[Bug 1645294] [NEW] Laptop SSD shows write errors after 10 minutes idle on battery

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When Ubuntu puts my SSD to sleep, write errors occur reproducably,
and the file system consequently goes to read-only. This happens
after about 10 minutes of disk inactivity.

Software and hardware details:
- Lubuntu 16.04 LTS (Xenial Xerus)
- Dell Latitude E6530
- ADATA SSD SX900 512GB (5.0.2c)

I have no written down logs of a crash, because the disk is
read-only before output occurs. In a few cases, I could see error
messages in a console window. They said that some write functions to
disk rendered an error. Further messages then said that the disk was
set to read-only (which is the reaction to write errors I prefer).

The problem did not manifest itself when I set up a script to write
the system state to disk regularly ("Heisenbug").

I worked around the problem by adding the following to
/etc/hdparm.conf and rebooting:

/dev/sda {
	# -B apm setting
	apm = 254
	# -B apm setting when on battery
	apm_battery = 254
	# -S standby (spindown) timeout for the drive
	spindown_time = 0
}

In this, "apm = 254" should be the default anyway. The default value
for apm_battery is 128, though. I could not determine the default
value for spindown_time, because I did not find a command to read
this value. However, setting it to 0 was my last step to fixing the
problem.

It appears that spinning down my SSD for power-saving does not work.
I cannot determine whether this is a kernel bug or a firmware
problem. In any case, spinning down a SSD does not appear to be of
much advantage to me. Therefore, it might be better to set the
defaults for SSDs as in my workaround above.

Another problem is that the options of hdparm and in particular
their meaning could be explained better in the man pages.

** Affects: hdparm (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: bot-comment
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Laptop SSD shows write errors after 10 minutes idle on battery
https://bugs.launchpad.net/bugs/1645294
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