Configuring Ext4 Storage Pool with correct Disk Alignment

Calculating the Stride and Stripe-width

• Ext4 Block Size = default 4KiB (not needed to change this value)
• Stride = RAID chunk size / Ext4 block size
• Stripe-width = Number of physical data disks * Stride

Examples

• RAID 0 - 2 Disks - Stripe Size 64 KiB

• Ext4 BS = 4KiB
• Stride = 64 KiB / 4KiB = 16
• Stripe-width = 2 * 16 = 32

mkfs.ext4 -b 4096 -E stride=16,stripe-width=32 <dev>
# or simply:
mkfs.ext4 -E stride=16,stripe-width=32 <dev>

• RAID 1 - Stripe Size - 128 KiB (AKA Chunk Size)

• Ext4 BS = 4KiB
• Stride = 128 KiB / 4KiB = 32
• Stripe-width = 1 * 32 = 32

mkfs.ext4 -b 4096 -E stride=32,stripe-width=32 <dev>
# or simply:
mkfs.ext4 -E stride=32,stripe-width=32 <dev>

• RAID 5 - 4 Disks - Stripe Size 512 KiB

• Ext4 BS = 4KiB
• Stride = 512 KiB / 4KiB = 128
• Stripe-width = 3 * 128 = 384

mkfs.ext4 -b 4096 -E stride=128,stripe-width=384 <dev>
# or simply:
mkfs.ext4 -E stride=128,stripe-width=384 <dev>

• RAID 6 - 10 Disks - Stripe Size 1 MiB = 1024 KiB

• Ext4 BS = 4KiB
• Stride = 1024 KiB / 4KiB = 256
• Stripe-width = 8 * 256 = 2048

mkfs.ext4 -b 4096 -E stride=256,stripe-width=2048 <dev>
# or simply:
mkfs.ext4 -E stride=256,stripe-width=2048 <dev>