From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roberto Spadim Subject: Re: raid1 mirror optimizations Date: Wed, 26 Jan 2011 12:18:02 -0200 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: David Brown Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids nice :) i never read about it on raid 10, maybe i could use, thanks! 2011/1/26 David Brown : > On 25/01/2011 19:56, Roberto Spadim wrote: >> >> hi guys... i have a damaged disk... >> i=E6=83=B4 using raid1 >> the computer crashed with the floor :P hihiih sorry, but the disks a= re >> damaged at the same position >> check: http://www.spadim.com.br/hd%20agra.zip >> the problem: since raid1 (mirror) is done with real mirror, the disk >> position are the same... >> if i was using a mirror but on disk 1 i write from beggining to end, >> and disk 2 from end to beggining , i don=E6=84=92 crash the disk at = the same >> position, for disk 1 i crash it some bytes, for disk 2 i crash some >> others bytes, since beggining is a small cilinder and end a bigger, = i >> could loose less information than mirror >> could we implement a 'inverted' mirror? just for hard disks (for ssd >> it=E6=84=80 a small loss of cpu/memory) >> thanks >> > > If you are worried about the disks being in the same position, then I= assume > you mean the heads were in the same position when they crashed into t= he > disk. =C2=A0If that's the case, then it doesn't really matter too muc= h if the > same bytes on the disk were hit - your disks are trashed anyway, and = you'll > need expensive professional recovery services to deal with it. > > If you are not talking about head crashes, and merely about corruptio= n > because the disks were being written to in the same place on both dis= ks, > then the layout on the disk will make little difference - the same da= ta will > be written to the same logical place at roughly the same time. =C2=A0= It doesn't > matter where this data is located physically on the disk, since it is= the > data that matters. =C2=A0The same thing actually applies to head cras= hes too. > > If you really want an "inverted" mirror, there is an easy way to get = much of > the same effect. =C2=A0Instead of setting up raid1, use raid10 with "= far 2" > positioning. =C2=A0The effect is roughly like this: > > disk1 (stripe 1) (mirror of stripe 2) > disk2 (stripe 2) (mirror of stripe 1) > > So the two copies of the data are in different physical positions on = each > disk. =C2=A0It's not a full reversal, but you can think of disk 2 as = being split > in two and its two halves swapped. > > > -- > 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 =C2=A0http://vger.kernel.org/majordomo-info.ht= ml > --=20 Roberto Spadim Spadim Technology / SPAEmpresarial -- 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