From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Evans Subject: Re: 4 partition raid 5 with 2 disks active and 2 spare, how to force? Date: Thu, 25 Mar 2010 20:38:27 -0700 Message-ID: <4877c76c1003252038o655b2a29p9d994df27b5d2afd@mail.gmail.com> References: <2E4545D6-8F4E-4779-9103-960C52983A72@brillgene.com> <4877c76c1003250437r346e18en8da0f6f804bef634@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Anshuman Aggarwal Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Thu, Mar 25, 2010 at 7:09 AM, Anshuman Aggarwal wrote: > Thanks Michael, I am clear about the problem of why the multiple fail= ure would cause me to lose data. Which is why I wanted to consult this = mailing list before proceeding. > > Could you tell me how to keep the array read-only? =A0and mark one or= both of these spares as active forcibly? and Also, once I am able to u= se these spares as active and the data is not consistent in a particula= r stripe, how does the kernel resolve the inconsistency (as in what dat= a does it use, the one based on the data stripes or the one based on th= e parity?) this one is just academic interest since it'll be difficult = to figure out which is the right data anyways. > > Thanks, > Anshuman > Please, read the wikipedia page first, http://en.wikipedia.org/wiki/RAID and then this http://wiki.tldp.org/LVM-on-RAID (some links need updating, but it's still up to date for concepts) With that background nearly out of the way, please stop, and read them both again. Yes, seriously. In order to prevent data loss you'll need to have a good understanding of what RAID does, so that you can watch out for ways it can fail. The next step, before we do /anything/ else is for you to post the COMPLETE output of these commands. mdadm -Dvvs mdadm -Evvs They will help everyone on the list better understand the state of the metadata records and what potential solutions might be possible. -- 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