From owner-freebsd-bugs@FreeBSD.ORG Sat Aug 15 14:20:07 2009 Return-Path: Delivered-To: freebsd-bugs@hub.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 29BFE106568F for ; Sat, 15 Aug 2009 14:20:07 +0000 (UTC) (envelope-from gnats@FreeBSD.org) Received: from freefall.freebsd.org (freefall.freebsd.org [IPv6:2001:4f8:fff6::28]) by mx1.freebsd.org (Postfix) with ESMTP id E03E98FC64 for ; Sat, 15 Aug 2009 14:20:06 +0000 (UTC) Received: from freefall.freebsd.org (gnats@localhost [127.0.0.1]) by freefall.freebsd.org (8.14.3/8.14.3) with ESMTP id n7FEK6O8025856 for ; Sat, 15 Aug 2009 14:20:06 GMT (envelope-from gnats@freefall.freebsd.org) Received: (from gnats@localhost) by freefall.freebsd.org (8.14.3/8.14.3/Submit) id n7FEK64d025855; Sat, 15 Aug 2009 14:20:06 GMT (envelope-from gnats) Resent-Date: Sat, 15 Aug 2009 14:20:06 GMT Resent-Message-Id: <200908151420.n7FEK64d025855@freefall.freebsd.org> Resent-From: FreeBSD-gnats-submit@FreeBSD.org (GNATS Filer) Resent-To: freebsd-bugs@FreeBSD.org Resent-Reply-To: FreeBSD-gnats-submit@FreeBSD.org, Oles Hnatkevych Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 94EA71065691 for ; Sat, 15 Aug 2009 14:15:08 +0000 (UTC) (envelope-from nobody@FreeBSD.org) Received: from www.freebsd.org (www.freebsd.org [IPv6:2001:4f8:fff6::21]) by mx1.freebsd.org (Postfix) with ESMTP id 83FE18FC72 for ; Sat, 15 Aug 2009 14:15:08 +0000 (UTC) Received: from www.freebsd.org (localhost [127.0.0.1]) by www.freebsd.org (8.14.3/8.14.3) with ESMTP id n7FEF7Bg037396 for ; Sat, 15 Aug 2009 14:15:07 GMT (envelope-from nobody@www.freebsd.org) Received: (from nobody@localhost) by www.freebsd.org (8.14.3/8.14.3/Submit) id n7FEF7Yk037395; Sat, 15 Aug 2009 14:15:07 GMT (envelope-from nobody) Message-Id: <200908151415.n7FEF7Yk037395@www.freebsd.org> Date: Sat, 15 Aug 2009 14:15:07 GMT From: Oles Hnatkevych To: freebsd-gnats-submit@FreeBSD.org X-Send-Pr-Version: www-3.1 Cc: Subject: kern/137797: gmirror split does not improve performance X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 15 Aug 2009 14:20:07 -0000 >Number: 137797 >Category: kern >Synopsis: gmirror split does not improve performance >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Sat Aug 15 14:20:06 UTC 2009 >Closed-Date: >Last-Modified: >Originator: Oles Hnatkevych >Release: FreeBSD 7.2 >Organization: >Environment: >Description: Mirror is created with gmirror on ad8 and ad10 ad8: 476940MB at ata4-master SATA150 ad10: 476940MB at ata5-master SATA150 Geom name: ar1 State: COMPLETE Components: 2 Balance: split Slice: 4096 Flags: NONE GenID: 0 SyncID: 1 mirror/ar1 COMPLETE ad8 ad10 The split algorithm does not improve any performance. Even simple dd with block size 1M has the same speed as a single drive, while two dd's on singe drive run simultaneously proove that SATA throughput is not a bottleneck. >How-To-Repeat: gmirror label ar1 ad8 ad10 dd if=/dev/ad8 of=/dev/null bs=1M count=500 dd if=/dev/mirror/ar1 of=/dev/null bs=1M count=500 both give the same speed (around 80MB/s for Seagate 500GB SATA drives) but dd if=/dev/ad8 of=/dev/null bs=1M count=500 & dd if=/dev/ad10 of=/dev/null bs=1M count=500 show that in parallel they do provide data faster. BTW, the performance of a RAID1 created with the atacontrol is a bit better then gmirror. >Fix: >Release-Note: >Audit-Trail: >Unformatted: