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 13:37:34 -0800 Sender: linux-raid-owner@vger.kernel.org Message-ID: <006501c27eca$3a1f0440$707ba8c0@YQDING> References: <20021022104522.GC24075@unthought.net> <20021022112401.GA26549@unthought.net> <004e01c27eaf$b6c11940$707ba8c0@YQDING> <20021028210240.GB15779@unthought.net> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: To: Jakob Oestergaard Cc: raid@ddx.a2000.nu, linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi Jakob, I don't follow your guesses. Why do you think it may be related to chun= k size? Anyway, I'm using 32K. yq ----- Original Message ----- =46rom: "Jakob Oestergaard" To: "Yiqiang Ding" Cc: ; Sent: Monday, October 28, 2002 1:02 PM Subject: Re: Is Read speed faster when 1 disk is failed on raid5 ? > On Mon, Oct 28, 2002 at 10:27:46AM -0800, Yiqiang Ding wrote: > > I had the similar result with IDE drives through hpt374 controller. Still > > don't understand why a degraded system has better read performance. > > Could you comment on the guesses I made below, relating to the chunk > size? > > > > Other than that... Well, if the parity information is intact, the disks > > > would need to skip the parity blocks when the array is read from > > > sequentially. With a degraded array, the reads are all contiguou= s 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 last > > > guess holds), then try 128k. If you are using 64k or above (whic= h, > > > 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