When dealing with RAID arrays in Linux, you might encounter the error mount: unknown filesystem type 'linux_raid_member' when trying to mount a single RAID disk. This happens because the system recognizes the disk as part of a RAID array rather than a standalone filesystem.

Attempting to force mount with -t ext4 typically fails because:

• The RAID metadata takes priority over the filesystem
• The disk isn't properly recognized as a standalone device
• There might be residual RAID signatures confusing the system

For RAID 1 arrays, you have several approaches:

Method 1: Using mdadm in Degraded Mode

# Create a degraded RAID array
mdadm --assemble --force /dev/md0 /dev/sdc1
# Mount the array 
mount /dev/md0 /mnt/test

Method 2: Mounting Directly with Offset

If you know the exact filesystem offset:

# First find the offset (example for ext4)
mdadm --examine /dev/sdc1 | grep "Data Offset"
# Then mount with offset (example: 2048 sectors)
mount -o offset=$((2048*512)) /dev/sdc1 /mnt/test

When working with virtual disks in ESXi:

• Ensure the disk isn't locked by the hypervisor
• Check for proper SCSI controller configuration
• Verify disk presentation mode (independent/persistent)

For advanced users needing forensic access:

# Use losetup to create a block device
losetup -f -o $((2048*512)) /dev/sdc1
# Then mount the loop device
mount /dev/loop0 /mnt/test

Always verify before mounting:

# Check RAID status
mdadm --detail /dev/md0
# Verify filesystem integrity
fsck -n /dev/md0

When dealing with software RAID arrays in Linux, you'll frequently encounter the linux_raid_member filesystem type. This isn't a regular filesystem but rather a metadata marker indicating the disk is part of a RAID array. The system refuses to mount it directly because:

• The disk contains RAID metadata headers
• The actual filesystem (ext4, xfs, etc.) is layered beneath the RAID structure
• Mounting individual members could corrupt array consistency

For a RAID 1 (mirror) array where you only have one disk available, here are the correct approaches:

# First examine the RAID metadata
mdadm --examine /dev/sdc1

# Output will show:
# /dev/sdc1:
#           Magic : a92b4efc
#         Version : 1.2
#     Feature Map : 0x1
#      Array UUID : 7ab6b123:1a2b3c4d:5e6f7g8h
#            Name : myserver:0  (local to host myserver)
#    Creation Time : Wed Jan  1 12:00:00 2020
#       Raid Level : raid1

If you need to access data without reassembling the array:

# Find the data offset (typically 4096 sectors)
fdisk -lu /dev/sdc
# Look for: "Partition 1: Start=2048, End=...", then calculate offset=2048*512=1048576

# Mount using offset (adjust numbers based on your fdisk output)
mount -o ro,offset=1048576 -t ext4 /dev/sdc /mnt/test

A cleaner approach for read-only access:

# Assemble as degraded array
mdadm --assemble --run --force /dev/md0 /dev/sdc1

# Verify array status
cat /proc/mdstat

# Now mount normally
mount /dev/md0 /mnt/test

• Always use -o ro for read-only mounting initially
• Backup critical data before attempting write operations
• For VM environments like ESXi, ensure disk is properly detached
• Consider using losetup with offset for safer exploration

When dealing with virtual disks in VMware environments:

# Check for VMFS signatures that might interfere
blkid /dev/sdc1

# If present, wipe RAID signature (DANGEROUS - data loss potential)
mdadm --zero-superblock /dev/sdc1