Re: bcache and SSD over provisioning

[Francis Moreau <francis.moro-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hello Matthew,

Le 13/11/2013 15:13, Matthew Patton a écrit :
> On Wed, 13 Nov 2013 03:42:54 -0500, Francis Moreau  
> <francis.moro-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> 
>> First I'd like to know if over-provisioning is still needed when
>> bcache is used ?
> 
> it's needed for any decent, sustained write load if you don't want  
> performance to crash thru the floor. But it doesn't sound like this is  
> your use case. Are you sustaining 5000+ write IOPs?
> 

That's indeed not really required: my system is for a desktop usage.

>>   - Should I create 2 partitions with one left emtpy and whose size is
>> roughly 7% of the device size ?
> 
> Your SSD already has 7% overprovisioning. For best sustained and  
> consistent write performance you'll want to bump it to 25-30%. Yes you  
> just need to partition/LVM down to the desired size.

Hmm, I don't see what makes you think that my SSD has already 7%
overprovisioning ? Actually I don't think it's the case.

Thanks for your help.