From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tyler Subject: Re: read vs write Date: Mon, 25 Jul 2005 05:34:05 -0700 Message-ID: <42E4DC3D.1050900@dtbb.net> References: <42E4BFC1.7070905@stesmi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from outbound04.telus.net ([199.185.220.223]:16572 "EHLO priv-edtnes27.telusplanet.net") by vger.kernel.org with ESMTP id S261158AbVGYMeG (ORCPT ); Mon, 25 Jul 2005 08:34:06 -0400 In-Reply-To: Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Saswat Praharaj Cc: Stefan Smietanowski , linux-ide@vger.kernel.org My only suggestion would be to do some research using google. a) 100MB/sec is an interface specification, anotherwords, the bus it=20 sits on, can do 100MB/sec. Take into account the fact that you may hav= e=20 more than one hard drive on the same bus, and you soon figure out why=20 maxtor felt 133MB/sec may be useful, now that there are drives that can= =20 do over 50MB/sec, multiply that by 2, and you are at or above the=20 100MB/sec bus rating. The PCI bus itself (the bus the IDE interface=20 attaches to and transfers across to the CPU), in 32bit, 33mhz form only= =20 has a theoretical limit of 133MB/sec itself. b) I'm guessing your processor is holding you back, or the chipset, or=20 the chipset drivers, or any combination therein. My first test would b= e=20 to put the drive in a faster system. Yes, I know your read speed was=20 higher, but reads *tend* to be higher to begin with. Thinking about=20 this again, and after reading the page i posted below, I would say you=20 are already hitting the drives limits, even without hitting a=20 motherboard/cpu limit, other than possibly the burst speed, which may b= e=20 slightly higher on an ata100 controller. c) Here is possibly a better example than the highway: You buy a new=20 car off the lot these days, and it comes with tires, that are *capable*= =20 of 150mph continuosly... does that mean automatically mean your car is=20 capable of running that fast? no. If you put 4 inch exhaust on your=20 vehicle, does that mean your engine will be able to flow at a rate=20 and/or pressure that can take full advantage of the 4 inch exhaust=20 systems capacity? no. Your speedometer goes to 160mph, does that mean= =20 your car goes that fast? no. and as a side note, 25MB/sec on a 400mhz machine, is an excellent speed= ,=20 as is 58mb/sec read speed. I would stop complaining or looking for=20 something to blame, and realize the hardware is at its limits. I=20 actually doubt that your barracuda drive is doing 58mb/sec, other than=20 possibly burst transfers. try googling a little bit, and find reviews and information such as thi= s=20 page:=20 http://www.xbitlabs.com/articles/storage/display/seagate-barracuda-ata4= =2Ehtml Regards, Tyler. Saswat Praharaj wrote: >yups I meant MBps ..thanks for correcting me . > >However, I dont agree with your ford/road example. > >I just checked the product specification of STA340016A (seagate) .=20 > >Here is what they claim :=20 > >[ This manual describes the functional, mechanical and interface spec= ifi- >cations for the ST380021A, ST360021A, ST340016A and ST320011A. >These drives provide the following key features: >=B7 7,200-RPM spindle speed and 2-Mbyte buffer combine for superior > desktop performance >=B7 High instantaneous (burst) data-transfer rates (up to 100 Mbytes p= er > second) using Ultra DMA mode 5 ] > >I have found average seek time is little faster (around 1ms) for read >than write. >Still that doesn't justify the write speed of 15-20 MBps and 55-60 >MBps for read. > >Can anyone help me understading how/why write is different than read. > >Thanks and Regards, >Saswat > >On 7/25/05, Stefan Smietanowski wrote: > =20 > >>-----BEGIN PGP SIGNED MESSAGE----- >>Hash: SHA1 >> >>Hi Saswat. >> >> =20 >> >>>Moreover, I am wondering if I could achieve the 100Mbps read speed a= s >>>claimed by different vendors.For me , It should ideally be 100 Mbps = as >>>I am using a 80 conductor cable and UDMA 5.Why then I am getting 58 >>>Mbps max . . >>> =20 >>> >>If you mean Mbps then you are already above it. 100Mbps =3D 12.5MB/s >>give or take and both speeds are above that. >>I guess you probably mean 100MB/s though and that is only what >>the cable can take. >> >>If you take a T-ford onto the highway - can you go 130Km/h in it? >> >>No, the road is rated at 130Km/s but the car can't go that fast. >> >>Same here, the standard says you can transfer 100MB/s over the cable >>but the disk isn't fast enough to be able to transfer that fast. >> >>// Stefan >>-----BEGIN PGP SIGNATURE----- >>Version: GnuPG v1.4.1 (MingW32) >> >>iD8DBQFC5L/BBrn2kJu9P78RAkXKAJ4vc/xQ0Z8mA1ddo79+wC6NCFe5VACgl+j+ >>ceP+as8dx0uZs2W6xaYiMVc=3D >>=3DOf1/ >>-----END PGP SIGNATURE----- >> >> =20 >> >- >To unsubscribe from this list: send the line "unsubscribe linux-ide" i= n >the body of a message to majordomo@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html > > =20 >