setup-storage+gpt: alignment aware?
blacky+fai at fluffbunny.de
Mon Mar 19 23:32:51 CET 2012
(or should I address Michael personally since he's probably the only one
who can answer this?)
Does the setup-storage tool try to create properly aligned GPT
partitions? Reason for asking is a somewhat discouraging information on
Hard disk manufacturers are transitioning to 4096-byte sectors. As of
2010, the first
such drives continue to present 512-byte physical sectors to the OS, so
performance can result when the drive's (hidden) internal 4 KiB sector
not coincide with the 4 KiB logical blocks, clusters and virtual memory
in many operating systems and file systems. This is a particular problem
when the drive is forced to perform two read-modify-write operations to
single misaligned 4 KiB write operation.
Such a misalignment occurs by default if the first partition is placed
after the GUID partition table, as the next block is LBA 34. The next 4
begins with LBA 40.
has a detailed explanation how to create a properly aligned partition table.
my current disk_config prototype
disk_config disk1 disklabel:gpt-bios
primary swap 8G swap sw
primary - 4G- - -
vg vg_system disk1.2
vg_system-root / 4G-12G xfs rw
resulting partition table
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Number Start End Size File system Name Flags
1 63s 16777278s 16777216s linux-swap(v1) primary
2 16777279s 41942766s 25165488s primary lvm
3 41942767s 41943006s 240s primary bios_grub
Additional question 1)
What is the difference between disklabel:gpt and disklabel:gpt-bios?
Refering to http://wiki.fai-project.org/wiki/Setup-storage 'gpt-bios'
should not be a valid keyword: disklabel:(msdos|gpt)
Additional question 2)
Is there a way to make setup-storage create the gpt bios partition as
instead of 3? Rationale: Nothing technical. Just a cosmetical issue:
It looks better
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