Re: [GIT PULL 18/25] lightnvm: set target over-provision on create ioctl

[Matias BjÃrling]

On 01/05/2018 08:52 PM, Javier Gonzalez wrote:
> > On 5 Jan 2018, at 20.33, Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote:
> >
> > On 01/05/2018 05:16 AM, Matias BjÃrling wrote:
> > > From: Javier GonzÃlez <javier@xxxxxxxxxxxx>
> > >
> > > Allow to set the over-provision percentage on target creation. In case
> > > that the value is not provided, fall back to the default value set by
> > > the target.
> > >
> > > In pblk, set the default OP to 11% of the total size of the device
> >
> > > +#define PBLK_DEFAULT_OP (11)
> >
> > Hi,
> > Just curious -- where does 11 come from?  Is it a spec value?
>
> 11 stands for 11% over-provisioning for the media to allow garbage
> collection. Different SSDs have different values based on the targeted
> workload - 11% is a common default value for standard drives.
>
> The spec. does not specify any default values of over-provisioning.
>
> Javier.

I think what Randy means is, why is the value not 20% or 7%, which is 
the traditional over-provisioning on SSDs.