My idea when buying the QNAP was to use it as a low-power alternative to keeping my workstation switched on all the time for access to my music collection from the Squeezebox.
Low power processors have a drawback, though - you don't get that much processing power out of them. Running Squeezecenter on it turned out to work.. but not very fast.
The QNAP TS-109 II has 256Mb of memory. That's good, because squeezecenter alone consumes about 70Mb of virtual memory, och which 60 is resident. The MySQL server started by squeezecenter will consume another 97M virtual/20Mb resident. Part of the virtual memory used by MySQL is probably mmap:ed files, and that doesn't really count.
With only squeezecenter and the standard set of daemons such as syslogd and dhcpd running, and NFS server in the kernel, it seems like there's not much swap usage, so the amount of available memory is not extremely low. Don't try the 128Mb version of the QNAP, though, that will be painstakingly slow because much more swap will be required.
Web Interface Performance
The web interface is rather slow. You have to wait several seconds before things appear, and it also seems like the CPU consumption increases significantly while using the web interface.
One strange thing is that the CPU consumption of the perl process is very high, while the CPU consumption of the MySQL process is very low. One has to wonder if the SQL database is used in an optimal way. Letting the database do most of the work is often the best way to achieve good performance. Doing a lot of processing after the data has been read from the database is a bad way. But, I have not studied the database operations in detail, this is just guesswork from my side.
Changing from the default skin to the Classic skin did help, but it's still slow.
Using the Squeezebox to search for music
Using the remote to search for music via the squeezebox has good performance. Starting playback sometimes has a slight delay, which I think in most cases is because of transcoding..
Transcoding Ogg Vorbis files
The firmware for the Squeezebox has support for decoding Ogg Vorbis files, but unfortunately it doesn't seem to work well at all. It can't read about half of my Ogg Vorbis files. Even newly ripped files are troublesome, and if I rip CD and code it into Ogg Vorbis, some of the files will work in the Squeezebox, some will not.
Since I do have a lot of Ogg Vorbis files, the solution is to have Squeezecenter transcode the Ogg data to another format that the Squeezebox understands, before sending it over the network. This process is called transcoding.
I first tried to transcode into FLAC, but that was too CPU-intensive for the QNAP TS-109 II to handle - probably because two compressed formats were involved.
Transcoding from Ogg to AIFF does seem to work rather well - there is still a slight delay before you can hear the music after pressing play on the remote.
An interesting experiment would be to use the integer-only Ogg decoder, Tremor. That might speed things up because as far as I understand, floating point performance is not that good on the ARM architecture.
Running Squeezecenter on the QNAP TS-109 II does work, but it's a bit slow. Part of the problem is that Squeezecenter is rather bloated, functionality-wise.
It's a pity the only documentation on the protocol used between squeezecenter and squeezebox is the Perl source code.