The MP3/AAC files are generated by the Core and take up disk space. If you don't use this function, disable it. I believe it also saves some "scratch space" for whatever reason. All I know is, when I filled up my MC200 I couldn't delete anything. Luckily my backups were good and I bought a TwinStore, oddly when I restored my albums to the TwinStore, the deleted albums were there again. I deleted and re-imported them just in case.

I disabled the storage using the windows utility and it wiped the music on the MC200.

-Mike

Primary: 818v3+ID41, M6 stereo pair, M SpeakerLink cabling, Sonos+96kHz Cullen, silver DSW
HT: Marantz prepro, 271, DSP3300, 8K SE FL/FR pair, DSP M6x2, DSP320x4 (ceiling), black DSW, 520 RL/RR rear in-walls
Living Room: G65, 640 L/R in-walls, UHD722, MS600
Vac. Home: G61, HD621, 4xDSP3100, DSP3100HC
MDMS:NUC/ROCK+TrueNAS Core 12.0 ZFS file server