[CentOS] Manual Paritioning with fdisk
dan1
dan1 at edenpics.com
Tue Apr 12 04:19:52 UTC 2005
Hello, Gerald.
This is my personnal step by step documentation about how to install
software RAID with CentOS 3 or 4.
---------------------------
The easiest way to setup a software RAID filesystem is to create it at
install time, when you install your RHEL with the CDs.
When you come to the partitionning section of the installation at the
beginning, you will be able to choose 'Disk Druid' to partition your disks.
Choose this one and follow these steps:
1. Create your partitions as you normally do on the first disk. However, use
the 'Software RAID' filesystem type instead of ext3. It's at the RAID level
that you will specify the ext3 filesystem later. For the /boot partition,
put it first and choose 'set as primary', because else disk druid will
change it's order.
2. Once /boot, / and a swap partition (minimum) have been created, you must
copy this partition information on the second drive, because the two disks
must be identical. To do that, click on the 'RAID' button and choose 'clone
drive'. Else you can just do exactly the same things that you did on the
first drive to the second drive, it works fine also. I suggest you put 100Mb
for /boot, and twice the RAM memory you have for the swap partition.
3. Create the software raid partitions, by clicking on 'RAID' and then
'create a RAID device like /dev/md0'. Once there, you have to choose which
partitions to include to the mount point that you will specify.
Here is the recommended method:
- /boot = /dev/md0 (always 100Mb)
- swap = /dev/md1 (between 1 to 4 Gb)
- / = /dev/md2 (rest of the disk)
Also, choose the 'ext3' filesystem instead of 'ext2', which is much more
reliable even if a little bit slower. Put the swap partition just after the
boot partition, because then you should theoretically win some speed
performance because it will be a short way between the swap and the RHEL
root files installation (if you have hundreds of Gb on the root partition
and you put the swap partition after that, then you might loose each time
the whole length of the disk to seek the datas and this might be much
longer..).
Choose the RAID level you wish for each partition. RAID 0 is striped
(doubles volume but no redundancy). RAID 1 is mirroring. It has redudancy
and accelerates the read time. This is a very good level. RAID 5 needs at
least 3 disks.
Also, choose the RAID members for this RAID partition. You should put the
correspondig partition for each disk hda and hdb only. This means that you
will check only two partitions, one for each drive.
Once this is done, you can continue with the installation process. At the
end, you will still have to make your second disk be bootable and save the
partitions (see further on).
---------------------------
As for how to make both boot partitions boot so that if one of both disks
fails the system would still boot up, this is my note about it, but works
only for CentOS 3. On CentOS 4 I have no idea:
raidstop /dev/md0
fdisk /dev/hda
type 't' and then '1' for boot partition, and then 'fd' for the Linux raid
autodetect filesystem, and finally 'w' to save changes to the disk and quit.
Do the same with the second disk of the array.
Hope this helps.
Daniel
----- Original Message -----
From: Gerald Waugh
To: CentOS mailing list
Sent: Tuesday, April 12, 2005 12:34 AM
Subject: Re: [CentOS] Manual Paritioning with fdisk
On Mon, 2005-04-11 at 17:20 -0500, Les Mikesell wrote:
> Won't such a machine crash when one of the drives containing swapped-out
> data dies?
Yep!
swap must be mirrored.
For the life of me I can't get disk druid to create RAID partitions
properly
Could someone give me a step-by-step ;) Please!
Gerald
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