Merge pull request #145 from scottyhq/patch-1

Update Hub User Guide storage docs

user/storage.md

@@ -13,29 +13,45 @@ The following material was adapted from the
 [Pangeo Cloud User Guide](https://pangeo.io/cloud.html)
 :::
 
-## Your Home Directory
+## The JupyterHub Filesystem
 
 Your notebook server is a linux "virtual machine" with its own filesystem.
-Your are not on a shared server; you are on your own private server.
-Your username is ``jovyan``, and your home directory is ``/home/jovyan``.
-This is the same for all users.
-
-Your home directory is intended only for notebooks, analysis scripts, and small datasets (< 1 GB).
-It is not an appropriate place to store large datasets.
-No one else can see or access the files your home directory.
+You are not on a shared server; you are on your own private server.
 
 The easiest way to move files in and out of your home directory is via the JupyterLab web interface.
 Drag a file into the file browser to upload, and right-click to download back out.
 You can also open a terminal via the JupyterLab launcher and use this to ssh / scp / ftp to remote systems.
 However, you can’t ssh in!
 
-## The `shared` Directory
+### Your Home Directory
+
+Your username is ``jovyan``, and your home directory is ``/home/jovyan``.
+This is the same for all users, but no one else can see or access the files in *your* home directory.
+
+``/home/jovyan`` is a persistant network-attached drive. Any files you put there will be there when you
+log out and log back into the JupyterHub. 
+
+The ``/home/jovyan`` space is typically limited to 10 GB. Consequently, your home directory is intended 
+only for notebooks, analysis scripts, and small datasets (< 1 GB). It is not an appropriate place to store 
+large datasets.
+
+### The `shared` Directory
 
 All users have a directory called `shared` in their home directory.
 This is a *readonly* directory - anybody on the hub can *access* and *read from* the `shared` directory.
 The hub administrator may choose to distribute shared materials via this directory.
 The `shared` directory is not intended as a way for hub users to share data with each other.
 
+### The `/tmp` Directory
+
+Any directory outside of ``/home/jovyan`` is emphemeral on Cloud-hosted JupyterHubs. This means if you 
+add data or scripts under a writeable directory like `/tmp/myfile.txt` *it will not be there when you
+log out and log back in*. 
+
+Nevertheless, `/tmp` is a convenient location for storing data temporarily 
+because it is a fast SSD drive. The space available depends on your server but will generally be much 
+larger than ``/home/jovyan`` (50-100s of GB).
+
 ## Using Git / GitHub
 
 The recommended way to move code in and out of the hub is via git / GitHub.