From mboxrd@z Thu Jan 1 00:00:00 1970 From: Francis Moreau Subject: Re: bcache and SSD over provisioning Date: Wed, 13 Nov 2013 20:54:38 +0100 Message-ID: <5283D8FE.5000908@gmail.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Adam Berkan , Matthew Patton Cc: "linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-bcache@vger.kernel.org Le 13/11/2013 19:23, Adam Berkan a =E9crit : > On Wed, Nov 13, 2013 at 6:13 AM, Matthew Patton = wrote: >> On Wed, 13 Nov 2013 03:42:54 -0500, Francis Moreau >> 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%.