From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266757AbUBMF4S (ORCPT ); Fri, 13 Feb 2004 00:56:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266775AbUBMF4S (ORCPT ); Fri, 13 Feb 2004 00:56:18 -0500 Received: from willy.net1.nerim.net ([62.212.114.60]:26893 "EHLO willy.net1.nerim.net") by vger.kernel.org with ESMTP id S266757AbUBMF4Q (ORCPT ); Fri, 13 Feb 2004 00:56:16 -0500 Date: Fri, 13 Feb 2004 06:53:50 +0100 From: Willy Tarreau To: Timothy Miller Cc: Linux Kernel Mailing List Subject: Re: File system performance, hardware performance, ext3, 3ware RAID1, etc. Message-ID: <20040213055350.GG29363@alpha.home.local> References: <402C0D0F.6090203@techsource.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <402C0D0F.6090203@techsource.com> User-Agent: Mutt/1.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 12, 2004 at 06:32:31PM -0500, Timothy Miller wrote: > For writes, iozone found an upper bound of about 10megs/sec, which is > abysmal. Typically, I'd expect writes to be faster (on a single drive) > than reads, because once the write is sent, you can forget about it. > You don't have to wait around for something to come back, and that > latency for reads can hurt performance. The OS can also buffer writes > and reorder them in order to improve efficiency. It depends on the disk too. Lots of disks (specially IDE) are far slower on writes than they are on reads. > The 3ware has this write cache that you can turn on or off. With it > off, it ensures that writes make it to the disks in order. With it on, > it will reorder writes more efficiently. However, I noticed that the > performance only went up to about 16meg/sec with the cache ON. I don't think that the FS type has much importance once the cache is ON. > IMPORTANT QUESTION: Is there any metadata anywhere in the swap > partition (when it's not in use) that I need to save before I fill it > with zeros? No, there's nothing to save, but you'll have to rebuild the swap at the end of your tests : mkswap /dev/sga3 I too often use the swap partition for testing purpose or for temporary storage ; it's easy to do a swapoff; mke2fs on it :-) > Also, what do I use as a source for zeros when writing with dd? > "/dev/zero"? yes. but don't try to copy any file from the disk onto this partition, because head seeks will slow things down. > What's the command? How about this: > time dd if=/dev/zero of=/dev/sga3 bs=1024 count=1024 do it like this, but use higher values, particularly for bs which is only 1kB here. Using something like bs=65536 and count=4096 will give you a 256 MB file. > Will that do it? Should I use an offset to avoid any kind of header or > metadata? not needed. Just ensure that you write to the right partition, and better check twice. Regards Willy