From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Janos Haar" Subject: questions about softraid limitations Date: Wed, 14 May 2008 02:34:19 +0200 Message-ID: <002801c8b55a$60e4a360$0404a8c0@dcccs> Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-2"; reply-type=original Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hello list, Neil, I have worked on a faulty hw raid card data recovery some days before. The project is already successfully done, but i run into some limitations. For the best safe way first i have jumperd the drives to readonly mode. Than try to build an "old fashion" linear arrays from each disks + 64k another blockdevice. (for store the superblock) But the mdadm refused to _build_ the array, because the source scsi drive is jumpered to readonly. Why? :-) I try to build the array with --readonly option, but the mdadm still dont understand what i want. (yes, i know, rtfm...) The next step is: mdadm --create --assume-clean -l 5 /dev/mdX --raid-disks 5 /dev/.... (And this step is refused too if the drives or some part of the sources are readonly.) Its OK, but what about building a readonly raid 5 array for recovery usage only? :-) And _build_ a degraded-readonly raid 4-5-6 is even better if this will ever available.... And i need to set the readonly flag _after_ the --create, but the --create + --assume-clean is logical, and working combination with --readonly. More additionally, i think the only write the superblocks to the disks, when the --readonly flag is cleared. And more, if the readonly raid 4-5-6 array can handle, and recover the bad sectors from the parity infos.... hmmmm... :-) These little options can be great help for data recovery, and all is safe. Thanks and regards, Janos Haar