the default value is `weed filer -maxMB=32`. So if your system is going to support 1000 concurrent reads, `1000 x 32MB` memory is needed.
+
 ## Insert with your own keys
 
 The file id generation is actually pretty trivial and you could use your own way to generate the file keys.