From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay3-d.mail.gandi.net ([217.70.183.195]:55870 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751092AbaFPLS2 convert rfc822-to-8bit (ORCPT ); Mon, 16 Jun 2014 07:18:28 -0400 From: =?ISO-8859-1?Q?Sw=E2mi?= Petaramesh To: Austin S Hemmelgarn Cc: Linux BTRFS Subject: Re: BTRFS, SSD and single metadata Date: Mon, 16 Jun 2014 13:18:24 +0200 Message-ID: <4823159.jCObc9Zrv0@vajra> In-Reply-To: <539ED083.5050705@gmail.com> References: <1723493.aXdklhDgAK@vajra> <539ED083.5050705@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Sender: linux-btrfs-owner@vger.kernel.org List-ID: Hi Austin, and thanks for your reply. Le lundi 16 juin 2014, 07:09:55 Austin S Hemmelgarn a écrit : > > What mkfs.btrfs looks at is > /sys/block//queue/rotational, if that is 1 it knows > that the device isn't a SSD. I believe that LVM passes through whatever > the next lower layer's value is, but dmcrypt (and by extension LUKS) > always force it to a 1 (possibly to prevent programs from using > heuristics for enabling discard) In the current "running condition", the system clearly sees this is *not* rotational, even thru the LVM/dmcrypt stack : # mount | grep btrfs /dev/mapper/VG-LINUX on / type btrfs (rw,noatime,seclabel,compress=lzo,ssd,discard,space_cache,autodefrag) # ll /dev/mapper/VGV-LINUX lrwxrwxrwx. 1 root root 7 16 juin 09:21 /dev/mapper/VG-LINUX -> ../dm-1 # cat /sys/block/dm-1/queue/rotational 0 ...However, at mkfs.btrfs time, it migth well not have seen it, as I made it from a live USB key in which both the lvm.conf and crypttab had not been taylored to allow "trim" commands... However, now that the FS is created, I still wonder whether I should use a rebalance to change the metadata from DUP to SINGLE, or if Id' better stay with DUP... Kind regards. -- Swâmi Petaramesh http://petaramesh.org PGP 9076E32E