From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.virtall.com ([178.63.195.102]:51127 "EHLO mail.virtall.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753315AbaEPUll (ORCPT ); Fri, 16 May 2014 16:41:41 -0400 Date: Fri, 16 May 2014 21:41:35 +0100 From: Tomasz Chmielewski To: Calvin Walton Cc: "linux-btrfs@vger.kernel.org" Subject: Re: RAID-1 - suboptimal write performance? Message-ID: <20140516214135.23fefc39@s9> In-Reply-To: <1400263584.979.17.camel@sasami.ottawa.blindsidenetworks.com> References: <20140516164815.1c33149b@s9> <1400263584.979.17.camel@sasami.ottawa.blindsidenetworks.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Fri, 16 May 2014 14:06:24 -0400 Calvin Walton wrote: > No comment on the performance issue, other than to say that I've seen > similar on RAID-10 before, I think. > > > Also, what happens when the system crashes, and one drive has > > several hundred megabytes data more than the other one? > > This shouldn't be an issue as long as you occasionally run a scrub or > balance. The scrub should find it and fix the missing data, and a > balance would just rewrite it as proper RAID-1 as a matter of course. It's similar (writes to just one drive, while the other is idle) when removing (many) snapshots. Not sure if that's optimal behaviour. -- Tomasz Chmielewski http://wpkg.org