Linux RAID Guide


	Linux RAID Guide Last Modified 18-Dec-2000


	A Brief Guide to getting RAID set up with Linux

	First of all, download everything you need to build the kernel: The latest stable Linux Kernel (2.2 series) Notes: If you are not familiar with compiling your own kernels, configuring them, and patching, head to the end of this document, and download the one I've compiled. Download: `http://www.kernel.org/pub/linux/kernel/v2.2/linux-2.2.18.tar.bz2` The RAID patch Notes: The RAID currently shipping with the kernel is version 0.4, and was actively developed until 1996. After this, the RAID developers moved onto version 0.9. AFAIK, this patch is used by everybody using RAID under Linux as it is a whole lot faster, safer and stable. I have no idea why it is not included in the official kernel. Maintainer: `Ingo Molnar <mingo@redhat.com>` Download: `http://www.kernel.org/pub/linux/kernel/people/mingo/raid-patches/raid-2.2.18-A2` The RAID-1 read-balance patch Notes: This substantially improves RAID-1 read performance by "balancing" reads across all available partitions (like RAID-0 striping). It has been used by many people on the linux-raid list in mission-critical applications without problem. Maintainer: `Mika Kuoppala <mak@ikon.fi>` Download: `http://www.icon.fi/~mak/raid1/raid1readbalance-2.2.15-B2` The secure kernel patch Notes: The secure patch adds several security related enhancements to the kernel, its contents has historically (since 2.0) been rolled into the live kernel bit by bit. Again, used by many without problems. Maintainer: `Solar Designer <solar@openwall.com>` Download: `http://www.openwall.com/linux/linux-2.2.18-ow1.tar.gz` The VM-global patch Notes: The notorious `do_try_to_free_pages()` bug which has been plaguing the VM subsystem since 2.2.15 (see lkml) is still present in 2.2.18. This patch apparently fixes this. Rik van Riel has an alternative patch which also apparently fixes it. For some reason or other, neither patch is being incorporated into the 2.2 kernel series. I have heard from a number of RAID users that this works one for them - and it seems to be working for me. This patch should be considered alpha, but the alternatives (2.2.14/15 have a root exploit, 2.2.16-18 have a screwed VM subsystem) are not appealing. Maintainer: `Andrea Arcangeli <andrea@suse.de>` Download: `http://www.kernel.org/pub/linux/kernel/people/andrea/patches/v2.2/2.2.18/VM-global-2.2.18pre25-7.bz2` Meta-Patches Notes: These are my patches against the patches above to make them work for the latest kernel. If the versions I have listed above have been superseded, then use the later versions, otherwise use the previous version and fix it with the patch below. Download: `http://www.linuxraid.org/raid-2.2.18-A2-to-A3 http://www.linuxraid.org/raid1readbalance-2.2.15-B2-to-2.2.18-A0` `http://www.linuxraid.org/VM-global-2.2.18pre25-7-to-2.2.18-1` Uncompress these archives, and use my patches to patch the outdated patches (that was a bit of a mouthful, wasn't it?): tar xfI linux-2.2.18.tar.bz2 tar xfz linux-2.2.18-ow1.tar.gz bunzip2 VM-global-2.2.18pre25-7.bz2 patch VM-global-2.2.18pre25-7 VM-global-2.2.18pre25-7-to-2.2.18-1 mv VM-global-2.2.18pre25-7 VM-global-2.2.18-1 patch raid-2.2.18-A2 raid-2.2.18-A2-to-A3 mv raid-2.2.18-A2 raid-2.2.18-A3 patch raid1readbalance-2.2.15-B2 raid1readbalance-2.2.15-B2-to-2.2.18-A0 mv raid1readbalance-2.2.15-B2 raid1readbalance-2.2.18-A0 mv linux linux-2.2.18-cdhs cd linux-2.2.18-cdhs patch -p1 < ../raid-2.2.18-A3 patch -p1 < ../raid1readbalance-2.2.18-A0 patch -p1 < ../linux-2.2.18-ow1/linux-2.2.18-ow1.diff `patch -p1 < ../VM-global-2.2.18-1` You may also want to make a few other changes to the kernel - I've listed the ones I normally do below in case you find them helpful. Aim: Increase the number of processes that may run simultaneously Changes to `include/linux/tasks.h`: increase `NR_TASKS` from 512 to 3072 increase `MAX_TASKS_PER_USER` from `(NR_TASKS/2)` to 2048 increase `MIN_TASKS_LEFT_FOR_ROOT` from 4 to 32 Download: http://www.linuxraid.org/processes.patch Aim: Increase the number of files that may be open simultaneously Changes to `include/linux/fs.h`: increase `NR_FILE` from 4096 to 65536 increase `NR_RESERVED_FILES` from 10 to 128 Changes to `fs/inode.c`: increase `MAX_INODE` from 16384 to 262144 Note: `MAX_INODE` must be at least three times larger than `NR_FILE`. Download: http://www.linuxraid.org/filehandles.patch Aim: Decrease the time before disposing of unused TCP keepalive requests Changes to `include/net/tcp.h`: decrease `TCP_KEEPALIVE_TIME` from 2 hours to 5 minutes Download: http://www.linuxraid.org/tcp-keepalive.patch Aim: Increase the number of TCP/UDP ports that may be used simultaneously Changes to `net/ipv4/tcp_ipv4.c`: increase `sysctl_local_port_range` from 1024-4999 to 1024-9999 Download: http://www.linuxraid.org/tcp-port-range.patch Aim: Disable console screen blanking Changes to `drivers/char/console.c`: change `blank_screen()` to do nothing Note: If the kernel panics with the console blanked it is meant to unblank it so that you can see what happened pre-panic, and what the panic was. Either it doesn't, or the screen is blanked again, after the panic. This disables console blanking completely. Download: http://www.linuxraid.org/console-blanking.patch You may also want to use my kernel config as a starting point. It's aimed at a high-end server with i686, up to 2GB memory, SMP, IDE or SCSI disks, tapes and CD-ROMs, RAID, IP aliasing/firewalling, TCP syn cookies, serial console, 2048 UNIX PTYs, Enhanced RTC, Quota. So, to finish off: `make menuconfig make dep && make clean && make bzImage mv arch/i386/boot/bzImage /boot/vmlinux-2.2.18-cdhs vi /etc/lilo.conf lilo` `reboot` See also my heavily commented lilo.conf file. If you want to just try the kernel out straight off, and the config options sound close enough to you, you can download the compiled monolithic kernel or alternatively the modular kernel with network devices installed as modules. If you're lazy (like me) you might just want to download everything listed on this page as one big bad-ass patch against the 2.2.18 kernel.

Written by Corin Hartland-Swann for Commerce Internet Ltd