From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net ([212.227.15.15]:57015 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750968AbbKOGaN (ORCPT ); Sun, 15 Nov 2015 01:30:13 -0500 Received: from thetick.localnet ([93.181.44.4]) by mail.gmx.com (mrgmx003) with ESMTPSA (Nemesis) id 0MUZKF-1ZpuRl42xn-00RKaK for ; Sun, 15 Nov 2015 07:30:11 +0100 From: Marc Joliet To: linux-btrfs@vger.kernel.org Subject: Re: Using Btrfs on single drives Date: Sun, 15 Nov 2015 07:30:08 +0100 Message-ID: <1900961.ItTdAumaJ1@thetick> In-Reply-To: References: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart10804018.YfkSl782Ae"; micalg="pgp-sha256"; protocol="application/pgp-signature" Sender: linux-btrfs-owner@vger.kernel.org List-ID: --nextPart10804018.YfkSl782Ae Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" On Sunday 15 November 2015 04:01:57 Duncan wrote: >audio muze posted on Sun, 15 Nov 2015 05:27:00 +0200 as excerpted: >> I've gone ahead and created a single drive Btrfs filesystem on a 3TB= >> drive and started copying content from a raid5 array to the Btrfs >> volume. Initially copy speeds were very good sustained at ~145MB/s = and >> I left it to run overnight. This morning I ran btrfs fi usage >> /mnt/btrfs and it reported around 700GB free. I selected another fo= lder >> containing 204GB and started a copy operation, again from the raid5 >> array to the Btrfs volume. Copying is now materially slower and slo= wing >> further...it started at ~105MB/s and after 141GB has slowed to aroun= d >> 97MB/s. Is this to be expected with Btrfs of have I come across a b= ug >> of some sort? > >That looks to /me/ like native drive limitations. > [Snip nice explanation] I'll just add that I see this with my 3TB USB3 HDD, too, but also with = my=20 internal HDDs. Old drives (the oldest I had were about 10 years old) a= lso had=20 this problem, only scaled appropriately (the worst was something like 4= 0/60=20 GB/s min./max.). You can also see this very nicely with scrub runs (I use dstat for this= ): =20 they start out at the max., but gradually slow down as they progress. HTH =2D-=20 Marc Joliet =2D- "People who think they know everything really annoy those of us who kno= w we don't" - Bjarne Stroustrup --nextPart10804018.YfkSl782Ae Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part. Content-Transfer-Encoding: 7Bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAABCAAGBQJWSCZxAAoJEL/Q5oYsiHj0cLEP/0io/RHhJnhGYOP45IVCZuXH lgRiWD2tFGwYDMdAx14ZHMSAMIW8hYoD7skZmgNmLm5ebUSbiYUUUL+nfFurQe7n d65ECM1Uv8KgxVvCTYwPKVqB0DcgPlsYxTVfz2kc26DpHaTIbKofvKsrR3eejkWh KwlBItK16/cDfu9toX43gyj+ALfkQu+j6VIE2QYv5AGZ73T6eQesDp8+vI4sQgRq oFUYulJNsbmdVmBX4cOtr+qFuKh08wmJM1mm6JXGziRejiyXQCoNaZKY697eaW9W zJ+qJnhd6Af0m1EiV9XPF+xYsnKVPgmLJKJ72YaTzz+B3FfrNeH9betUSDk/v2rF jeIPQxZwKycYl/5DejSFVG64O8TiGZXE+ouHdYSL4N/Y3aTQSW6E5RdQHVZqVeEp JmVjAbU0i75Q5qjKQZIpsn4j8QwYxhoTe93a9m7WsDZXVgCRML4mYG9jDy7LwQnO D1bzK3ZCpNd2VnD49FlvXxyTIsos+u4U4NGf5uD1pA3yJfXTkLkmbdNvruCZm4xq pr0+McvxJBnZDYd4u7PQrJUse4pUylPoDTqzTlIut6EQLcUC8GF9OlmcbunL6xK9 rYeNkp3QR4gFCYbY3lsyq8OnsgkIZHG28Ocd4AHUuYbMmSOnAp27uddWYCUXavuc J4E1hD9HNxzFWvz/d3TY =z2gs -----END PGP SIGNATURE----- --nextPart10804018.YfkSl782Ae--