>If you are using hardware RAID devices, do not attempt to run software RAIDs on top of it.
>why is this so?
Probably because SuSE's system boot-up scripts cannot handle such a combination.
Notice that the document is about configuring the _root_ partition: it must be activated very early in the boot-up sequence, using the limited set of utilities available within the initrd file. Because of that, the root filesystem configuration may have some limitations that won't apply to other filesystems.
> when it comes to hardware RAID devices,(say a bunch of HDDs with hardware RAID1 or RAID5) is there anything different we have to do when partitioning from OS level?
With hardware RAID, you must first configure the RAID controller, or the system won't see the disks connected to the RAID controller at all. This is usually done either by accessing the RAID controller's BIOS menu by pressing a key _when prompted_ when the system is booting (typically key F8 on Proliant hardware), or using a configuration program on a bootable CD-ROM (SmartStart CD on Proliant hardware).
Usually the actual disks are called "physical disks", and the RAID sets built from them are called "logical disks" in the RAID controller configuration.
(Note: if you use LVM, what is called a "logical disk" by the RAID controller may be used as a "physical volume" by the LVM.)
On Linux, you normally expect your disks to be named like /dev/sdX, where X is a letter (or two or more letters if you have a lot of disks). On Proliant hardware, the SmartArray hardware RAID controllers use different names: SmartArray-connected disks are named like /dev/cciss/cXdY, where X is the number of the SmartArray controller, and Y is the number of configured logical disk. When a SmartArray disk is partitioned, the partitions are accessible as /dev/cciss/cXdYpZ, where Z is the partition number.
(Very old SmartArray controllers had another naming scheme: /dev/ida/cXdY and /dev/ida/cXdYpZ respectively. But all those controllers should be at least 10 years old now.)
Some hardware RAID controllers (like LSI Logic Megaraid) use the standard Linux /dev/sdX names for disks.
Other than the requirement to configure the RAID controller first, and maybe a different naming scheme, the partitioning of a hardware RAID logical disk should be no different than partitioning a single stand-alone disk.
If your OS installer sees no disks even though your RAID controller is configured, you might need an updated driver. For example, the cciss driver covers practically all modern SmartArray RAID controllers (except SmartArray B110i, see below), but it might not be able to recognize SmartArray models that are newer than the driver version. The old driver obviously can't know about hardware models that didn't exist when that driver version was created!
HP offers "driver disks" for some Linux distributions. These are newer versions of the RAID driver, packaged in a format that can be read by the distribution's installer. Although they are called "driver disks", in these days you can usually supply them to the installer using an USB stick too. For details, see the installation instructions of your Linux distribution.
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Note: some of the very low-end Proliant servers currently have a disk controller that is called "SmartArray B110i". Although it's disk-format compatible with bigger SmartArray models, the B110i is *not* a true hardware RAID.
Unless a special hpahcisr driver is installed, the B110i is detected as a simple AHCI SATA controller, using the AHCI driver that is built into most modern Linux distributions. The AHCI driver won't understand SmartArray disk metadata: only the special hpahcisr driver can do that.
If you have a SmartArray B110i, read the installation instructions in the server documentation *very* carefully, and never update your Linux kernel without first checking that your hpahcisr driver version is compatible with the updated kernel version.
MK
MK
