Poor performance after reinstalling to a USB drive

Solution 1:

Apart from the fact that accessing the drive via USB is inherently slower than via SATA (i.e. a "normal" HDD or especially SSD will be noticeably/much faster than an USB drive), one cause of your current setup being slower may be partition misalignment. I'm not sure if USB flash drives are any different, but usually SSD drives have large physical sectors so it's important that partitions are aligned with the start of a physical sector.

You can use gparted to check if the partitions are aligned and to re-align them if necessary (you'll need to boot from another USB to make any changes to your current one)

UPDATE: One way to check if a partition is aligned in gparted is to right-click on the partition, select Information from the menu and check First Sector parameter there. Make sure the number there is a multiple of a... err... alignment factor. 1024 (1MB) is a good number to use... so just make sure it's a multiple of 1024:

I'm pretty sure the absence of swap should not make things slower - but you won't be able to use more RAM than you physically have.

Logical partitions are just as fast as primary ones, provided they all aligned properly.