From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ie0-f174.google.com ([209.85.223.174]:45075 "EHLO mail-ie0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754448AbaAUMZo (ORCPT ); Tue, 21 Jan 2014 07:25:44 -0500 Received: by mail-ie0-f174.google.com with SMTP id tp5so3371223ieb.33 for ; Tue, 21 Jan 2014 04:25:43 -0800 (PST) Message-ID: <52DE6747.4050404@gmail.com> Date: Tue, 21 Jan 2014 07:25:43 -0500 From: Austin S Hemmelgarn MIME-Version: 1.0 To: Sandy McArthur CC: Toggenburger Lukas , "linux-btrfs@vger.kernel.org" Subject: Re: Working on Btrfs as topic for master thesis References: <8E968DF3B7EC0D40B67B5A9D25675A6A03FC70@MBXSRV03EDU.edu.local> <52DD148E.3060200@gmail.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 2014-01-21 01:42, Sandy McArthur wrote: > On Mon, Jan 20, 2014 at 7:20 AM, Austin S Hemmelgarn > wrote: >> >> On 2014-01-16 14:23, Toggenburger Lukas wrote: >>> 3. Improving subvolume handling regarding taking recursive snapshots ( https://btrfs.wiki.kernel.org/index.php/Project_ideas#Take_recursive_snapshots ) and taking snapshots of arbitrary directories ( https://btrfs.wiki.kernel.org/index.php/Project_ideas#Snapshot_arbitrary_directories ) >> >> Another option that I would personally love to see would be support for >> write-mostly devices (that is, devices in a RAID1/RAID10 setup that only >> get written too unless the data can't be found elsewhere). This would >> in particular provide an alternative to using bcache/dm-cache (namely an >> SSD and HDD in RAID1 with the HDD set to write-mostly). >> Based on the current development focus, I don't think anybody is working >> on this already (I would be, but I don't have either the time or the >> skills with kernel programming that would be needed). > > Maybe this happens already: Might a similar effect be automatically > achieved by tracking per-device I/O load averages and distributing > reads based on the I/O loads of possible read devices? > That might be the case, it depends on how the I/O load averages are calculated. I actually hadn't realized BTRFS did this, I thought it behaved more like MD RAID (that is, distributing the reads among devices in a un-weighted round-robin fashion).