question about md devices and kickstart config file

[Aleksandar Milivojevic]

Say I have one disk in machine, but plan on adding second disk and doing 
mirroring some time after the initial install.

No problem, it is kind of possible to add mirroring afterwards.

However, is it possible to configure md devices on the first (single 
disk) and than simply add second disk?

The first idea was to create mirror in degraded mode, and have it 
running in degraded mode until second disk is installed.  I believe that 
currently it is not possible to create RAID1 device with second disk 
missing.  This is stupid limitation, but OK, that's how things are for 
now (on every other software RAID implementation I used to work with, it 
was possible to create mirrors in degraded mode, sigh).

Another idea was creating RAID0 or linear device with only one disk 
(since it would have only one device, data would be organized the same 
as if it was mirror), and than reconfiguring it to RAID1 device later. 
Has anybody attempted this?  First, is it possible to created RAID0 or 
linear device with only one disk?  Second, is it possible to reconfigure 
the device to RAID1 without loss of data?

The last idea was going with normal partitions (no md devices) but 
configuring everything not to use the last block (that will be used for 
md superblock).  This would eliminate the "resize filesystem" step when 
converting to RAID1.  If I understood correctly, md device will use last 
block (512 bytes physical disc block?) of partition.  Is it possible to 
specify in ks.cfg file that file system created on the partition should 
be shorter for one block?  What about LVM, is it possible to tell it not 
to use last block of physical partition?

-- 
Aleksandar Milivojevic <amilivojevic at pbl.ca>    Pollard Banknote Limited
Systems Administrator                           1499 Buffalo Place
Tel: (204) 474-2323 ext 276                     Winnipeg, MB  R3T 1L7