From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from plane.gmane.org ([80.91.229.3]:47980 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750981AbcALBRE (ORCPT ); Mon, 11 Jan 2016 20:17:04 -0500 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1aIna2-0007y7-E9 for linux-btrfs@vger.kernel.org; Tue, 12 Jan 2016 02:17:02 +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 ; Tue, 12 Jan 2016 02:17:02 +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 ; Tue, 12 Jan 2016 02:17:02 +0100 To: linux-btrfs@vger.kernel.org From: Duncan <1i5t5.duncan@cox.net> Subject: Re: 6TB partition, Data only 2TB - aka When you haven't hit the "usual" problem Date: Tue, 12 Jan 2016 01:16:57 +0000 (UTC) Message-ID: References: <20160109202659.GC6060@carfax.org.uk> <20160109210429.GD6060@carfax.org.uk> <5693A8B3.2090508@gmail.com> <5693B7C0.8010903@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: Henk Slager posted on Mon, 11 Jan 2016 21:29:37 +0100 as excerpted: > The Data increments with 1G (or 10G?) chunks if there is no well-fitting > space in existing chunks. One of the devs (Qu?) explained this rather well in a followup to something or other, probably about a week or two ago. I remember replying to the effect of how much more I knew of the exact numbers at the time. Based on that, nominal data chunk size is 1 GiB, on btrfs upto 100 GiB in size (tho real small ones will have smaller data chunk sizes as well, not sure of the small end numbers, tho when mixed-mode was introduced until progs 4.3(.1 I think), mixed-mode was the default below 1 GiB size, and it uses metadata sized chunks). Above 100 GiB, data chunk size increases to 10 GiB. Similarly, metadata chunk sizes are 256 MiB below 100 GiB, I think 1 GiB above. As we're talking multi-TB in this case, obviously well above 100 GiB, data chunk sizes are likely to be 10 GiB, tho I'm not 100% sure if that applies on single device, or only to striped chunks, with 1 GiB strips and stripes of up to 10 GiB if there's 10 devices in the stripe. (As regulars here will know if they've kept track, I use multiple, much smaller btrfs here, the largest of which is 24 GiB per device, pair- device raid1 for both data/metadata, so 48 GiB total fs size, 24 GiB each on two devices in raid1, 24 GiB capacity. Obviously I see only 1 GiB data chunks, smaller of course on my 256 MiB /boot and its backup on the other device, both of which are single-device mixed-mode dup, so 128 MiB capacity.) -- 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