Ok, I give up... I have to ask. This is CentOS 5. I switched one of my raid1 disks, and I already thought I had succeeded. But now it seems that something is very wrong with the first partition on the new disk. Luckily my system is fully bootable with the other disk. Here's some info. The new disk is sdb. // I removed all partitions with parted, and created the first one again. // parted does not complain: [root at mail dev]# parted sdb Using /dev/sdb (parted) print Model: ATA SAMSUNG HD321KJ (scsi) Disk /dev/sdb: 320GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 1 0.51kB 101MB 101MB primary ext2 (parted) rm 1 (parted) mkpart primary 1 100 (parted) print Model: ATA SAMSUNG HD321KJ (scsi) Disk /dev/sdb: 320GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 1 0.51kB 100MB 100MB primary ext2 (parted) quit // If I try to create a file system on the new partition, // I get an error message: [root at mail dev]# mkfs ext3 sdb1 mke2fs 1.39 (29-May-2006) mkfs.ext2: invalid blocks count - sdb1 // I cannot create a volume label: [root at mail dev]# e2label sdb1 /mnt/mirror [root at mail dev]# e2label sdb1 [root at mail dev]# //fsck informs me like this: [root at mail dev]# e2fsck sdb1 e2fsck 1.39 (29-May-2006) The filesystem size (according to the superblock) is 77392578 blocks The physical size of the device is 24414 blocks Either the superblock or the partition table is likely to be corrupt! Abort<y>? yes // I even tried fsck using the secondary (or tertiary) superblock // but no success. So now what? Apart from doing a low-level format. - Jussi -- Jussi Hirvi * Green Spot Topeliuksenkatu 15 C * 00250 Helsinki * Finland Tel. & fax +358 9 493 981 * Mobile +358 40 771 2098 (only sms) jussi.hirvi at greenspot.fi * http://www.greenspot.fi