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SidecarEXPANDER

Storage

The Sidecar boots from its SD card, which stays the place of record: projects, pools and samples live there. Besides it, it mounts USB drives as they are plugged in and, on the Pi 5, an NVMe SSD. In 0.3.0 a USB stick is used for:

  • recordings: record straight to the stick (Recording to a USB drive);
  • bundles: import a bundle from the stick. Export to a stick is off in 0.3.0: export to the card, then copy the bundle (USB sticks);
  • the storage bench.

Samples stay on the SD card for now: the machines play samples from the card only. in testing

Drive Name Board
SD card SD Pi 4B, Pi 5
USB drives (up to three) USB, USB2, USB3 Pi 4B, Pi 5
NVMe SSD on the PCIe connector NVME Pi 5

Saves are instant, and safe in a power cut

Section titled “Saves are instant, and safe in a power cut”

hardware (2026-10-26: no clicks on kit and pattern changes, a power cut after an edit kept everything). When a project loads, the Sidecar reads its small files (the poly patterns, the LFOs, the insert settings, the pool lists) into RAM. While you play:

  • A kit or pattern change reads from RAM, never from the card, so it cannot cause a dropout. The sample browser lists folders from a RAM index too.
  • An edit changes RAM at once and reaches the card a moment later, as a whole file (written beside the old one, then swapped in).
  • A power cut keeps the previous whole file. At worst the very last edit, not yet written, is lost; a file is never half written, and the next boot finishes any swap that was cut in the middle.
  • For a few seconds after the Rytm switches project, while the files load, edits to it are refused with a “loading” message instead of being lost.

Formatting a USB drive

Section titled “Formatting a USB drive”

FAT32 with the MBR scheme (“Master Boot Record”):

  • Mac: Disk Utility, View > Show All Devices, select the device (not the volume), Erase, Format MS-DOS (FAT), Scheme Master Boot Record.
  • Windows: sticks come with MBR. Pick FAT32; Windows’ own dialog offers it only up to 32 GB, so use a FAT32 tool for larger drives.

Not mounted in this build:

  • GPT (Disk Utility’s default “GUID Partition Map”);
  • exFAT (the default of macOS and Windows for large drives).

The log and the web page say which it is: “GPT partition table: use the MBR scheme (FAT32)”, “exFAT: FAT32 only in this build”. FAT32 limits a file to 4 GB, which is fine for samples and bundles. Drives with 4 KB logical sectors are refused.

USB drives

Section titled “USB drives”
  • Plug it in: a blue USB 3 port on the Pi 4 (the Rytm sits on a black USB 2 port), any port on the Pi 5. It mounts within a second. It shows on the touchscreen’s STATUS page (UP + T10) under LINKS (USB DRIVE) and on the web page’s Status tab under Storage.
  • Eject before pulling it: the web page’s Eject, the PROJECT page’s EJECT, or stor=eject:USB on the console. It then says “ejected: safe to remove”. A drive pulled while mounted is unmounted at once; a write in progress can be lost (FAT32 has no journal).
  • An ejected drive left plugged in: stor=rescan (Pi 4) brings it back; on the Pi 5 unplug and plug it.
  • A drive that did not mount (wrong format) and was re-formatted: plug it in again, or stor=mount:USB.
  • Some sticks need usbpowerdelay=1500 in cmdline.txt to be found.

NVMe SSD (Pi 5)

Section titled “NVMe SSD (Pi 5)”
  • An M.2 HAT on the Pi 5’s PCIe connector (the official M.2 HAT+ or a bottom-mount NVMe base).
  • Format it FAT32 with the MBR scheme, as above (on Windows a 256 GB+ SSD needs a FAT32 tool). 512-byte sectors only.
  • The NVMe driver is experimental. Use an SSD with nothing on it you cannot lose; the SD card stays the boot drive and the place of record.
  • It is looked for once at boot (no hot-plug), and from 0.4.0 only with nvme=1 in cmdline.txt: the search could drop a Rytm that was already attached. Before 0.4.0 it was on by default and nvme=0 skipped it.
  • stor=eject:NVME unmounts it; it stays listed as ejected until the next boot (stor=mount:NVME mounts it again).

Measuring a drive: stor=bench

Section titled “Measuring a drive: stor=bench”

The storage bench measures a drive’s sequential and random speed, and how much it disturbs the Sidecar while the audio runs. It never runs by itself and never formats anything: it writes two test files and removes them.

Start it with the Rytm connected but stopped and nothing recording, from the web page’s Status tab (Storage, Run bench) or the console (the web page’s Log & console, or the serial console with a : before each line):

stor                 # the drives: state, format, free space, link
stor=bench:SD        # the SD card (a few minutes; the sound may drop out)
stor=bench:USB       # a USB stick or SSD
stor=bench:NVME      # Pi 5: the NVMe SSD
stor=last            # the last result again
stor=cancel          # stop it, remove its files
  • Options: stor=bench:USB:512 sets the test file’s size in MB (default 256), n= the number of random reads.
  • Refused while the Rytm plays, a take plays back, the recorder is armed or records, or the drive is not mounted.
  • The result is a table in the log and on the web page, also saved as /.rytm/storbench-<drive>.txt on the SD card.
  • The streaming budget uses the bench’s numbers: how many sample streams a drive can carry.

What to expect (estimates, to be measured on the Pi): SD card 15-22 MB/s read, 8-12 MB/s write; USB 2 stick 20-35 MB/s; USB 3 stick or SSD 80-250 MB/s; NVMe about 280 MB/s reads.

Folders on the SD card

Section titled “Folders on the SD card”

The web page’s Files tab reaches the card’s content folders (and nothing else, since 0.3.0). The ones you fill yourself:

Folder What goes in
/Samples WAV and AIFF samples for the pools and the machines
/MULTISAMPLE .sfz instruments for MULTISAMPLE
/WAVETABLES wavetables for WAVETABLE
/NAM amp captures (.nam, .namb, A2-Lite) for the insert effect AMP. Make the folder if it is not there; amp=rescan on the console reads it again
/Plugins user machines (.a64.rmp)
/JUNO, /DX7 JUNO and 6-OP FM patches
/Bundles project bundles
/Recordings the recorder’s takes

The Sidecar’s own folder /.rytm (settings, project files, the trash) is not reachable from the web page: use a card reader.

Limitations

Section titled “Limitations”
  • Sidecar (Pi) only. The drives are not yet measured on a Pi.
  • FAT32 with MBR only: exFAT and GPT are a build option that is off (tested on the Mac only).
  • In 0.3.0 the extra drives hold recordings and bundles to import; projects, pools and samples play from the SD card. The sample library does not index USB drives.
  • NVMe is experimental (one queue, no power management): test SSDs only.
  • A drive pulled without eject can lose a write in progress.