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Periodically run the one-liner above if/when there are significant changes to the files in /usr/
= Before rebooting, add following to /etc/fstab : =
/squashed/usr/usr.sfs /squashed/usr/ro squashfs loop,ro 0 0
usr /usr aufs udba=reval,br:/squashed/usr/rw:/squashed/usr/ro 0 0
No need to delete original /usr/ ! (unless you don't care about recovery). Also AuFS does not work with XFS
Check SATA controller type.
6.0 Gbps - SATA III
3.0 Gbps - SATA II
1.5 Gbps - SATA I
To get most of you HDD/SSD driver you need to make sure you partition are aligned, if not the speed penalty can be up to 50% slower!
this simple one liner will check to see if each partition start sector is divided by 512
you need to change sda with your driver
if you find the one of your partitions is not aligned use gparted to move the start sector of the partition to be divided of 512
if you still get a permissions error using sudo, then nano the file:
sudo nano -w /sys/block/sdb/queue/rotational
and change 1 to 0
says that this will "help the block layer to optimize a few decisions"