From owner-freebsd-fs@freebsd.org Mon May 13 11:07:34 2019 Return-Path: Delivered-To: freebsd-fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 837D7158AF08 for ; Mon, 13 May 2019 11:07:34 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mailman.ysv.freebsd.org (mailman.ysv.freebsd.org [IPv6:2001:1900:2254:206a::50:5]) by mx1.freebsd.org (Postfix) with ESMTP id 1C1A3745D5 for ; Mon, 13 May 2019 11:07:34 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: by mailman.ysv.freebsd.org (Postfix) id CD7B3158AF07; Mon, 13 May 2019 11:07:33 +0000 (UTC) Delivered-To: fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id BB135158AF06 for ; Mon, 13 May 2019 11:07:33 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mxrelay.ysv.freebsd.org (mxrelay.ysv.freebsd.org [IPv6:2001:1900:2254:206a::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.ysv.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4A0DB745D3 for ; Mon, 13 May 2019 11:07:33 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.ysv.freebsd.org (Postfix) with ESMTPS id 811407261 for ; Mon, 13 May 2019 11:07:32 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id x4DB7WTo020574 for ; Mon, 13 May 2019 11:07:32 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id x4DB7WtA020573 for fs@FreeBSD.org; Mon, 13 May 2019 11:07:32 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: fs@FreeBSD.org Subject: [Bug 237807] ZFS: ZVOL writes fast, ZVOL reads abysmal... Date: Mon, 13 May 2019 11:07:32 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: 12.0-STABLE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: nbe@renzel.net X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: fs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 May 2019 11:07:34 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D237807 --- Comment #3 from Nils Beyer --- (In reply to sigsys from comment #2) the benchmark tool is completely sequential as it is a simple: dd if=3D/dev/zvol/morsleben-grube2/test of=3D/dev/null bs=3D1M ^C 375390208 bytes transferred in 15.330245 secs (24486902 bytes/sec) whereas the ZVOL has been filled before with random data using: dd if=3D/dev/urandom of=3D/dev/zvol/morsleben-grube2/test bs=3D1M ^C 8544845824 bytes transferred in 77.684268 secs (109994546 bytes/sec) "primarycache" and "secondarycache" are disabled for that ZVOL to get real = read speeds... Now, I've followed your advice and tried two identical instances of "dd" reading from the ZVOL. And you are right, I get twice the throughput: 40MB/s now. It still is abysmal if you ask me, but okay... The slow read throughput also exists via the iSCSI connection from a Windows Server (the ZPOOL "morsleben-grub2" is a backup target). So I have to convi= nce the Microsoft iSCSI initiator somehow to create more concurrent reads. Thank you for the pointers... --=20 You are receiving this mail because: You are the assignee for the bug.=