Re: bcache and SSD over provisioning

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

Le 13/11/2013 19:23, Adam Berkan a écrit :
> On Wed, Nov 13, 2013 at 6:13 AM, Matthew Patton <pattonme-/E1597aS9LQAvxtiuMwx3w@public.gmane.org> wrote:
>> On Wed, 13 Nov 2013 03:42:54 -0500, Francis Moreau <francis.moro@gmail.com>
>> 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?
>>
>>
>>>   - Should I create 2 partitions with one left emtpy and whose size is
>>> roughly 7% of the device size ?
>>
> bcache has a pretty flash friendly write pattern, so you probably
> don't need a huge lot of empty space.  The 7% might in fact be enough,
> but bumping it up to 10%-12% wouldn't hurt.  I think the >25% numbers
> are more relevant for non-flash friendly writes (like random writes).
> In that case you definitely want lots of free space.

Thanks for your enlightment.

I'll probably go for 10%.