From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f68.google.com ([209.85.214.68]:36245 "EHLO mail-it0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751701AbdBFMhf (ORCPT ); Mon, 6 Feb 2017 07:37:35 -0500 Received: by mail-it0-f68.google.com with SMTP id f200so8485763itf.3 for ; Mon, 06 Feb 2017 04:37:35 -0800 (PST) Received: from [191.9.206.254] (rrcs-70-62-41-24.central.biz.rr.com. [70.62.41.24]) by smtp.gmail.com with ESMTPSA id i184sm4163921itf.15.2017.02.06.04.37.32 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 06 Feb 2017 04:37:32 -0800 (PST) Subject: Re: Is it possible to have metadata-only device with no data? To: linux-btrfs@vger.kernel.org References: <14453691486330921@web21h.yandex.ru> <0dbbe15a-59f7-ef0e-1ed6-83fec7ef165a@mendix.com> From: "Austin S. Hemmelgarn" Message-ID: Date: Mon, 6 Feb 2017 07:37:30 -0500 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 2017-02-05 23:26, Duncan wrote: > Hans van Kranenburg posted on Sun, 05 Feb 2017 22:55:42 +0100 as > excerpted: > >> On 02/05/2017 10:42 PM, Alexander Tomokhov wrote: >>> Is it possible, having two drives to do raid1 for metadata but keep >>> data on a single drive only? >> >> Nope. >> >> Would be a really nice feature though... Putting metadata on SSD and >> bulk data on HDD... > > FWIW, it's on the list to be implemented in the future, but there's a lot > more things on that list than devs working on btrfs, and the feature > development and stabilization trend is that features often take much > longer than anticipated, particularly to properly stabilize (to the level > of the rest of btrfs, which is in general stabilizing but not yet fully > stable, so stabilization is relative, here), which has slowed down the > pipeline of new features due to the devs having their hands full > stabilizing currently done but not yet properly stabilized features. There are also a number of higher priority features than this. While it would be a wonderful feature to have, it doesn't exactly have a particularly significant impact on broad usability. Most of the features being actively worked on are trying to gain parity (no pun intended) with other multi-device storage stacks. Working quotas, parity-RAID, hot-spares, and n-way replication are all pretty significant to the usability of BTRFS in a pretty large number of situations, which is a large part of why they (other than n-way replication) are the primary focus right now for development.