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Re: NVMe SSD and discard mount option

On Tue, May 09, 2017 at 11:02:46AM -0400, Dan Ritter wrote:
> On Tue, May 09, 2017 at 03:35:04PM +0200, David Guyot wrote:
> > Hello, there.
> > 
> > I recently loaned a server with NVMe SSD and saw, during my research on
> > the relevance of the discard mount option for them, that its use is
> > discouraged for NVMe SSDs. Why? Does NVMe SSDs not need trimming? Is it
> > integrated in the NVMe driver for Linux?
> Intel, among other NVMe SSD manufacturers, recommends using
> fstrim periodically rather than enabling continuous trimming
> with the discard option.
> They don't specifically state why, but I will hazard a guess
> that performance is impacted during a trim, and doing so for
> a short period once a day or once a week is more useful than
> decreasing performance all the time.

Evidence from Ted Ts'o:


which boils down to:

A) yes, there's a performance impact
B) the systems which listen to TRIM commands do better on large
   allocations than on small, so batching them up with fstrim
   called by cron is preferred.


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