From mboxrd@z Thu Jan 1 00:00:00 1970 From: Derek Vadala Subject: Re: just how dangerous is this?? Date: Tue, 28 May 2002 17:55:07 -0700 (PDT) Sender: linux-raid-owner@vger.kernel.org Message-ID: References: <20020528215101.E20621@unthought.net> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=X-UNKNOWN Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20020528215101.E20621@unthought.net> To: =?iso-8859-1?Q?Jakob_=D8stergaard?= Cc: Danilo Godec , James Fillman , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Tue, 28 May 2002, [iso-8859-1] Jakob =D8stergaard wrote: > Either it reconstructs it "right" or it does it "wrong". It seems in > his case it did it right. Lucky him. >=20 > Hoever, the persistent superblocks will overwrite the last few KB of = his > *filesystem* on each partition. So things *may* seem to work, but t= he > system will fail horribly later. After an fsck the RAID suprblocks w= ill > be damaged. After another mkraid the filesystem will be damaged agai= n. You should be able to pre-plan by creating initial ext2 file systems th= at are smaller than the partition size. You can do this by specifying the number of blocks in the file system when you run mke2fs.=20 mke2fs [options] device blocks You should be able to calculate the eventual location of the md superbl= ock and select an appropriate block size for each partition to insure that = the superlbock and the filesystem do not overlap.=20 Even if you've had sucess thus far, it's likely that problems will aris= e as the filesystem fills up-- when the last blocks are allocated, and th= ey overlap the md superblock. This probably isn't worth the effort unless you are doing multiple installs with the same partition layout and hardware, but it seems that= it might be the case here. I think the formula should be something like: blocks - (blocks % 64) - 64 =3D md offset That's for 1k blocks... ( like from fdisk -l) I'm a bit lazy to double check, but I think that formula works. Then when creating a filesystem divide by block size and create a file system that's the right size...=20 --- Derek Vadala, derek@cynicism.com, http://www.cynicism.com/~derek - 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