[kwlug-disc] RAID-0 for the first time

Richard Weait richard at weait.com
Wed Feb 24 22:18:55 EST 2010

I'm playing with RAID-0 for the first time.  There are three disk
drives; one (500GB) for Operating system and everyday stuff, and two
additional identical drives for RAID-y stuff.

The OS is installed and working fine, thanks for asking.  ;-)

For the RAID-0, it might actually be installed and working properly,
but df -hT reports too much capacity on the RAID drive.  In fact it
reports roughly the sum of the capacity of the two RAID drives.  I was
expecting roughly the capacity of one of the identical RAID drives to
be reported as the capacity of the RAID-0 array.

I set it up like this

Partition two drives
- each of the two (sde, sdf) were partitioned (fdisk) with a single
partition, primary, 1, all sectors.
- and a type of Linux raid auto (df)

Create RAID-0 from two partitions
sudo mdadm --create /dev/md0 --level=0 --raid-devices=2 /dev/sde1 /dev/sdf1

Add filesystem to RAID-0
sudo mke2fs -j /dev/md0

Make a mount point for it
sudo mkdir /raid

Mount it
sudo mount /dev/md0 /raid

But df thinks the RAID-0 drive is too big.
df -hT
Filesystem    Type    Size  Used Avail Use% Mounted on
/dev/sdg1     ext4    440G  6.0G  412G   2% /
/dev/md0      ext3    1.8T  196M  1.7T   1% /raid

Wazzup with that?  Does df just not get RAID, or did I hose the RAID setup?

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