LSILogic controllers are supported by themegaraidkernel driver, which is found in the SCSI low-level drivers configuration submenu:
SCSI support --->
SCSI low-level drivers --->
...
<*> AMI MegaRAID support ...
There are no other configurable kernel options for themegaraid driver.
Converting an Existing Standalone Disk to a Mirror
Follow these steps if you want to replace your existing disk controller with an LSI Logic RAID controller and mirror your existing system disk.
1. Before physically replacing the controller, configure a new kernel with support for themegaraiddriver. After the kernel is compiled, install it and add an/etc/
lilo.conf stanza for it. Don’t forget to run /sbin/lilo to rebuild the master boot record, too.
2. Power down the system and install the new controller in place of your original disk controller. Connect your existing disk and any new disks to the new LSI Logic RAID adapter.
3. After powering on the system, useCTRL-Mto enter the MegaRAID Configuration Utility. (You can, alternatively, use the WebBIOS tool to perform the steps I have outlined here. However, I’m going to provide step-by-step instructions for the MegaRAID Configuration Utility because it’s usable by everyone and is a bit more obtuse.)
4. Choose Configure and then New Configuration from the main menu. A list of disks, organized by channel, is presented. Use the arrow keys to move between disks and theSPACEBARto include a disk in the array. Select your original system disk first and then the new disk. Once a disk is selected, it will be marked online.
5. Press theENTER key twice, and a window containing RAID properties appears.
Make certain that RAID-1 is selected, and tune the other options to you meet your needs.
6. Choose Accept (you will need to press theENTERkey twice) and a final confirma-tion dialog appears. Answer yes, and the configuraconfirma-tion is written into the con-troller’s memory.
7. At the main menu, choose Check Consistency. Use the SPACEBAR to select the array you just created and pressF10to begin the consistency check. The process could take some time, but when it is complete, your RAID-1 will be operational.
Then reboot the system and run Linux as you would normally.
Managing Arrays
Like many other hardware vendors, LSILogic does not provide a way to manage arrays from within Linux. Dell has ported the MS-DOS version of the MegaRAID Configuration Utility to Linux, but if you use it, don’t expect support from LSILogic or Dell. Since Dell only uses certain LSILogic controllers in its servers, you might experience varied results when using Dell’s MegaRAID management utility. I recom-mend searching the Web to read about other users’ experiences with the controller you purchased to find out if an undocumented bug destroys the information on your disks, or worse.
Download the utility from Matt Domsch’s Linux web page (http://www.domsch.com/
linux/). Using the utility is very straightforward; it’s a statically compiled binary and works the same as the BIOS utility.
Chapter 6
CHAPTER 6
Filesystems
Choosing and properly configuring a filesystem is as important as selecting an appro-priate RAID level.ext2(the Second Extended Filesystem) is the standard Linux filesys-tem. Many users will be perfectly happy using ext2; it is reliable and can be fine-tuned to meet specific demands of file usage. But while ext2 might be suitable for end users, it doesn’t fare as well for large, heavily used filesystems that have extremely large files or thousands of small files. ext2 doesn’t provide any way to maintain filesystem integrity through system crashes. Also, ext2 is slowly making way forext3, a journaling filesystem that I’ll cover later in this chapter. Maintaining data integrity and availability has become an essential requirement for all critical sys-tems. After all, this is one of the most recognizable benefits of RAID. Fortunately, there are a wide variety of filesystems for Linux that implement crash recovery and prevention features. These systems are collectively called journaling filesystems, and their main distinction from traditional Unix filesystems is that they don’t require file-system checks after a file-system crash. I’ll cover journaling in greater detail later in this chapter. Even if you aren’t interested in journaling filesystems right now, it’s a good idea to begin learning about them. It won’t be long before your need for increased data reliability or fast recovery may force you to make a change to a journaling file-system.
There are several alternatives to ext2, in the event that it does not meet your needs.
IBM has ported its JFS implementation to Linux. (Like many computer industry terms, JFS has a dual meaning. It refers generically to any journaling filesystem, but also refers specifically to the IBM implementation.) Silicon Graphics has released XFS, the longtime journaling filesystem of the IRIX platform, for Linux. And Hans Reiser has createdReiserFS, a journaling filesystem developed specifically for Linux.
Finally, ext3 enhances the features of ext2 by adding journaling capabilities, along with many other features.
This chapter includes information about each of these filesystems, but a complete primer on the different filesystems is well beyond the scope of this book. Ihave pro-vided enough information here so that you can make an informed decision about
which filesystem to choose, how to patch your kernel, and how to build the filesys-tem. Istrongly recommend reading more about each of the filesystems at their respective web sites (for which I’ve provided references).
Each of the filesystems that Icover in this chapter, including ext2, can be fine-tuned using filesystem parameters and mount options. In this chapter, I will explain how to make some adjustments that will improve overall system performance.