[mythtv-users] MySQL recordedseek regularly getting corrupted

[Nick Morrott]

On 1 December 2016 at 22:37, Jean-Yves Avenard <jyavenard at gmail.com> wrote:
>> Seems to me that focusing on where /tmp is, is a waste of time. /tmp may be
>> an issue when trying to repair the corruption, but I think what you really
>> want is to prevent the corruption, right? If so, I would focus on the things
>> that changed when the corruption started to happen. Two things come to mind,
>> based on what you've told us:
>> 1) The SSD
>> 2) the btrfs file system
>> I would try replacing one of those and seeing if that fixes the problem.
>
> I think you're right on both count.
>
> The issue may be the SSD and/or the BTRFS file system.
> I found a fair number of errors on it.

Can you check to see if your /etc/fstab is mounting any partitions on
the Samsung SSD with the discard option? If it is, remove that option.

In 4.x kernels, Samsung 8xx SSDs are blacklisted for queued (NCQ) TRIM
due to the risk of data loss. Scheduled TRIM (using fstrim and cron)
is the preferred method.

I can't say that this is the cause of this particular data corruption
issue on 14.04 - but it is possible, especially if the 14.04 kernel is
unaware (it could have been backported) of the SSD blacklist and still
uses NCQ TRIM.

Now that you have upgraded to 16.04 you may find messages in dmesg
stating that NCQ TRIM is automatically disabled and that your have a
fstrim cronjob in /etc/cron.cron.weekly or /etc/cron.daily (I'd still
remove discard as a mount option in /etc/fstab for any relevant SSD
partitions).

Cheers,
Nick