17. Storage Management

This document provides a systematic overview of storage classification and management on the ArmSoM board from a storage architecture perspective.

17.1 Storage System Overview

The ArmSoM board uses a tiered storage architecture consisting of four layers:

• Primary Storage (eMMC): System disk
• Expansion Storage (SD Card): Data/Backup disk
• High-Speed Storage (SSD): High-performance storage
• Removable Storage (USB Drive): Temporary data exchange

These appear as different types of block devices in Linux:

Storage Type	Device Node	Interface
eMMC	/dev/mmcblk0	Onboard
SD卡	/dev/mmcblk1	SD Card Slot
NVMe SSD	/dev/nvme0n1	M.2 PCIe
USB Drive	/dev/sda	USB Port

17.2 Storage Type Details

This section uses the ArmSoM Sige7 board as an example.

17.2.1 eMMC Storage

eMMC is the default system storage medium on the Sige7 and is soldered directly onto the board.

Default Configuration & Specifications:

1. Capacity Options: 32GB / 64GB / 128GB

2. Interface Standard: eMMC 5.1

3. Typical Speed: Read ~300MB/s, Write ~150MB/s

4. Device Node: /dev/mmcblk0

eMMC Partition Layout:

# Typical eMMC partition layout
/dev/mmcblk0       # eMMC main device
├─/dev/mmcblk0p1   # Boot partition (U-Boot)
├─/dev/mmcblk0p2   # System partition (rootfs)
├─/dev/mmcblk0p3   # Data partition
├─/dev/mmcblk0boot0 # Bootloader partition 1 (4MB)
└─/dev/mmcblk0boot1 # Bootloader partition 2 (4MB)

17.2.2 MicroSD Card Storage

The Sige7 features an onboard MicroSD card slot. Theoretically, it supports cards up to 2TB. Like eMMC, it is driven by the MMC subsystem and appears as /dev/mmcblk1.

Use Cases for SD Cards:

1. Booting the system (priority is higher than eMMC)

2. Data backup and expansion

3. Multi-system booting and testing

17.2.3 NVMe SSD Storage

The Sige7 provides an M.2 Key M interface that supports NVMe protocol SSDs.

1. Interface Type: M.2 Key M

2. PCIe Specification: PCIe 3.0 x4

3. Theoretical Speed: ~3.5 GB/s

4. Device Node: /dev/nvme0n1

NVMe SSD Partition Example:

/dev/nvme0n1       # NVMe main device
├─/dev/nvme0n1p1   # First partition
└─/dev/nvme0n1p2   # Second partition

17.2.4 USB Drive Storage

The Sige7 provides USB ports (1x USB 3.0, 1x USB 2.0, 1x USB Type-C) and supports various USB drives and external hard drives.

USB Drive Device Nodes:

/dev/sda            # First USB storage device
├─/dev/sda1         # First partition
├─/dev/sda2         # Second partition

/dev/sdb            # Second USB storage device
└─/dev/sdb1

17.3 Identifying and Viewing Storage Devices

List all storage devices in a tree structure:

lsblk

# Example output on Sige7:
# mmcblk0        179:0    0  58.3G  0 disk
# ├─mmcblk0p1    179:1    0    16M  0 part  /boot
# ├─mmcblk0p2    179:2    0   128M  0 part
# └─mmcblk0p3    179:3    0  58.1G  0 part  /
# mmcblk1        179:8    0  29.7G  0 disk
# └─mmcblk1p1    179:9    0  29.7G  0 part  /mnt/sd
# nvme0n1        259:0    0   512G  0 disk
# └─nvme0n1p1    259:1    0   512G  0 part  /mnt/ssd
# sda              8:0    0  57.6G  0 disk
# └─sda1           8:1    0  57.6G  0 part  /mnt/usb

View detailed disk information:

# View partition details for all disks
sudo fdisk -l

# View details for a specific device
sudo fdisk -l /dev/mmcblk0
sudo fdisk -l /dev/nvme0n1
sudo fdisk -l /dev/sda

17.4 Partitioning and Formatting Storage Devices

17.4.1 Check Device Status

Check if a device already has partitions:

lsblk /dev/mmcblk1

If the output shows only mmcblk1 without an mmcblk1p1 entry, the device is not partitioned.

