convert legacy array in place?

Hi,

It seems like this should be a FAQ but careful google and mailing list archive searches didn't seem to turn up anything.

I have two machines with legacy RAID-0 arrays created with raidtools. I have updated one to Fedora Core 4 and now use mdadm. Am I correct in thinking I have to use "mdadm --build" every boot to access the array? My mdadm.conf contains

DEVICES /dev/hda1 /dev/hdb1 /dev/hdc1
ARRAY /dev/md0 level=raid0 num-devices=3 devices=/dev/hda1,/dev/hdb1,/dev/hdc1

but the array doesn't seem to come up by itself on boot.

On the same lines, can this array be converted to a new style array just by writing new superblocks, or do I have to do the backup-reformat-restore thing?

TIA.

If it is a "legacy array" in that it was created with "persisent-superblock = no"
then you are right. You need to use "mdadm --build" to assemble it. --assemble ONLY works with arrays that have superblocks. With --build, you need to make sure that you get the chunksize correct of course (as it isn't stored in the superblock).

An array with superblocks is slightly smaller than the legacy array (due to the superblocks). So you cannot do a straight conversion. If you have afford to loose the last 64k-per-device of the array, then you can simply re-create it as a with-superblock array.

If you are using ext2 or ext3, then you may be able to resize you filesystem down with resize2fs and then remake the array.

NeilBrown