From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Matthew Patton" Subject: Re: 2 drives btrfs raid1 with one ssd Date: Sun, 15 Dec 2013 20:11:45 -0500 Message-ID: References: <1387155717.6876.29.camel@N900-P> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit Return-path: Received: from nm29-vm1.bullet.mail.ne1.yahoo.com ([98.138.90.63]:49001 "HELO nm29-vm1.bullet.mail.ne1.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751908Ab3LPBML (ORCPT ); Sun, 15 Dec 2013 20:12:11 -0500 In-Reply-To: <1387155717.6876.29.camel@N900-P> Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: linux-bcache@vger.kernel.org, Pavol Cupka On Sun, 15 Dec 2013 20:01:57 -0500, Pavol Cupka wrote: > I would like to use a bcache for btrfs filesystem residing on two > identical disk as raid1 using btrfs' raid (without soft/hard raid). > > Is it possible? if I understood you correctly, no. > I would like to use the same ssd/ssd partition for caching both > drives/mirror. Is this doable? You will have to build the btrfs 'raid' on top of two bcache devices. If the caching device for both devices in the same SSD (partitioned) what's the point? Assuming Btrfs has a similar feature set to MD's Raid1 write-mostly, you could accelerate the one side, and run the other half of the mirror without acceleration. Otherwise I would just use MD's Raid1 and be done with it. Put btrfs/ext4/xfs on top as you like. Does your intended workload really benefit from putting an SSD into the mix?