Following this note is a draft of a "Mirrored Linux Mini How-to" document.
It's primarily for my own use, but I will make it available to anyone who
would like a copy.
Before I do this, I would like input from this group as to whether it:
1. is a good idea?
2. has no obvious errors or problems?
3. will reliably work?
4. Should I provide more details? Or at least pointers to using fdisk, etc.
Thanks for the assistance
Harold
==============================================================================
Mirrored Linux Mini How-to
Install linux on two identical disk drives in such a way that the failure
of either of the drives will allow the system to be recovered without any
loss of data
Both of the drives are partitioned exactly the same:
1. 3 primary partitions
2. Partition 1 - size - 1GB format as Linux Raid (fd)
3. Partition 2 - size = real memory size, format as linux swap (82)
4. Partition 3 = size = remainder of disk, format as linux raid (fd)
To ensure that the partitions are correct, and in the correct order, boot from
the install CD/DVD and run the rescue system. Use fdisk from this system
to partition the two drives. (The GUI disk partitioner which runs in the
anaconda installer has a tendency to move partitions around without asking.
We don't want this to happen!) After saving the partition information on
both drives, you can Run the Linux installer. Select "custom" installation.
Define a raid 1 mirror named fd0 using the first partition on both drives
Define a raid 1 mirror named fd1 using the third partition of both drives
Define a linux ext3 filesystem on fd0. Mount on /boot
Define a linux Logical Volume Group named vg0 on fd1.
Within vg0, define the following Logical Volumes:
lv00 - /
lv01 - /tmp
lv02 - /var
lv03 - /usr
lv04 - /usr/local
lv05 - /home
lv06 - /opt
I'm from the old school. I believe in lots of partitions. Create any
additional partitions you may need. If you really want to, you can
just create a single partition and put "/" in it. You still will
need the "/boot" partition since you can't boot from an LVM partition.
You can now continue to install linux normally. I usually do it twice.
the first time is to get an idea of how big each partition should be
and the second time is to get it right. Remember to leave some extra
unallocated space in the volume group to be allocated later if one of your
file systems fills up. Read the linux logical volume manager docs.
In the event of a disk failure, follow the below procedure.
1. Shutdown the system and remove the failed drive.
2. If the second (non boot) drive is the failing drive, skip to step 9 below.
3. Move the second (non boot) drive to the boot drive position.
4. Boot from the linux rescue CD/DVD and start the system, no network.
5. Use the "chroot /mnt/sysimage" command to mount the system.
6. Run the command "/sbin/grub-install /dev/sda" or whatever your drive is
to write a boot image into the MBR of the new boot drive.
7. Remove the CD/DVD and re-boot. The system should boot on a single drive
and both raid array's will show no spare available.
8. Shutdown the system
9. Install a new drive, identical to the existing drive if possible.
10. Bring up the system and use fdisk to partition the new drive EXACTLY
the same as the existing drive.
11. Format the swap partition with "mkswap /dev/sdb2"
12. Add the mirror for the /boot partition with "mdadm --add /dev/md0 /dev/sdb1"
or whatever is appropriate for your system...
13. Add the mirror for the LVM partition with "mdadm --add /dev/md1 /dev/sdb3"
or whatever is appropriate for your system...
14. Wait for the mirror to sync. It may take several hours
------------------------------------------------------------------------------
Example:
Disk /dev/sda: 200.0 GB, 200049647616 bytes
255 heads, 63 sectors/track, 24321 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 131 1052226 fd Linux raid autodetect
/dev/sda2 132 392 2096482+ 82 Linux swap / Solaris
/dev/sda3 393 24321 192209692+ fd Linux raid autodetect
/dev/sdb is exactly the same
md0 : active raid1 sdb1[1] sda1[0]
1052160 blocks [2/2] [UU]
md1 : active raid1 sdb3[1] sda3[0]
192209600 blocks [2/2] [UU]
Filesystem Size Used Avail Use% Mounted on
/dev/md0 996M 52M 893M 6% /boot
/dev/mapper/vg0-lv00 992M 373M 568M 40% /
/dev/mapper/vg0-lv01 2.0G 101M 1.8G 6% /tmp
/dev/mapper/vg0-lv02 2.0G 266M 1.6G 15% /var
/dev/mapper/vg0-lv03 4.9G 2.8G 1.9G 60% /usr
/dev/mapper/vg0-lv04 992M 104M 837M 12% /usr/local
/dev/mapper/vg0-lv05 2.0G 132M 1.8G 7% /var/www
/dev/mapper/vg0-lv06 20G 6.6G 12G 36% /home
/dev/mapper/vg0-lv07 44G 39G 3.2G 93% /opt
tmpfs 1010M 0 1010M 0% /dev/shm
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