From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Mamedov Subject: Re: Write-intent bitmap decreases or increase performance of RAID5? Date: Wed, 30 Jun 2010 11:59:27 +0600 Message-ID: <20100630115927.090751dd@natsu> References: <20100629201153.GA13018@localhost> <20100630111854.006ec4d0@natsu> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/7KVGVfJ0awicodSe0PthVAm"; protocol="application/pgp-signature" Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Mikael Abrahamsson Cc: Shaochun Wang , "linux-raid@vger.kernel.org" List-Id: linux-raid.ids --Sig_/7KVGVfJ0awicodSe0PthVAm Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Wed, 30 Jun 2010 07:54:55 +0200 (CEST) Mikael Abrahamsson wrote: > On Wed, 30 Jun 2010, Roman Mamedov wrote: >=20 > > dd if=3D/dev/zero of=3Dzerofile bs=3D1M count=3D2048 conv=3Dfdatasync,= notrunc >=20 > To be a bit more sure about accurate measurement, make sure the amount of= =20 > data you're transferring is twice the amount of RAM in the machine, the=20 > above is only 2 gigs of data. This is not necessary. See the dd man page about the conv=3Dfdatasync switc= h. You can even test with just 256 MB this way, and still get an extremely accurate result. Three consecutive runs with "count=3D256" on a machine with 4GB of RAM: 268435456 bytes (268 MB) copied, 4.76846 s, 56.3 MB/s 268435456 bytes (268 MB) copied, 4.79682 s, 56.0 MB/s 268435456 bytes (268 MB) copied, 4.79307 s, 56.0 MB/s --=20 With respect, Roman --Sig_/7KVGVfJ0awicodSe0PthVAm Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iEYEARECAAYFAkwq3T8ACgkQTLKSvz+PZwhteACdHvzbI4q+LDTqlb1cbGX6Oyll WD8AoIVqMhY8fp/A0g+RA9fR/d0UO4xj =XYyn -----END PGP SIGNATURE----- --Sig_/7KVGVfJ0awicodSe0PthVAm--