From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pigeon.gentoo.org ([208.92.234.80] helo=lists.gentoo.org) by finch.gentoo.org with esmtp (Exim 4.60) (envelope-from ) id 1QraOt-0005Ei-B9 for garchives@archives.gentoo.org; Thu, 11 Aug 2011 18:54:39 +0000 Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id F183F21C1E0; Thu, 11 Aug 2011 18:54:24 +0000 (UTC) Received: from mail-ey0-f171.google.com (mail-ey0-f171.google.com [209.85.215.171]) by pigeon.gentoo.org (Postfix) with ESMTP id B8FEC21C1DF for ; Thu, 11 Aug 2011 18:52:51 +0000 (UTC) Received: by eyg24 with SMTP id 24so1352550eyg.16 for ; Thu, 11 Aug 2011 11:52:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; bh=Df8jhELrjLs21T4Kp/7TUzT5BWq+6O3sbUIB3xAG/fg=; b=QQEal4RAs9L8j/BaN3G4NGmDkxSATI7oqVjfE8zjLfbjOHQDZBbR+JiZJoq1x/ukq1 wq/oh9X96ik+FqmZw2oOcISg4wk1lIfmTbjLW6iy3GQveQn/cNcG5wKlOZdjoHG4wv3n wGxegn/YyoRHO0JuTn6dghShbC6RM+vpEOUZ0= Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 Received: by 10.14.186.131 with SMTP id w3mr2795698eem.99.1313088770909; Thu, 11 Aug 2011 11:52:50 -0700 (PDT) Received: by 10.14.95.141 with HTTP; Thu, 11 Aug 2011 11:52:50 -0700 (PDT) In-Reply-To: References: Date: Thu, 11 Aug 2011 11:52:50 -0700 Message-ID: Subject: Re: [gentoo-user] {OT} USB 3.0 hard drive speed test From: Grant To: gentoo-user@lists.gentoo.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Archives-Salt: X-Archives-Hash: 3c47698efe6326b0265a2c35270f98d3 >>>> I'm testing this USB 3.0 bus-powered hard drive: >>>> >>>> http://www.amazon.com/gp/product/B0041OSQ9S >>>> >>>> and I get: >>>> >>>> # hdparm -tT /dev/sdb >>>> /dev/sdb: >>>> Timing cached reads: =A0 8006 MB in =A02.00 seconds =3D 4004.33 MB/sec >>>> Timing buffered disk reads: 252 MB in =A03.01 seconds =3D =A083.63 MB/= sec >>>> >>>> # hdparm -tT /dev/sdb >>>> /dev/sdb: >>>> Timing cached reads: =A0 8230 MB in =A02.00 seconds =3D 4116.54 MB/sec >>>> Timing buffered disk reads: 252 MB in =A03.02 seconds =3D =A083.55 MB/= sec >>>> >>>> # hdparm -tT /dev/sdb >>>> /dev/sdb: >>>> Timing cached reads: =A0 8446 MB in =A02.00 seconds =3D 4224.36 MB/sec >>>> Timing buffered disk reads: 230 MB in =A03.02 seconds =3D =A076.28 MB/= sec >>>> >>>> Wikipedia says USB 3.0 has transmission speeds of up to 5 Gbit/s. >>>> Doesn't MB/sec denote mega*bytes* per second? >>>> >>>> - Grant >>> >>> 4000MB/s =3D 4Gb/s >> >> OK, I thought "B" designated bytes and "b" designated bits. =A0So when >> you see something like MB/s or Mb/s there's no way to know if it's >> referring to megabits or megabytes? >> >> - Grant > > Nahh, I made a mistake there. 4000MB/S =3D 4GB/S =A0- You are correct, at > least as far as I'm concerned. > > Of course Volker, the man with the answer to everything, just told you > that 80 mega-bit / second was a 'really, really good hard drive' so I > guess we all make mistakes. ;-) > > I was really trying to point out that you ARE getting 80% of the USB > 3.0 spec in the first number which is the speed of communications > across the USB cable talking to the drive interface. Sustained storage As Volker pointed out, I don't think hdparm -T interacts with the USB system at all. I get the same rates whether the USB hard drive is plugged into a 3.0 port or 2.0 port. - Grant > rates of the drive don't have anything to do with that though. That > depends on the drive in the case. > > Cheers, > Mark