17.4.2 Creating a Partition

Example using an SD card (/dev/mmcblk1):

sudo fdisk /dev/mmcblk1

# Interactive fdisk commands:
# n - Create new partition
# p - Select primary partition type
# 1 - Partition number
# Enter - Accept default first sector
# Enter - Accept default last sector (use all space)
# w - Write changes and exit

17.4.3 Formatting a Partition

Format as ext4 (recommended for Linux):

sudo mkfs.ext4 /dev/mmcblk1p1

Format as FAT32 (for Windows compatibility):

sudo mkfs.vfat -F 32 /dev/mmcblk1p1

Format as NTFS (for Windows, large files):

sudo mkfs.ntfs -f /dev/mmcblk1p1

Format as exFAT (cross-platform, large files):

sudo mkfs.exfat /dev/mmcblk1p1

17.5 Automatic Mounting Configuration

17.5.1 Automatic Mounting with udev Rules

udev is the Linux device manager that dynamically manages device files. Rules files allow for automatic device handling and configuration.

Create a udev rules file:

sudo vi /etc/udev/rules.d/99-storage-auto-mount.rules

Add the following content:

# 1. Automount SD card to /mnt/sd
ACTION=="add", KERNEL=="mmcblk1p1", RUN+="/usr/bin/systemd-mount --no-block --options=sync,noatime $env{DEVNAME} /mnt/sd"
ACTION=="remove", KERNEL=="mmcblk1p1", RUN+="/bin/sh -c 'sync && sleep 0.5 && /usr/bin/systemd-umount /mnt/sd 2>/dev/null || true'"

# 2. Automount NVMe SSD to /mnt/ssd
ACTION=="add", KERNEL=="nvme0n1p1", RUN+="/usr/bin/systemd-mount --no-block --options=noatime $env{DEVNAME} /mnt/ssd"
ACTION=="remove", KERNEL=="nvme0n1p1", RUN+="/usr/bin/systemd-umount /mnt/ssd"

# 3. Automount USB drives (FAT32/exFAT/NTFS) to /mnt/usb
ACTION=="add", KERNEL=="sd[a-z][0-9]", SUBSYSTEM=="block", RUN+="/usr/bin/systemd-mount --no-block --options=uid=1000,gid=1000,iocharset=utf8 $env{DEVNAME} /mnt/usb"
ACTION=="remove", KERNEL=="sd[a-z][0-9]", SUBSYSTEM=="block", RUN+="/usr/bin/systemd-umount /mnt/usb"

Create mount points and set permissions:

# Create mount directories
sudo mkdir -p /mnt/sd /mnt/ssd /mnt/usb

# Allow read/write for standard users
sudo chmod 777 /mnt/sd /mnt/ssd /mnt/usb

Reload udev rules:

sudo udevadm control --reload-rules
sudo udevadm trigger

17.5.2 Fixed Mounting with /etc/fstab

This method is suitable for scenarios requiring fixed mount points (e.g., system disks, data disks).

1. Get the device UUID:

sudo blkid

2. Edit the fstab file:

root@armsom:/# sudo cat /etc/fstab
# NVMe SSD (Data Disk) - Using UUID
UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx  /mnt/ssd  ext4  defaults,noatime  0  2

# SD Card (Backup Disk) - Using device path
/dev/mmcblk1p1  /mnt/sd  ext4  defaults,noatime  0  2

# USB Drive - Using UUID (FAT32 format)
UUID=XXXX-XXXX  /mnt/usb  vfat  defaults,uid=1000,gid=1000,umask=000,utf8  0  2

3. Test the mount configuration:

# Create mount points
sudo mkdir -p /mnt/ssd /mnt/sd /mnt/usb

# Test all mount points
sudo mount -a

# Check mount status
df -h

17.6 Common Storage Management Commands

Here is a summary of commonly used disk management commands:

# View all storage devices
lsblk

# View detailed disk partition information
sudo fdisk -l

# View filesystem mount status
df -h

# View device UUIDs
sudo blkid

# View eMMC information
mmc-utils mmc extcsd read /dev/mmcblk0 2>/dev/null

# View NVMe SSD information
sudo nvme list

# View USB devices
lsusb

# Test disk read speed
sudo hdparm -t /dev/mmcblk0
sudo hdparm -t /dev/nvme0n1

# Test disk write speed
sudo dd if=/dev/zero of=/mnt/ssd/test bs=1M count=1000 conv=fdatasync

# Unmount a specified device
sudo umount /mnt/sd

# Check and repair a filesystem
sudo fsck.ext4 -f /dev/mmcblk1p1