From 7eda47a9b35b387f3b2497633c586cdb4eae4d4e Mon Sep 17 00:00:00 2001
From: Olivier Lambert <olivier.lambert@vates.fr>
Date: Fri, 18 Aug 2017 19:26:58 +0200
Subject: [PATCH] feat(xosan): add disperse type

---
 docs/xosan_disperse.md | 46 ++++++++++++++++++++++++++++++++++++++++++
 docs/xosan_types.md    |  2 +-
 2 files changed, 47 insertions(+), 1 deletion(-)
 create mode 100644 docs/xosan_disperse.md

diff --git a/docs/xosan_disperse.md b/docs/xosan_disperse.md
new file mode 100644
index 000000000..70a476655
--- /dev/null
+++ b/docs/xosan_disperse.md
@@ -0,0 +1,46 @@
+## Disperse type
+
+Data are chunked and dispered on multiple nodes. There is a kind of "parity" data allowing to lost one or mode nodes ("like" RAID 5 or RAID 6).
+
+Pros:
+
+* good capacity (perfect for **HDD storage**)
+* simple to setup
+* simple to maintain
+* various level of protection
+
+Cons:
+
+* not all configrations possible (3, 5, 6 nodes and more)
+* limited performances on SSDs (replication is better in this case)
+
+![pictore disperse principle]()
+
+### Disperse 3
+
+This is similar to **RAID 5**: there is an [algorithm](https://en.wikipedia.org/wiki/Reed%E2%80%93Solomon_error_correction) that will generate a kind of parity, being able to continue to work even if 1 node is down. If you reintroduce the node, it will be "healed" automatically.
+
+![picture disperse 3]()
+
+If you lose one node, your data are still here. This mode will give you **66% of your total disk space**.
+
+### Disperse 5
+
+Same than 3, like **RAID 5**, you can lose 1 node without service interruption.
+
+![picture disperse 5]()
+
+In this case, you'll be able to use up to **80%** of your total storage capacity!
+
+### Disperse 6
+
+It's very similar to **RAID 6**. You can lose up to 2 nodes, it will continue to work in read and write.
+
+![picture disperse 6]()
+
+## Growing a disperse XOSAN
+
+You can grow a replicated XOSAN by adding extra disperse volumes, in other words a new disperse will be like in RAID 0 with the old one. It's a distributed-disperse type. Some examples:
+
+* To grow a disperse 3, you need 3 new nodes. You'll add the total capacity of each disperse to make a distributed-disperse on 2x3 dispersed nodes.
+* To grow a disperse 6, you need 6 new nodes.
diff --git a/docs/xosan_types.md b/docs/xosan_types.md
index c550ebe70..5d645c0ab 100644
--- a/docs/xosan_types.md
+++ b/docs/xosan_types.md
@@ -9,4 +9,4 @@ That's why it's **very important to understand pros and cons** of each type.
 Here is those 2 types:
 
 * [Replicated](xosan_replicated.md)
-* [Disperse](xosan_replicated.md)
+* [Disperse](xosan_disperse.md)