* It is easy for existing tools to access files in Keep.
* Data is downloaded on demand. It is not necessary to download an entire file or collection to start processing.
-The default mode permits browsing any collection in Arvados as a subdirectory under the mount directory. To avoid having to fetch a potentially large list of all collections, collection directories only come into existence when explicitly accessed by their keep locator.
+The default mode permits browsing any collection in Arvados as a subdirectory under the mount directory. To avoid having to fetch a potentially large list of all collections, collection directories only come into existence when explicitly accessed by their Keep locator. For instance, a collection may be found by its content hash in the @keep/by_id@ directory.
<notextile>
<pre><code>~$ <span class="userinput">mkdir -p keep</span>
~$ <span class="userinput">arv-mount keep</span>
-~$ <span class="userinput">cd keep/c1bad4b39ca5a924e481008009d94e32+210</span>
-~/keep/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">ls</span>
+~$ <span class="userinput">cd keep/by_id/c1bad4b39ca5a924e481008009d94e32+210</span>
+~/keep/by_id/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">ls</span>
var-GS000016015-ASM.tsv.bz2
-~/keep/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">md5sum var-GS000016015-ASM.tsv.bz2</span>
+~/keep/by_id/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">md5sum var-GS000016015-ASM.tsv.bz2</span>
44b8ae3fde7a8a88d2f7ebd237625b4f var-GS000016015-ASM.tsv.bz2
-~/keep/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">cd ../..</span>
+~/keep/by_id/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">cd ../..</span>
~$ <span class="userinput">fusermount -u keep</span>
</code></pre>
</notextile>
+
+The last line unmounts Keep. Subdirectories will no longer be accessible.
+
+Within each directory on Keep, there is a @.arvados#collection@ file that does not show up with @ls@. Its contents include, for instance, the @portable_data_hash@, which is the same as the Keep locator.