Swap Space In A Raid Configuration; Boot Partitions In A Mirrored Raid Configuration - HP xw3400 User Manual

Chunk sizes must be specified for all RAID levels, including linear mode. However, the chunk size
does not make any difference for RAID-Linear. The argument to the chunk-size option in the
/etc/raidtab file specifies the chunk size in kB, so "4" means "4kB."
For optimal performance, you should experiment with the value, as well as with the block-size of the
filesystem you put in the array.

Swap Space in a RAID Configuration

There is generally no need to use RAID for swap performance. The kernel itself can stripe the swap
space over multiple physical disks, provided each stripe is given the same priority in the
/etc/fstab file. For example, the /etc/fstab file for striping the swap space over three drives
might look like the following:
/dev/sda2
/dev/sdb2
/dev/sdc2
This will allow the machine to swap in parallel over multiple physical devices. The Linux kernel itself
has this capability; there is no need for RAID implementation of swap space.

Boot Partitions in a Mirrored RAID Configuration

The mirroring for Linux in software RAID configuration is the mirroring of partitions, not physical
drives. For this reason, the Master Boot Record (MBR) is not mirrored in a RAID-1 configuration, and
therefore, the mirrored drive or drives are not inherently bootable. Currently there is no way to mirror
the boot partition of a hard drive using utilities such as Disk Druid, so the mirrored drives must be
configured manually in order to make them bootable by Linux in case the first drive fails.
One possible configuration for a software RAID-1 array in Linux is to install the /boot partition on a
separate physical hard disk from the rest of the filesystem. For example, /dev/sda1 would be a
hard disk containing the /boot partition, and /dev/sdb1 and /dev/sdc1 would be separate
physical disks making up the / partition, configured in a RAID-1 array that is independent of the
/boot partition. In this case, failure of one of the hard disks in the RAID array would not affect the
disk with the /boot partition.
If placing the / and /boot partitions on separate physical drives as described above is not possible
or desirable, more manual configuration is required to make sure that all hard drives in a RAID-1
array will be bootable in case of failure. In this case, you will need to create a bootable partition on
each physical hard disk that will be part of the RAID-1 array. This is easiest when done during the
original installation and configuration of the Linux workstation.
The steps to manually mirror your boot partition are outlined below:
1. Power your HP workstation; boot to your RHEL installation media.
2. Continue through the installation until the "Disk Partitioning Setup" screen.
3. Select "Manually partition with Disk Druid."
swap swap
swap swap
swap swap
defaults,pri=1 0 0
defaults,pri=1 0 0
defaults,pri=1 0 0
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