On 5 Jan 2018, at 20.53, Matias Bjørling [off-list ref] wrote:

On 01/05/2018 08:52 PM, Javier Gonzalez wrote:

quoted

quoted

On 5 Jan 2018, at 20.33, Randy Dunlap [off-list ref] wrote:

On 01/05/2018 05:16 AM, Matias Bjørling wrote:

quoted

From: Javier González <redacted>

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

quoted

+#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.

We decided 11% based on customer input, but 7% and 20% are also good
default values. I'm ok with having any of those as default - anyone
caring about OP will define the value on target creation, which is the
primary objective of this patch.

Javier