[colug-432] Solid State Drives (was: SMART HDD Status): Wear Out

[jep200404 at columbus.rr.com]

On Thu, 23 Feb 2012 18:01:56 -0500, Rob Stampfli <res at colnet.cmhnet.org> wrote:

> I started finding discrepancies in what should be
> static files, like those in /var/cache, ...

Since when[1] does one expect /var/cache to be static? 

> ... and they became more and more
> prevalent with each succeeding backup.  (For some reason, these errors
> seemed to cluster in /var/cache.  I found no errors at all in /bin, /usr/bin,
> /sbin, /usr/sbin, or /etc files.) 

Writes wear out flash memory. 

/usr is for stuff that one expects to not change. 
/var is for stuff that one expects to be changed. 

Likely, /usr (and similarly /bin and /sbin) were written to 
when you installed your OS, then left alone, so the sectors 
that content was on did not wear out and stayed the same. 
/var (and perhaps especially /var/cache) was repeatedly 
overwritten until it worn out. 

Mount /var on something less likely to wear out, like RAM, 
or Moon bounce. 

[1] https://secure.wikimedia.org/wikipedia/en/wiki/Filesystem_Hierarchy_Standard