[Matthijs]

When creating thumbnails and extracting metadata, the system really has to open and render each document. It cannot at present do that in the background without interfering with already open documents, but that would be a future improvement.

The indexing has two steps:
1) Find all files and folders on the card and sync that structure with global.db
2) For each newly added file, open it and get thumbnail & metadata

The first one should be pretty quick and depends only on the number of files and folders on your card. It runs each time the SD card is mounted.

The second one depends not only on number of files, but also on the complexity of your documents. You can disable (2) using the Advanced Settings. We're thinking about disabling this by default for DR1000S.