[CentOS] Samsung evo 840 fixes

Tue Nov 10 21:43:48 UTC 2015
Gordon Messmer <gordon.messmer at gmail.com>

On 11/10/2015 12:00 PM, Christer Solskogen wrote:
> This is the first I found.
> http://linux.slashdot.org/story/15/07/30/1814200/samsung-finds-fixes-bug-in-linux-trim-code 

That bug isn't specific to Samsung drives.  It affected all SSDs used in 
raid0 and raid10 configurations.

> and https://bugs.launchpad.net/ubuntu/+source/fstrim/+bug/1449005

That's a different bug, entirely.  The bug above was a Linux bug, where 
this is a drive firmware bug.  It's worked around in Linux by 
blacklisting NCQ TRIM for Samsung's drives.

The ATA_HORKAGE_NO_NCQ_TRIM flag was introduced in 3.13.  I don't see it 
in CentOS 7's kernel, so it's almost certainly not in C6 either.

You're probably better off disabling NCQ or just testing to see if you 
need TRIM at all.  Particularly if you leave some space unallocated on 
the drive (TRIM it if you were previously using it), many newer drives 
manage free blocks very well, and see little or no performance hit for 
systems that don't use TRIM.