disable uas for usb ssd

Some external SSDs ship with firmware that (on Linux) will bug out your USB hubs unless you disable UAS (USB Attached SCSI). You can disable UAS and force the drive to operate in USB Mass Storage mode by editing the kernel command line options in the grub.cfg. The canonical way to do this is to edit /etc/default/grub and append this to the value with the key GRUB_CMDLINE_LINUX_DEFAULT:

Where XXXX:YYYY are the hexadecimal identifiers of the device manufacturer and model respectively when you do a lsusb.

Then, do grub-mkconfig >> /some/file and copy the file to your /boot/grub/grub.cfg (make sure to back up your original in case you mess up!).

This can reduce performance in multithreaded IO, but it depends on your situation.