Dnia 2010-01-27, śro o godzinie 09:26 -0500, Carlos Williams pisze:

I am building a Linux system which has 4 identical 'fd' partitions on
each of the 4 drives. I don't want to use the 4th partition or disk if
you would like to call it as a 'hot spare'. I would like to span the
entire array over the 4 drives. My question is does my command look
correct for doing so?

I'm not sure I understand what you want to achieve. A 'spare' disk is
one that isn't used until any of the other fail, then the spare replaces
the failed one. The term 'hot spare' is used to identify a disk that is
a mirror of one of the other drives, but there's no support for that in
Linux Software-RAID.

mdadm --create /dev/md0 --level=5 --raid-devices=4 /dev/sda2 /dev/sdb2
/dev/sdc2 /dev/sdd2 

This will create a RAID5 array of 4 devices, yes. Capacity will be 3 x
sd?2. Failure of any one of those disks will not harm the data.

-- 
Cheers
Michał (Saviq) Sawicz