From owner-freebsd-fs@FreeBSD.ORG Tue Mar 15 15:38:56 2011 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 51FAF106566B for ; Tue, 15 Mar 2011 15:38:56 +0000 (UTC) (envelope-from lopez.on.the.lists@yellowspace.net) Received: from mail.yellowspace.net (mail.yellowspace.net [80.190.192.217]) by mx1.freebsd.org (Postfix) with ESMTP id CBFF78FC08 for ; Tue, 15 Mar 2011 15:38:55 +0000 (UTC) Received: from furia.intranet ([188.174.148.157]) (AUTH: CRAM-MD5 lopez.on.the.lists@yellowspace.net, SSL: TLSv1/SSLv3, 256bits, CAMELLIA256-SHA) by mail.yellowspace.net with esmtp; Tue, 15 Mar 2011 15:56:52 +0100 id 027C18CE.000000004D7F7E34.00000DB8 Message-ID: <4D7F7E33.7050103@yellowspace.net> Date: Tue, 15 Mar 2011 15:56:51 +0100 From: Lorenzo Perone User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.15) Gecko/20110303 Thunderbird/3.1.9 MIME-Version: 1.0 To: freebsd-fs@freebsd.org Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: gmirror performance X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 15 Mar 2011 15:38:56 -0000 Hi @ list, Hi Pawel, just a question about gmirror performance. I have 2 15k SAS drives, mirrored by gmirror. the mirror was setup like this (like manpage example): gmirror label -v -b split -s 2048 mirr0 da0 da1 on a partition of this drive, I make the following test: # dd if=/dev/zero bs=1m count=2000 of=/mnt/2gigfile.dat 2000+0 records in 2000+0 records out 2097152000 bytes transferred in 11.203763 secs (187182824 bytes/sec) # umount /mnt # mount /dev/mirror/mirr0p4 /mnt # dd if=/mnt/2gigfile.dat of=/dev/null bs=1m 2000+0 records in 2000+0 records out 2097152000 bytes transferred in 12.061197 secs (173875942 bytes/sec) I'd expect read performance to be noticeably higher than write performance. Why is it not the case? Wrong expectation? :/ Further Details: - FreeBSD 8.2-STABLE #0: Tue Mar 15 01:34:07 UTC 2011 - Underlying storage driver is the fresh, just MFC'd mps(4) for the DELL PERC H200A controller (so it could be related to that, as well). - Using bs=8k gets better results (180783854 bytes/sec), but this may be caused by other factors. - The filesystem is UFS with soft-updates (newfs -U). Thanx for listening, and for all the nice GEOMs we have @ FreeBSD land :) Regards, Lorenzo