From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keld =?iso-8859-1?Q?J=F8rn?= Simonsen Subject: Re: strange performance of raid0 Date: Sun, 15 Feb 2004 17:48:10 +0100 Sender: linux-raid-owner@vger.kernel.org Message-ID: <20040215164810.GA20252@rap.rap.dk> References: <20040215100432.GA19002@rap.rap.dk> <1076838850.28006.6.camel@stoneburner.xwredwing.net> <20040215120525.GA19434@rap.rap.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <20040215120525.GA19434@rap.rap.dk> To: Keld =?iso-8859-1?Q?J=F8rn?= Simonsen Cc: Matt Thrailkill , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Sun, Feb 15, 2004 at 01:05:25PM +0100, Keld J=F8rn Simonsen wrote: > On Sun, Feb 15, 2004 at 01:54:11AM -0800, Matt Thrailkill wrote: > > The you don't get as good performance because hdc1 is slow enough t= o > > really drag it down. Think about it, if reads are all going about > > sequentially, it has to spend alot of time waiting on that 16mb/s d= rive > > compared to the others. >=20 > I would have thought the disks would have worked towards gaining > performance enhancements in some cumulative way, is that not so, in t= heory? >=20 > So why is 3 disks slower than 2? >=20 > > You probably can't get 100mb/s with the two because that would be p= retty > > efficient, and there's probably more overhead than that. > >=20 > > Shouldn't the 80gb drive be going faster than 16mb/s though? Have = you > > checked hdparm to make sure dma and all the goodies are turned on f= or > > it? >=20 > I have a 40 GB segate disk also, on the same motherboard IDE > controller, it runs about 40 MB/s. So yes, the hdc1 > should go faster, and I have measured something like 40 MB/s > on it in idler times. I think it is because it is running other=20 > processes. The machine is a ftp mirror and the disk has RedHat > and Fedora ISO images, so it is quite popular. Hmm, I have ext3 filesystems, and they are updating the atime in the inodes. Could that be it? inode flushing obstructing the striping? Best regards Keld - To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html