[CentOS] Errors on an SSD drive

Thu Aug 10 20:12:55 UTC 2017
Warren Young <warren at etr-usa.com>

On Aug 10, 2017, at 2:07 AM, John Hodrien <J.H.Hodrien at leeds.ac.uk> wrote:
> For a well configured desktop that rarely needs to swap, I struggle to see the
> load on the SSD as being significant, and yet obviously the performance of an
> SSD would make it ideal for swap.

I agree.

It’s a bad idea to do without swap even if you almost never use it, because today’s bloated apps often have many pages of virtual memory they rarely or never actually touch.  You want those pages to get swapped out quickly so that the precious RAM can be used more productively; by the buffer cache, if nothing else.

I once used a web application server on a headless VPS that still had GUI libraries linked to its binary because one of the underlying technologies it uses was also used in a GUI app, and it was too difficult to tear all that GUI code out, even if it was never called.  Because the VPS technology didn’t support swap, I directly paid the price for those megs of unused (and unusable!) libraries in my monthly VPS rental fees.

> Coo, I've never seen a disk actually shrink due to failed sectors.  I don't
> think I've got an SSD into a worn state yet to see this.

Me, neither.  I’m pretty sure the spare sector pool’s size isn’t reported to the OS, and the drive isn’t allowed to dip into the sectors it does expose externally for spares.  

When the spare pool is used up, the drive just starts failing in a way that even SMART can see.