In my Ubuntu 18.10 neither udev rule or hdparms.conf works. Instead I needed to edit /etc/default/tlp changing DISK_APM_LEVEL_ON_BAT value.
-- You received this bug notification because you are a member of Kernel Packages, which is subscribed to apmd in Ubuntu. https://bugs.launchpad.net/bugs/1650074 Title: Default on battery APM level causes SSD runing very slow Status in Ubuntu: Triaged Status in apmd package in Ubuntu: Triaged Bug description: Installed Ubuntu 16.04 on a Dell 7559 laptop with Crucial MX300 750GB SSD. When power is unplugged, file read/write speed is about 30MB/s consistently. When power is plugged, file read/write speed is about 400~500MB/s consistently. Used hdparm to check SSD status and found APM level is 128 on battery and 254 on power. Edited /etc/hdparm.conf to set apm_battery=254 and after reboot file read/write speed back to normal 400~500MB/s. Not sure if this is a feature or bug but on battery APM level 128 had caused SSD running ridiculously slow (~30MB/s). To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+bug/1650074/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : firstname.lastname@example.org Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp