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diff --git a/README_RAID.TXT b/README_RAID.TXT new file mode 100644 index 000000000..38f278287 --- /dev/null +++ b/README_RAID.TXT @@ -0,0 +1,508 @@ +Slackware RAID HOWTO
+
+Version 1.00
+2008/04/29
+
+by Amritpal Bath <amrit@slackware.com>
+
+
+
+Contents
+===============================================================================
+
+- Introduction
+- Warnings
+- Planning
+- Setup
+- Using the generic kernel
+- Troubleshooting
+- Appendices
+- Acknowledgements/References
+
+
+
+
+Introduction
+===============================================================================
+
+This document explains how to install Slackware 13.0 (and beyond) on a
+software RAID root filesystem. It is meant to cover only software raid.
+If you are using a RAID expansion card, or the RAID functionality that came
+with your motherboard, this document will not be useful for you.
+
+In order to follow this document, your computer must have two or more empty
+hard drives. While it is possible to be creative and create RAID arrays on
+drives that already contain data, it can be error prone, so it is not
+covered in this document.
+
+
+
+
+Warnings
+===============================================================================
+
+If you perform the following instructions on hard drives with data on them,
+YOU WILL LOSE ALL OF YOUR DATA.
+
+If you wish to perform these operations on hard drives that hold data of
+any importance, you MUST BACKUP YOUR DATA. The procedure below will
+destroy all of the data on your hard drives, so any important data will
+need to be restored from your backups.
+
+
+
+One more time: *BACKUP YOUR DATA, OR YOU WILL LOSE IT!*
+
+If you don't backup your data and end up losing it, it will be your fault.
+There is nothing I can do to help you in that case.
+
+Now, on with the show... :)
+
+
+
+
+Planning
+===============================================================================
+
+The first step is to determine which RAID level you want to use.
+
+It is recommended that you familiarize yourself with basic RAID concepts,
+such as the various RAID levels that are available to you. You can read
+about these in various places - consult your favorite search engine about
+"raid levels", or see the References section.
+
+Here's a quick summary of the more common RAID levels:
+
+ - RAID 0: Requires 2 drives, can use more. Offers no redundancy, but
+ improves performance by "striping", or interleaving, data between all
+ drives. This RAID level does not help protect your data at all.
+ If you lose one drive, all of your data will be lost.
+
+ - RAID 1: Requires 2 drives, can use more. Offers data redundancy by
+ mirroring data across all drives. This RAID level is the simplest way
+ to protect your data, but is not the most space-efficient method. For
+ example, if you use 3 drives in a RAID 1 array, you gain redundancy, but
+ you still have only 1 disk's worth of space available for use.
+
+ - RAID 5: Requires 3 drives, can use more. Offers data redundancy by
+ storing parity data on each drive. Exactly one disk's worth of space
+ will be used to hold parity data, so while this RAID level is heaviest
+ on the CPU, it is also the most space efficient way of protecting your
+ data. For example, if you use 5 drives to create a RAID 5 array, you
+ will only lose 1 disk's worth of space (unlike RAID 1), so you will
+ end up with 4 disk's worth of space available for use. While simple to
+ setup, this level is not quite as straightforward as setting up RAID 1.
+
+
+
+
+Setup
+===============================================================================
+
+=== Partition hard drives ===
+
+Once you have booted the Slackware installer CD, the first step is to
+partition the hard drives that will be used in the RAID array(s).
+
+I will assume that your first RAID hard drive is /dev/sda. If it is
+/dev/hda or something similar, adjust the following commands appropriately.
+
+You can see your drives by running: cat /proc/partitions
+
+ - /boot: RAID 0 and RAID 5 users will require a separate boot partition, as
+ the computer's BIOS will not understand striped devices. For
+ simplicity's sake, we will make /boot a small RAID 1 (mirror) array.
+ This means that in the case of RAID 0, it will not matter which drive
+ your BIOS attempts to boot, and in the case of RAID 5, losing one drive
+ will not result in losing your /boot partition.
+
+ I recommend at least 30MB for this partition, to give yourself room to
+ play with multiple kernels in the future, should the need arise. I tend
+ to use 100MB, so I can put all sorts of bootable images on the partition,
+ such as MemTest86, for example.
+
+ Go ahead and create a small boot partition now on /dev/sda, via cfdisk
+ (or fdisk, if you prefer).
+
+ Ensure that the partition type is Linux RAID Autodetect (type FD).
+
+
+ - /: Every setup will require a root partition. :) You will likely want to
+ create a partition takes up most of the rest of the drive. Unless you
+ are using LVM (not covered in this document), remember to save some space
+ after this partition for your swap partition! (see below)
+
+ If you are not creating a swap partition, I recommend leaving 100MB of
+ unused space at the end of the drive. (see "safety" for explanation)
+
+ Go ahead and create your main partition now on /dev/sda, via cfdisk
+ (or fdisk, if you prefer).
+
+ Ensure that the partition type is Linux RAID Autodetect (type FD).
+
+
+ - swap: Swap space is where Linux stores data when you're running low on
+ available RAM. For fairly obvious reasons, building this on RAID 0 could
+ be painful (if that array develops a bad sector, for example), so I tend
+ to build swap on RAID 1 as well. If you understand the danger and still
+ want to build swap on RAID 0 to eke out as much performance as possible,
+ go for it.
+
+ For RAID 1 swap, create a partition that is the exact size that you want
+ your swap space to be (for example, 2GB, if you can't decide).
+
+ For RAID 0 swap (not recommended), create a partition that is equivalent
+ to the swap size you want, divided by the number of drives that will be
+ in the array.
+
+ For example, 2GB / 3 drives = 683MB swap partition on /dev/sda.
+
+ Ensure that the partition type is Linux RAID Autodetect (type FD).
+
+ I recommend leaving 100MB of unused space at the end of the drive.
+ (see "safety" for explanation)
+
+ See also: Appendix A - Striping swap space without RAID 0.
+
+
+ - safety! I highly recommend leaving 100MB of unpartitioned space at the
+ end of each drive that will be used in the RAID array(s).
+
+ In the event that you need to replace one of the drives in the array,
+ there is no guarantee that the new drive will be exactly the same size as
+ the drive that you are replacing. For example, even if both drives are
+ 750GB, they may be different revisions or manufacturers, and thus have a
+ size difference of some small number of megabytes.
+
+ This is, however, enough to throw a wrench in your drive-replacement
+ plans - you cannot replace a failed RAID drive with one of a smaller size,
+ for obvious reasons. Having that small 100MB buffer just may save your
+ bacon.
+
+
+
+=== Copy and review partitions ===
+
+Now that /dev/sda is partitioned as appropriate, copy the partitions to all
+the other drives to be used in your RAID arrays.
+
+An easy way to do this is:
+ sfdisk -d /dev/sda | sfdisk /dev/sdb
+
+This will destroy all partitions on /dev/sdb, and replicate /dev/sda's
+partition setup onto it.
+
+After this, your partitions should look something like the following:
+
+ - RAID 0:
+ /dev/sda1 30MB /dev/sdb1 30MB
+ /dev/sda2 100GB /dev/sdb2 100GB
+ /dev/sda3 2GB /dev/sdb3 2GB
+
+ - RAID 1:
+ /dev/sda1 100GB /dev/sdb1 100GB
+ /dev/sda2 2GB /dev/sdb2 2GB
+
+ - RAID 5:
+ /dev/sda1 30MB /dev/sdb1 30MB /dev/sdc1 30MB
+ /dev/sda2 100GB /dev/sdb2 100GB /dev/sdc2 100GB
+ /dev/sda3 2GB /dev/sdb3 2GB /dev/sdc3 2GB
+
+All partition types should be Linux RAID Autodetect (type fd).
+
+
+
+=== Create RAID arrays ===
+
+Now it's time to create the actual RAID arrays based on the partitions that
+were created.
+
+The parameters for each of these RAID commands specifies, in order:
+ - the RAID device node to create (--create /dev/mdX)
+ - the RAID level to use for this array (--level X)
+ - how many devices (partitions) to use in the array (--raid-devices X)
+ - the actual list of devices (/dev/sdaX /dev/sdbX /dev/sdcX)
+
+Start by creating the RAID array for your root filesystem.
+
+ - RAID 0:
+ mdadm --create /dev/md0 --level 0 --raid-devices 2 \
+ /dev/sda2 /dev/sdb2
+
+ - RAID 1:
+ mdadm --create /dev/md0 --level 1 --raid-devices 2 \
+ /dev/sda1 /dev/sdb1
+
+ - RAID 5:
+ mdadm --create /dev/md0 --level 5 --raid-devices 3 \
+ /dev/sda2 /dev/sdb2 /dev/sdc2
+
+
+Next, let's create the array for the swap partition. This will be RAID 1
+regardless of which RAID level your root filesystem uses, but given our
+partition layouts, each command will still be slightly different.
+
+ - RAID 0:
+ mdadm --create /dev/md1 --level 1 --raid-devices 2 \
+ /dev/sda3 /dev/sdb3
+
+ - RAID 1:
+ mdadm --create /dev/md1 --level 1 --raid-devices 2 \
+ /dev/sda2 /dev/sdb2
+
+ - RAID 5:
+ mdadm --create /dev/md1 --level 1 --raid-devices 3 \
+ /dev/sda3 /dev/sdb3 /dev/sdc3
+
+
+Finally, RAID 0 and RAID 5 users will need to create their /boot array.
+RAID 1 users do not need to do this.
+
+ - RAID 0:
+ mdadm --create /dev/md2 --level 1 --raid-devices 2 \
+ /dev/sda1 /dev/sdb1
+
+ - RAID 5:
+ mdadm --create /dev/md2 --level 1 --raid-devices 3 \
+ /dev/sda1 /dev/sdb1 /dev/sdc1
+
+
+We're all done creating our arrays! Yay!
+
+
+
+=== Run Slackware setup ===
+
+First, let's format our swap array, so the installer recognizes it:
+ mkswap /dev/md1
+
+Now run 'setup' as normal.
+
+When you choose to setup your swap partitions, /dev/md1 will show up.
+Continue with this selected.
+
+When asked for the target partition, choose the root array (/dev/md0).
+
+You may choose the format method and filesystem of your choice.
+
+RAID 0 and RAID 5 users must also setup /boot. When asked about setting up
+extra partitions, choose /dev/md2. When asked where to mount this device,
+enter "/boot".
+
+After this, continue installation as normal.
+
+For LILO configuration:
+ - When asked about LILO, choose the "simple" setup.
+ - When asked about additional "append=" parameters, RAID 0 and
+ RAID 5 users should type in "root=/dev/md0", to ensure that the proper
+ array is mounted on / at bootup.
+ - When asked about where to install LILO, choose MBR.
+
+You may see some warnings scroll by. This is OK.
+
+
+
+=== Finishing touches ===
+
+After exiting the installer, we have just a few settings to tweak.
+
+Start by switching into your actual installation directory:
+ - chroot /mnt
+
+
+Let's make sure LILO boots from the RAID arrays properly. Using your
+favorite editor (vim/nano/pico), edit /etc/lilo.conf:
+ - add a new line (add it anywhere, but don't indent it):
+ raid-extra-boot = mbr-only
+ - You will need to change the following line:
+ boot = <something>
+ RAID 0 and RAID 5 users, change it to:
+ boot = /dev/md2
+ RAID 1 users, change it to:
+ boot = /dev/md0
+
+ - Save the file and exit your editor.
+ - run "lilo".
+
+
+When that's done, let's exit the installation and reboot:
+ - exit
+ - reboot
+
+Voila!
+
+
+
+
+Using the generic kernel
+===============================================================================
+
+The official Slackware recommendation is to switch to the "generic"
+Slackware kernel after installation has been completed. If you wish to use
+the generic kernel, you must create an initrd. This section gives a quick
+example of booting a RAID system in this fashion.
+
+If you require more information on initrds, please read /boot/README.initrd.
+
+
+Typically, a user switches to a generic kernel by booting the system, and
+afterwards running the following:
+ - cd /boot
+ - rm vmlinuz System.map config
+ - ln -s vmlinuz-generic-smp-* vmlinuz
+ - ln -s System.map-generic-smp-* System.map
+ - ln -s config-generic-smp-* config
+
+Don't run lilo yet, we'll do that soon.
+
+
+Next, edit (create, if necessary) /etc/mkinitrd.conf and add:
+ MODULE_LIST="ext3"
+ RAID="1"
+
+Obviously, this assumes that you are using the EXT3 filesystem. If you are
+using another filesystem, adjust the module appropriately (reiserfs or xfs,
+for example). If you wish to read more about the MODULE_LIST variable,
+consult "man mkinitrd.conf".
+
+Note: If the module for your hard drive controller is not compiled into the
+generic kernel, you will want to add that module to the MODULE_LIST variable
+in mkinitrd.conf. For example, my controller requires the mptspi module, so
+my /etc/mkinitrd.conf looks like:
+ MODULE_LIST="ext3:mptspi"
+ RAID="1"
+
+
+We're almost done.
+
+Edit /etc/lilo.conf, and find the line at the very end that says:
+ image = /boot/vmlinuz
+Add a new line after it that says:
+ initrd = /boot/initrd.gz
+In this case, be sure to indent the line you've added!
+
+
+Next, create the initrd based on the config file created earlier.
+ mkinitrd -F
+
+
+Finally, run "lilo" to make the new settings take effect, give yourself a
+pat on the back, and reboot your finished system. :)
+
+
+
+
+Troubleshooting
+===============================================================================
+
+Any number of typos can result in a system that does not boot on its own,
+but all is not lost. Put the rubber chicken and the lemon away...
+
+Booting your Slackware media (DVD, for example) can make it very easy to
+switch into your installed system and make repairs:
+
+ - Boot Slackware CD/DVD.
+ - Login to installer as normal.
+ - Scan for, and then assemble the RAID arrays:
+ mdadm -Es > /etc/mdadm.conf
+ mdadm -As
+ - Mount root partition:
+ mount /dev/md0 /mnt
+ - Switch to installed OS:
+ chroot /mnt
+ - Mount remaining filesystems:
+ mount /boot (RAID 0 and RAID 5 users only)
+ mount /proc
+ mount sys /sys -t sysfs
+
+At this point, you can bring up your favorite editor, tweak config files,
+re-run mkinitrd/lilo/etc as you wish, or anything else you need to do to
+make your system bootable again.
+
+When you're finished making your changes, rebooting is simple:
+
+ - cd /
+ - umount boot proc sys
+ - exit
+ - reboot
+
+If you are having issues that you're unable to resolve, shoot me an email.
+Perhaps the answer will make it into this section. :)
+
+
+
+
+Appendices
+===============================================================================
+
+=== Appendix A: Striping swap space without RAID 0 ===
+
+For completeness' sake, I should mention that swap space can be striped to
+improve performance without creating a RAID 0 array.
+
+To accomplish this, start by forgetting about any instructions having to do
+with /dev/md1, which would be our swap array - create the swap partitions on
+the hard drives, but do not create this particular array.
+
+When creating the swap partitions, ensure that the partition type is set to
+Linux Swap (type 82).
+
+During setup, the installer will recognize the swap partitions. Ensure that
+all of them are selected, and continue as normal.
+
+
+After installation is complete, go ahead and boot your system - we can
+finish this once the system is booted, in the interest of simplicity.
+
+
+When the system boots, edit /etc/fstab with your favorite editor. Find the
+lines that describe your swap partitions - they say "swap" in the second
+column.
+
+Each of these lines says "default" in the fourth column. Simply change that
+to "default,pri=0" for each line.
+
+After saving the file, either reboot, or simply run:
+ swapoff -a
+ swapon -a
+
+To confirm that the setting has taken effect, you can run:
+ swapon -s
+
+Verify that the Priority column reads 0 for each partition, and we're done!
+
+
+
+
+Acknowledgements/References
+===============================================================================
+
+- In depth explanation of RAID levels:
+ "LasCon Storage - Different types of RAID"
+ http://www.lascon.co.uk/d008005.htm
+
+- Thanks to John Jenkins (mrgoblin) for some tips in:
+ "Installing with Raid on Slackware 12.0+"
+ http://www.userlocal.com/articles/raid1-slackware-12.php
+
+- Thanks to Karl Magnus Kolstø (karlmag) for his original writeup on
+ Slackware and RAID, ages ago!
+ "INSTALLING SLACKWARE LINUX version 8.1 WITH ROOT PARTITION ON A SOFTWARE
+ RAID level 0 DEVICE"
+ http://www.userlocal.com/articles/raid0-slackware-linux.php
+
+- Of course, thanks to Patrick "The Man" Volkerding for creating Slackware!
+ http://slackware.com/
+
+- Also thanks to the rest of the guys that proofread, tested, and suggested!
+ Eric Hameleers (alienBOB), Robby Workman, Alan Hicks,
+ Piter Punk, Erik Jan Tromp (alphageek)...
+
+- My contact info:
+ Primary email: amrit@slackware.com
+ Secondary email: amrit@transamrit.net
+ On certain IRC networks: "amrit" (or some variation :) )
+
+- This latest version of this document can be found at:
+ http://slackware.com/~amrit/
+ http://transamrit.net/docs/slackware/
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