Hello everyone!
I'd really like to check if I am missing any steps for setting up a fully "4K sector" aligned storage stack. If there's anyone who knows the correct answer, it would be here.
The goal is to have each Ext4 sector mapped exactly to a physical sector on the SSD. For maximum read/write performance and to have perfectly aligned TRIM support (yes I know about the minor security issue with encryption and TRIM, but the SSD lifetime health is way more important to me).
I'd really like to check if I am missing any steps for setting up a fully "4K sector" aligned storage stack. If there's anyone who knows the correct answer, it would be here.
The goal is to have each Ext4 sector mapped exactly to a physical sector on the SSD. For maximum read/write performance and to have perfectly aligned TRIM support (yes I know about the minor security issue with encryption and TRIM, but the SSD lifetime health is way more important to me).
My stack is SSD -> GPT Partition Table -> LUKS encryption -> LVM volume -> ext4 filesystem, and the whole stack must be aligned to 4096 byte sectors for this to work.
* Partition Table: Every partition MUST be completely aligned (START and END) on MiB boundary (the ending alignment is important too since LUKS can't encrypt partial sectors). Do this by setting GParted's "Align to: MiB" when creating the partition. As the GParted manual explains, this forces the partition to START and END on precise MiB boundaries: "Use MiB alignment for modern operating systems. This setting aligns partitions to start and end on precise mebibyte (1,048,576 byte) boundaries."
* Use GParted to create a "Filesystem: unformatted" partition. Again, it must start and end on precise MiB alignment offsets via the "Align to: MiB" setting.
* Terminal:
# Get device name for the "unformatted" partition, in my case /dev/nvme0n1p3:
fdisk -l
# Ensure that the encrypted payload starts at 1 MiB (2048 * 512 byte sectors):
cryptsetup --key-size 256 --type luks2 --sector-size 4096 --align-payload 2048 luksFormat /dev/nvme0n1p3
# Open the LUKS volume and permanently mark it as "allow discards (TRIM) so that it always opens like that by default:
cryptsetup --allow-discards --persistent open /dev/nvme0n1p3 cryptdata
# Create the LVM volume metadata and enforce "start of payload" alignment at the nearest 1 MiB boundary after the metadata (by default this means the payload starts at 1 MiB):
pvcreate -ffy --metadatatype lvm2 --dataalignment 1m --dataalignmentoffset 0 /dev/mapper/cryptdata
# Create the LVM volume group and force it to divide the volume into aligned 4 MiB chunks (this is the default, but enforcing it just to be sure):
vgcreate -ffy --physicalextentsize 4m data /dev/mapper/cryptdata
# Create a LVM logical volume using all of the space:
lvcreate -y --name root --extents 100%FREE data
# Format as ext4 with 4096 byte (4 KiB) block size:
mkfs.ext4 -F -b 4096 /dev/mapper/data-root
If all of my research of all man pages and tons of old wikis and guides is correct, this will create a stack that's completely aligned to 4 KiB physical sectors.
Is there anything I am missing here, or anything that you would suggest changing? For example, perhaps I should change "--align-payload 2048" to "--align-payload 4096" (what would that do/improve?), which I've seen a few mentions of?
Grateful for any help in clearing this up, or clarifying that my steps are ready to use. It's been a very long research and I'd like to be sure that I am doing everything correctly.
With best regards,
Johnny
* Partition Table: Every partition MUST be completely aligned (START and END) on MiB boundary (the ending alignment is important too since LUKS can't encrypt partial sectors). Do this by setting GParted's "Align to: MiB" when creating the partition. As the GParted manual explains, this forces the partition to START and END on precise MiB boundaries: "Use MiB alignment for modern operating systems. This setting aligns partitions to start and end on precise mebibyte (1,048,576 byte) boundaries."
* Use GParted to create a "Filesystem: unformatted" partition. Again, it must start and end on precise MiB alignment offsets via the "Align to: MiB" setting.
* Terminal:
# Get device name for the "unformatted" partition, in my case /dev/nvme0n1p3:
fdisk -l
# Ensure that the encrypted payload starts at 1 MiB (2048 * 512 byte sectors):
cryptsetup --key-size 256 --type luks2 --sector-size 4096 --align-payload 2048 luksFormat /dev/nvme0n1p3
# Open the LUKS volume and permanently mark it as "allow discards (TRIM) so that it always opens like that by default:
cryptsetup --allow-discards --persistent open /dev/nvme0n1p3 cryptdata
# Create the LVM volume metadata and enforce "start of payload" alignment at the nearest 1 MiB boundary after the metadata (by default this means the payload starts at 1 MiB):
pvcreate -ffy --metadatatype lvm2 --dataalignment 1m --dataalignmentoffset 0 /dev/mapper/cryptdata
# Create the LVM volume group and force it to divide the volume into aligned 4 MiB chunks (this is the default, but enforcing it just to be sure):
vgcreate -ffy --physicalextentsize 4m data /dev/mapper/cryptdata
# Create a LVM logical volume using all of the space:
lvcreate -y --name root --extents 100%FREE data
# Format as ext4 with 4096 byte (4 KiB) block size:
mkfs.ext4 -F -b 4096 /dev/mapper/data-root
If all of my research of all man pages and tons of old wikis and guides is correct, this will create a stack that's completely aligned to 4 KiB physical sectors.
Is there anything I am missing here, or anything that you would suggest changing? For example, perhaps I should change "--align-payload 2048" to "--align-payload 4096" (what would that do/improve?), which I've seen a few mentions of?
Grateful for any help in clearing this up, or clarifying that my steps are ready to use. It's been a very long research and I'd like to be sure that I am doing everything correctly.
With best regards,
Johnny
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