From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Yiqiang Ding" Subject: Re: Is Read speed faster when 1 disk is failed on raid5 ? Date: Mon, 28 Oct 2002 10:27:46 -0800 Sender: linux-raid-owner@vger.kernel.org Message-ID: <004e01c27eaf$b6c11940$707ba8c0@YQDING> References: <20021022104522.GC24075@unthought.net> <20021022112401.GA26549@unthought.net> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: To: Jakob Oestergaard , raid@ddx.a2000.nu Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids I had the similar result with IDE drives through hpt374 controller. Sti= ll don't understand why a degraded system has better read performance. YQ ----- Original Message ----- =46rom: "Jakob Oestergaard" To: Cc: Sent: Tuesday, October 22, 2002 3:24 AM Subject: Re: Is Read speed faster when 1 disk is failed on raid5 ? > On Tue, Oct 22, 2002 at 12:49:41PM +0200, raid@ddx.a2000.nu wrote: > > > > On Tue, 22 Oct 2002, Jakob Oestergaard wrote: > > > > > I didn't follow the beginning of this thread, sorry. Is this SCS= I? > > > > Ide disks on 3ware 7850 using software raid5 > > Ok. Odd. > > My first guess would be that it's some master/slave IDE issue - but y= ou > are probably running all your disks as masters (one disk per channel)= , > right? > > Other than that... Well, if the parity information is intact, the dis= ks > would need to skip the parity blocks when the array is read from > sequentially. With a degraded array, the reads are all contiguous on > the disks - this could be a difference perhaps?? > > What chunk size are you using? And can you try a chunk size that is = an > order of magnitude bigger or smaller? (might take some time to test > this out). > > For example, if you use a 4k chunksize (I don't think you do, if my l= ast > guess holds), then try 128k. If you are using 64k or above (which, > again, if I am guessing correctly, is probably more like what you're > using), then try 4k. > > -- > ................................................................ > : jakob@unthought.net : And I see the elder races, : > :.........................: putrid forms of man : > : Jakob =D8stergaard : See him rise and claim the earth, : > : OZ9ABN : his downfall is at hand. : > :.........................:............{Konkhra}...............: > - > To unsubscribe from this list: send the line "unsubscribe linux-raid"= in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > > - 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