From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shaochun Wang Subject: Re: Write-intent bitmap decreases or increase performance of RAID5? Date: Thu, 1 Jul 2010 14:40:44 +0800 Message-ID: <20100701064044.GB6058@localhost> References: <20100629201153.GA13018@localhost> <20100630111854.006ec4d0@natsu> Mime-Version: 1.0 Content-Type: text/plain; charset=gb2312 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: "linux-raid@vger.kernel.org" List-Id: linux-raid.ids On Wed, Jun 30, 2010 at 07:54:55AM +0200, Mikael Abrahamsson wrote: > On Wed, 30 Jun 2010, Roman Mamedov wrote: >=20 > > dd if=3D/dev/zero of=3Dzerofile bs=3D1M count=3D2048 conv=3Dfdatas= ync,notrunc >=20 > To be a bit more sure about accurate measurement, make sure the amoun= t of=20 > data you're transferring is twice the amount of RAM in the machine, t= he=20 > above is only 2 gigs of data. As suggested, I did the test again and got the following result: -bash-4.1$ sudo dd if=3D/dev/zero of=3Dtest.dd bs=3D1M count=3D5000 co= nv=3Dfdatasync,notrunc Password: 5000+0 records in 5000+0 records out 5242880000 bytes (5.2 GB) copied, 63.497 s, 82.6 MB/s -bash-4.1$ sudo dd if=3D/dev/zero of=3Dtest.dd bs=3D1M count=3D5000 co= nv=3Dfdatasync,notrunc 5000+0 records in 5000+0 records out 5242880000 bytes (5.2 GB) copied, 18.1033 s, 290 MB/s =09 I don't know why the second dd becomes 290MB/s and the first 82.6MB/s. --=20 Shaochun Wang(=CD=F5=C9=DC=B4=BA) State Key Laboratory of Computer Science, Institute of Software, Chinese Academy of Sciences -- 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