From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Elsayed Subject: Re: bcache and SSD over provisioning Date: Wed, 13 Nov 2013 14:30:44 -0800 Message-ID: References: <5283D85B.10904@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-bcache@vger.kernel.org =46rancis Moreau wrote: > Hello Matthew, >=20 > Le 13/11/2013 15:13, Matthew Patton a =C3=A9crit : >> On Wed, 13 Nov 2013 03:42:54 -0500, Francis Moreau >> wrote: >>=20 >>> First I'd like to know if over-provisioning is still needed when >>> bcache is used ? >>=20 >> 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? >>=20 >=20 > That's indeed not really required: my system is for a desktop usage. >=20 >>> - Should I create 2 partitions with one left emtpy and whose size= is >>> roughly 7% of the device size ? >>=20 >> Your SSD already has 7% overprovisioning. For best sustained and >> consistent write performance you'll want to bump it to 25-30%. Yes y= ou >> just need to partition/LVM down to the desired size. >=20 > 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. >=20 > Thanks for your help. Because the raw flash chips are only available in power-of-two sizes. T= he=20 available storage the controller allows access to is 120GB, and it's=20 reserved 8GB for overprovisioning if I'm looking at the right model.