how to move to dir.idx

Tiered-Storage.md

@@ -15,6 +15,8 @@ To write any data, the volume index needs to append one entry. To read any data,
 
 You can run `weed volume -dir.idx=/fast/disk/dir` or `weed server -volume.dir.idx=/vast/disk/dir` to ensure the volume index is located on a fast disk, e.g., a fast SSD mount.
 
+If the volume server already has some existing data, you can just stop the volume server, move the `.idx` files to the index folder, and restart the volume server.
+
 # SSD & HDD Volume Disk Types
 
 If the volume data also needs fast access, you can create them on fast disks.
@@ -64,4 +66,3 @@ volume.move -source <source volume server host:port> -target <target volume serv
 
 ### Manually move volume files
 For now, if you only want to change the disk type of a volume, and the volume server is not running, you can simply move the volume data from ssd directory to hdd directory, or vice versa.
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