Re: [gentoo-server] RAID 1+0 question

[Patrick Lauer]

On Wed, 2006-03-01 at 13:40 +0100, Marton Gabor wrote:
> Hi!
>
> I'm going to recieve 4x250Gb SATA disks to our new server, and my first
> idea was to make 2xRAID1 and then make 1xRAID0 out of the RAID1 arrays
> using Linux software raid so that I have our data mirrored and still I
> can use 500Gb storage space and handle it as one big "disk".
> So my questions would be:
>     - could someone give me a good howto? Sorry, but I have never had
> the chance to make a RAID array before and I have no experience and
> Google doesn't seem to be helpful in this case.
>     - do I need to make a /boot partition which is not part of any
> arrays or will grub boot from raid1+0?
grub can boot from raid1, raid0+1 will need a (small) boot partition.

With 4 disks you could also build a raid5 with little overhead, takes a
tad more cpu and gives you 750G capacity (or 500 with one hotspare)

short howto:
Take a livecd with mdadm on it or install an extra harddisk for initial
configuration.
Now you can partition the disks with fdisk.

I'd create a small boot partition and swap partitions (say, 500M per
disk) plus a big partition for "everything". Set the partition type to
FD (?) (raid autodetect)

Maybe you want a smarter setup - use 10G for /, 10G for /var and the
rest for /home or so.
That way you have 10G / raid1, 10G /var raid1 and 240G for /home raid1+0

mdadm is very easy to use.
mdadm --create /dev/md0 /dev/sda1 /dev/sdb1 --level=1 --chunk=128
would create a raid1 (level parameter) with two disks and a chunk size
of 128kB

so just create the devices you need from that - you can delete or change
at any time during the process.

Now you have /dev/md* devices, just format them with the filesystem of
you choice and be happy :-)

if they are type raid autodetect they'll be enabled during boot

Have fun,
Patrick
-- 
Stand still, and let the rest of the universe move