On 4 February 2011 00:31, Jon Forrest <jlforrest@xxxxxxxxxxxx> wrote: > (I see that other people have had this problem > but not in the same situation as me. Mine > is probably as simple as you can get). > > I'm learning about how to manage software raid > by using loopback devices on a RHEL6 system > (2.6.32-71.14.1.el6.i686). > > I create two loopback devices thusly: > > # dd if=/dev/zero of=file0 bs=1k count=100 > 100+0 records in > 100+0 records out > 102400 bytes (102 kB) copied, 0.000689998 s, 148 MB/s > # cp file0 file1 > # losetup /dev/loop0 file0 > # losetup /dev/loop1 file1 > > I can create a RAID1 volume with no problems: > > # mdadm --create /dev/md0 --raid-device=2 --level=1 /dev/loop0 /dev/loop1 > mdadm: Defaulting to version 1.2 metadata > mdadm: array /dev/md0 started. > > However, doing the same thing but creating a RAID0 volume > fails thusly: > > # dd if=/dev/zero of=file2 bs=1k count=100 > 100+0 records in > 100+0 records out > 102400 bytes (102 kB) copied, 0.000699377 s, 146 MB/s > # cp file2 file3 > # losetup /dev/loop2 file2 > # losetup /dev/loop3 file3 > # mdadm --create /dev/md1 --raid-device=2 --level=0 /dev/loop2 /dev/loop3 > mdadm: Defaulting to version 1.2 metadata > mdadm: ADD_NEW_DISK for /dev/loop2 failed: Invalid argument > > I don't understand what went wrong? Any ideas? > > Cordially, > -- > Jon Forrest > Research Computing Support > College of Chemistry > 173 Tan Hall > University of California Berkeley > Berkeley, CA > 94720-1460 > 510-643-1032 > jlforrest@xxxxxxxxxxxx > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at Âhttp://vger.kernel.org/majordomo-info.html > I just tried this on Ubuntu 10.10 and I got this: sudo mdadm --create /dev/md0 --raid-device=2 --level=1 /dev/loop0 /dev/loop1 mdadm: /dev/loop0 is too small: 100K mdadm: /dev/loop1 is too small: 100K mdadm: create aborted mdadm - v2.6.7.1 - 15th October 2008 2.6.35-26-generic // Mathias -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
