From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from plane.gmane.org ([80.91.229.3]:47960 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752902AbcCSBPv (ORCPT ); Fri, 18 Mar 2016 21:15:51 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1ah5Ua-0004u4-8M for linux-btrfs@vger.kernel.org; Sat, 19 Mar 2016 02:15:48 +0100 Received: from ip98-167-165-199.ph.ph.cox.net ([98.167.165.199]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sat, 19 Mar 2016 02:15:48 +0100 Received: from 1i5t5.duncan by ip98-167-165-199.ph.ph.cox.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sat, 19 Mar 2016 02:15:48 +0100 To: linux-btrfs@vger.kernel.org From: Duncan <1i5t5.duncan@cox.net> Subject: Re: Snapshots slowing system Date: Sat, 19 Mar 2016 01:15:41 +0000 (UTC) Message-ID: References: <201603142303.u2EN3qo3011695@phoenix.vfire> <56E88CB2.6020300@petezilla.co.uk> <56E945E9.1050005@gmail.com> <56EB1CC7.2000602@petezilla.co.uk> <56EC4612.4030206@petezilla.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: Pete posted on Fri, 18 Mar 2016 18:16:50 +0000 as excerpted: > On 03/18/2016 09:17 AM, Duncan wrote: >> So btrfs raid1 has data integrity and repair features that aren't >> available on normal raid1, and thus is highly recommended. >> >> But, raid1 /does/ mean two copies of both data and metadata (assuming >> of course you make them both raid1, as I did), and if you simply don't >> have room to do it that way, you don't have room, highly recommended >> tho it may be. > > This looks like a strong recommendation to get a second SSD for the root > partition and go raid1. Are SSDs more flakey that hdd or are you just a > strong believer in the integrity of raid1? As Austin says, I'd generally consider ssds /more/ reliable than hdds, at least as long as you stay away from the OCZs, etc (but then again, there are spinning rust brands and specific models I stay away from, as well), but the failure modes are a bit different so it's not always as simple as that. But I played with raid1 before btrfs and find the additional data integrity features that btrfs raid1 brings even more compelling, so yes, it would indeed be fair to say that I'm a strong booster of btrfs raid1 in particular. =:^) The roadmapped but still to come feature I'm /really/ looking forward to, however, is N-way-mirroring, because btrfs raid1 is currently very specifically two copies, regardless of how many devices there are, and I would really /really/ like to have the choice of three copies, again, not just for device-failure protection, but because with btrfs checksumming and data integrity, if one copy is found to be bad for whatever reason, be it a crash before all copies were written, or a failing device, a simple bad block on an otherwise fine device, or whatever gamma ray block damage or the like, right now that means the other copy BETTER come out checksum-verified, or that data or metadata is toast, and I'd rest far easier if even if one failed, I knew there was still not just the one copy, but a second, to fall back on as well. With N-way-mirroring, of course that could be 4 or more copies as well, but three is closest to my sweet spot balance between cost and extreme reliability, and I'd very much like to have that choice as an option. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman