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When invoking the hdparm command to securely erase devices e.g. ATA SECURE ERASE, the output hdparm -I /dev/sda and hdparm -I /dev/sdb differ with AHCI enabled and disabled.

Both devices are SATA hard drives.

Establishing state

  1. Both /dev/sda and /dev/sdb have the data & power cable plugged in
  2. The device boots with a Linux LiveCD
  3. AHCI is disabled
  4. When the command hdparm -I /dev/sda and hdparm -I /dev/sdb is run, both drives appear as frozen.

The following steps are taken in an attempt to 'unfreeze' the drive.

  1. Both /dev/sda and /dev/sdb only have the data cable plugged in. The power cable is not plugged in.
  2. AHCI remains disabled.
  3. Boot the device with a Linux LiveCD.
  4. Once booted, both the devices have the power cables plugged in.
  5. When the command hdparm -I /dev/sda and hdparm -I /dev/sdb is run, the former displays a frozen state and the latter as not frozen.

The following steps are taken to 'unfreeze' /dev/sda

  1. The data cable remains plugged in for /dev/sda
  2. AHCI is enabled.
  3. Boot the device with a Linux LiveCD
  4. Once booted, the power cable is plugged into /dev/sda
  5. When the command hdparm -I /dev/sda is run, the drive is no longer frozen.

Why would enabling AHCI affect /dev/sda whist disabling AHCI not affect /dev/sdb when 'unfreezing' the devices?

  • Random guess: BIOS does something differently, maybe a SATA reset would do similar. AHCI on is usually a better choice anyway (at least if the alternative is some pre-AHCI emulation). – derobert Jan 16 at 15:49

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