The main bottleneck during a scan is disk I/O (see' this post'
...
> Memory isn't really important (since the scan mostly writes to the
> database, making caching impossible)
I'm sorry to say that this is oversimplified. Many IO issues are
addressed by using more memory (caching, buffers). There are too many
variables you don't take into account:
- memory base line: are we talking about a NAS or old Pi with 512MB of
RAM or a PC with gigabytes of it
- are we talking about SSD vs. USB2 connected HD?
- I/O of what? Music file storage or DB cache location?
- scanner plugins doing remote lookups
- configuration of those plugins to use local caching or not
- memory/caching can make a huge difference on I/O
- number of playlists and playlist sizes (an important factor for the
FTS indexing)
- size of your online library (again with playlists of thousands of tracks)
Ok, you could say that doing online lookups (library or covers or
whatever) was I/O, too. But that's not what you meant.
The "maximum memory" option I introduced as the result of a lot of
scanner profiling. While you were right that it mostly addressed the IO
bottleneck, it did so by throwing more memory at the scanner. Memory
definitely makes a difference. If you look at the code you'll see that
there are a lot of tweaks which would configure the DB connection
differently in the scanner vs. server. More memory is being used in the
scanner to limit the writes, while in the server it's used to limit the
reads from disk.
Therefore I'd say you can't generalize this problem without looking at
the individual configuration.
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