Better header and detail why you need two times the storage. Also moving memory…

doc/install/requirements.md

-# Memory
-
-We recommend you to run GitLab on a server with at least 1GB of RAM memory. You can use it with 512MB of memory but you need to setup unicorn to use only 1 worker and you need at least 200MB of swap. On a server with 1.5GB of memory you are able to support 1000+ users.
-
-
-# Hard disk capacity
-
-The necessary hard disk space largely depends on the size of the repos you want
-to store in GitLab. But as a *rule of thumb* you should have at least twice as much
-free space as your all repos combined take up. Apart from a local hard drive you can also mount a volume that supports the network file system (NFS) protocol. This volume might be located on a file server, a network attached storage (NAS) device, a storage area network (SAN) or on an Amazon Web Services (AWS) Elastic Block Store (EBS) volume.
-
-
 # Operating Systems
 
 ## Linux
@@ -41,7 +29,6 @@ GitLab does **not** run on Windows and we have no plans of supporting it in the
 near future. Please consider using a virtual machine to run GitLab.
 
 
-
 # Rubies
 
 GitLab requires Ruby (MRI) 1.9.3 and several Gems with native components.
@@ -50,6 +37,17 @@ While it is generally possible to use other Rubies (like
 some work on your part.
 
 
+# Memory
+
+We recommend you to run GitLab on a server with at least 1GB of RAM memory. You can use it with 512MB of memory but you need to setup unicorn to use only 1 worker and you need at least 200MB of swap. On a server with 1.5GB of memory you are able to support 1000+ users.
+
+
+# Storage
+
+The necessary hard disk space largely depends on the size of the repos you want
+to store in GitLab. But as a *rule of thumb* you should have at least twice as much
+free space as your all repos combined take up. You need twice the storage because [GitLab satellites](https://github.com/gitlabhq/gitlabhq/blob/master/doc/install/structure.md) contain an extra copy of each repo. Apart from a local hard drive you can also mount a volume that supports the network file system (NFS) protocol. This volume might be located on a file server, a network attached storage (NAS) device, a storage area network (SAN) or on an Amazon Web Services (AWS) Elastic Block Store (EBS) volume.
+
 
 # Installation troubles and reporting success or failure