Update README.md, add example

Author: rokups

README.md

@@ -3,8 +3,9 @@ zinc - the reverse-rsync
 
 [![Build Status](https://travis-ci.org/rokups/zinc.svg?branch=master)](https://travis-ci.org/rokups/zinc)
 
-**WARNING:** This code is very immature, likely buggy and a subject to change. It would be great if it saw some testing
-from people other than me, however if you use it for anything serious and it breaks - you get to keep both pieces.
+**WARNING:** **DO NOT USE IT WITH IMPORTANT AND/OR NOT BACKED UP DATA**. This code is of beta quality. I am fairly 
+certain it will not corrupt your data. Code was fuzz-tested for weeks without failures and is in use in a live 
+environment with rather small (few hundred) users without issues. However, you never know.
 
 rsync has become a synonym to efficient data synchronization. There are few issues however: server does heavy lifting
 and GPL license.
@@ -56,6 +57,34 @@ As you can see from diagram above process of synchronizing data is composed of t
 2. Delta calculation: Client obtains the list of block hashes, then calculates a rolling checksum on the local file. Using rolling checksum and list of remote file hashes algorithm determines what file parts need to be kept/copied/downloaded. Local file data will be reused as much as possible.
 3. Patching: Using a calculated delta map blocks in local file are rearranged much like a puzzle pieces, missing pieces are downloaded.
 
+### Example
+
+Project comes with a testing tool `zinc` which is used mainly for debugging. Tool is reading and writing local files.
+Example below was performed in tmpfs, ISO files were about 500MB and tested CPU was i7-6800K (6 core / 12 thread). Due 
+to tmpfs you may consider test timing results as benchmark of core algorithm as file reading/writing basically happened 
+in memory.
+```sh
+/tmp % # Test files are rather old Archliux ISOs
+/tmp % sha1sum archlinux-2017.0*.iso
+77508eaf2be9f15e22b1cc920db12d4e90c2cf77  archlinux-2017.06.01-x86_64.iso
+dd03d811211c332d29155069d8e4bb2306c70f33  archlinux-2017.07.01-x86_64.iso
+
+/tmp % # Hash new ISO file. Produced json file is hosted on a remote (web)server along with the ISO
+/tmp % ./zinc --hash ./archlinux-2017.07.01-x86_64.iso ./archlinux-2017.07.01-x86_64.iso.json
+
+/tmp % # Client system obtains json file with hashes from a remote server and finds different and matching blocks
+/tmp % # Client system then moves existing matching blocks to their new locations while downloading missing blocks from remote server
+/tmp % time ./zinc ./archlinux-2017.07.01-x86_64.iso ./archlinux-2017.06.01-x86_64.iso
+Calculating delta : [##################################################] 100.00
+Patching file     : [##################################################] 100.00
+./zinc ./archlinux-2017.07.01-x86_64.iso   70.23s user 0.24s system 977% cpu 7.206 total
+
+/tmp % # ISO was updated in less than a second
+/tmp % sha1sum archlinux-2017.0*.iso
+dd03d811211c332d29155069d8e4bb2306c70f33  archlinux-2017.06.01-x86_64.iso
+dd03d811211c332d29155069d8e4bb2306c70f33  archlinux-2017.07.01-x86_64.iso
+```
+
 ### Other similar software
 * [rsync](https://rsync.samba.org/) - inspiration of zinc
 * [zsync](http://zsync.moria.org.uk/) - inspiration of zinc