support multiple sample file directories

This is still pretty basic support. There's no config UI support for
renaming/moving the sample file directories after they are created, and no
error checking that the files are still in the expected place. I can imagine
sysadmins getting into trouble trying to change things. I hope to address at
least some of that in a follow-up change to introduce a versioning/locking
scheme that ensures databases and sample file dirs match in some way.

A bonus change that kinda got pulled along for the ride: a dialog pops up in
the config UI while a stream is being tested. The experience was pretty bad
before; there was no indication the button worked at all until it was done,
sometimes many seconds later.

guide/install.md

@@ -99,9 +99,9 @@ state:
 
    * a SQLite database, typically <1 GiB. It should be stored on flash if
      available.
-   * the "sample file directory", which holds the actual samples/frames of
-     H.264 video. This should be quite large and typically is stored on a hard
-     drive.
+   * the "sample file directories", which hold the actual samples/frames of
+     H.264 video. These should be quite large and are typically stored on hard
+     drives.
 
 (See [schema.md](schema.md) for more information.)
 
@@ -134,23 +134,27 @@ You can configure the system through a text-based user interface:
 
     $ sudo -u moonfire-nvr moonfire-nvr config 2>debug-log
 
-In the user interface, add your cameras under the "Edit cameras" dialog.
-There's a "Test" button to verify your settings directly from the dialog.
+In the user interface,
 
-After the cameras look correct, go to "Edit retention" to assign disk space to
-each camera. Leave a little slack (at least 100 MB per camera) between the total
-limit and the filesystem capacity, even if you store nothing else on the disk.
-There are several reasons this is needed:
+ 1. add your sample file dirs under "Edit cameras and retention"
+ 2. add cameras under the "Edit cameras and streams" dialog.
+    There's a "Test" button to verify your settings directly from the dialog.
+    Be sure to assign each stream you want to capture to a sample file
+    directory.
+ 3. Assign disk space to your cameras back in "Edit cameras and retention".
+    Leave a little slack (at least 100 MB per camera) between the total limit
+    and the filesystem capacity, even if you store nothing else on the disk.
+    There are several reasons this is needed:
 
-   * The limit currently controls fully-written files only. There will be up
-     to two minutes of video per camera of additional video.
-   * The rotation happens after the limit is exceeded, not proactively.
-   * Moonfire NVR currently doesn't account for the unused space in the final
-     filesystem block at the end of each file.
-   * Moonfire NVR doesn't account for the space used for directory listings.
-   * If a file is open when it is deleted (such as if a HTTP client is
-     downloading it), it stays around until the file is closed. Moonfire NVR
-     currently doesn't account for this.
+       * The limit currently controls fully-written files only. There will be up
+         to two minutes of video per camera of additional video.
+       * The rotation happens after the limit is exceeded, not proactively.
+       * Moonfire NVR currently doesn't account for the unused space in the final
+         filesystem block at the end of each file.
+       * Moonfire NVR doesn't account for the space used for directory listings.
+       * If a file is open when it is deleted (such as if a HTTP client is
+         downloading it), it stays around until the file is closed. Moonfire NVR
+         currently doesn't account for this.
 
 When finished, start the daemon:
 
@@ -168,7 +172,6 @@ been done for you. If not, Create
 
     [Service]
     ExecStart=/usr/local/bin/moonfire-nvr run \
-        --sample-file-dir=/var/lib/moonfire-nvr/sample \
         --db-dir=/var/lib/moonfire-nvr/db \
         --http-addr=0.0.0.0:8080
     Environment=TZ=:/etc/localtime

guide/schema.md

@@ -197,6 +197,8 @@ The general upgrade procedure applies to this upgrade.
 Version 2 adds:
 
 *   recording of sub streams (splits a new `stream` table out of `camera`)
+*   support for multiple sample file directories, to take advantage of
+    multiple hard drives (or multiple RAID volumes).
 *   records the RFC-6381 codec associated with a video sample entry, so that
     logic for determining this is no longer needed as part of the database
     layer.