Mirroring Disks
Solaris:
In Solaris 10, you can mirror the disks during the build process with Jumpstart, or even use ZFS mirroring. However, on older systems, you need to mirror the disks the old fashioned way with DiskSuite 4.2.1. In this example, the file names for the two disks being mirrored are c1t0d0sX and c1t1d0sX. The disks are partitioned like this:
/ c1t0d0s0 swap c1t0d0s1 /var c1t0d0s3 /usr c1t0d0s4 /opt c1t0d0s5 /export c1t0d0s6 - c1t0d0s7
Slice 7 is a 50mb partition used to store the metadatabaes! IMO, it is best practice to never use slice 7, except for this purpose!
1. You need to make sure the following packages are installed first:
SUNWmdr SUNWmdu SUNWmdx
This is the least you need to install! Oh and they will need to bzip to install successfully! They can be found on "Solaris 8 Software CD 2" (not sure for Solaris 9, but they could be part of the standard disto), in the following location:
cd $PATH_TO_CDROM/Solaris_8/EA/products/DiskSuite_4.2.1/sparc/Packages pkgadd -d . SUNWmdr SUNWmdu SUNWmdx
Once they are installed, reboot the box. It wouldn't hurt to do an 'init 0' and then a 'boot -r'!
2. Copy the primary disks VTOC to the secondary disk:
prtvtoc /dev/rdsk/c1t0d0s2 | fmthard -s - /dev/rdsk/c1t1d0s2
3. Create the metadatabases
metadb -f -a -c3 /dev/dsk/c1t0d0s7 metadb -f -a -c3 /dev/dsk/c1t1d0s7
4. Create and initialise the metadevices on the primary disk
metainit -f d10 1 1 c1t0d0s0 metainit -f d10 1 1 c1t0d0s1 metainit -f d10 1 1 c1t0d0s3 metainit -f d10 1 1 c1t0d0s4 metainit -f d10 1 1 c1t0d0s5 metainit -f d10 1 1 c1t0d0s6 metainit d0 -m d10 metainit d1 -m d11 metainit d3 -m d13 metainit d4 -m d14 metainit d5 -m d15 metainit d6 -m d16
5. Assign the root metadevice
metaroot d0
6. Edit /etc/vfstab and make sure that all the devices are changed to metadevices. So each line that looked like this
/dev/dsk/c1t0d0s3 /dev/rdsk/c1t0d0s3 /var ufs 1 no -
now looks like
/dev/md/dsk/d3 /dev/md/rdsk/d3 /var ufs 1 no -
7. Run the lockfs command and reboot
lockfs -fa reboot
8. Create the the metadevices on the secondary disk
metainit d20 1 1 c1t1d0s0 metainit d21 1 1 c1t1d0s1 metainit d23 1 1 c1t1d0s3 metainit d24 1 1 c1t1d0s4 metainit d25 1 1 c1t1d0s5 metainit d26 1 1 c1t1d0s6
9. Attach the metadevices from the secondary disk to the metadevices we booted from to start the mirroring process
metattach d0 d20 metattach d1 d21 metattach d3 d23 metattach d4 d24 metattach d5 d25 metattach d6 d26
You can monitor the progress of mirroring with this command:
metastat | grep -i progress
When it returns nothing, it's all finished.
10. Install the boot block on the secondary hard disk so that you can boot off it
installboot /usr/platform/`uname -i`/lib/fs/ufs/bootblk /dev/rdsk/c1t1d0s0
11. Disable the following in /etc/inetd.conf
100229/1 (rpc.metad) 100230/1 (rpc.metamhd)
12. Add this line to /etc/system so that the machine will boot if there are only 50% of the metadatabases available, i.e. a disk has failed
set md:mirrored_root_flag=1
You're now finished :)
CentOS/RedHat
DON'T USE THESE INSTRUCTIONS! I have yet to make them work properly!
OK, so software RAID on CentOS/RedHat sucks! Unless you build the box from the outset with mirrored disk, you're going to need to do a lot of work to get to a point where you're going to be happy. Wherever possible, mirror the disks during build! However, if the box is already built and you need to mirror the boot disk after the fact, here's how you do it:
This is a worked example that uses the following disk layout:
df -h Filesystem Size Used Avail Use% Mounted on /dev/sda6 3.9G 283M 3.4G 8% / /dev/sda7 40G 251M 37G 1% /var /dev/sda3 7.8G 764M 6.7G 11% /usr /dev/sda2 7.8G 147M 7.3G 2% /home /dev/sda1 99M 12M 82M 13% /boot tmpfs 1006M 0 1006M 0% /dev/shm
fdisk -l
Disk /dev/sda: 73.4 GB, 73407865856 bytes
255 heads, 63 sectors/track, 8924 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 13 104391 83 Linux
/dev/sda2 14 1057 8385930 83 Linux
/dev/sda3 1058 2101 8385930 83 Linux
/dev/sda4 2102 8924 54805747+ 5 Extended
/dev/sda5 2102 3145 8385898+ 82 Linux swap / Solaris
/dev/sda6 3146 3667 4192933+ 83 Linux
/dev/sda7 3668 8924 42226821 83 Linux
1. Make sure that 'mdadm' is installed:
yum install mdadm
2. Load the RAID kernel modules
modprobe linear modprobe multipath modprobe raid0 modprobe raid1 modprobe raid5 modprobe raid6 modprobe raid10
3. If the new disk 2 has previously been used in a server with RAID, you will need to stop and remove any meta devices that it had
mdadm --stop /dev/md0 mdadm --stop /dev/md1 mdadm --stop /dev/md2 mdadm --stop /dev/md3 mdadm --stop /dev/md4 mdadm --stop /dev/md5 mdadm --remove /dev/md0 mdadm --remove /dev/md1 mdadm --remove /dev/md2 mdadm --remove /dev/md3 mdadm --remove /dev/md4 mdadm --remove /dev/md5
4. Copy the partition table from one disk to the other
sfdisk -d /dev/sda | sfdisk /dev/sdb
5. Change the partition type of the second disk to 'raid':
fdisk /dev/sdb
The number of cylinders for this disk is set to 8924.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)
Command (m for help): t
Partition number (1-7): 1
Hex code (type L to list codes): fd
Command (m for help): t
Partition number (1-7): 2
Hex code (type L to list codes): fd
Etc. Repeat for all partitions and then exit:
Command (m for help): w
6. To make sure that there are no remains from previous RAID installations on /dev/sdb, we run the following commands:
mdadm --zero-superblock /dev/sdb1 mdadm --zero-superblock /dev/sdb2 mdadm --zero-superblock /dev/sdb3 mdadm --zero-superblock /dev/sdb5 mdadm --zero-superblock /dev/sdb6 mdadm --zero-superblock /dev/sdb7
7. Build the RAID devices using the 'mdadm' command:
mdadm -C /dev/md0 -n 2 -l 1 missing /dev/sdb1 mdadm -C /dev/md1 -n 2 -l 1 missing /dev/sdb2 mdadm -C /dev/md2 -n 2 -l 1 missing /dev/sdb3 mdadm -C /dev/md3 -n 2 -l 1 missing /dev/sdb5 mdadm -C /dev/md4 -n 2 -l 1 missing /dev/sdb6 mdadm -C /dev/md5 -n 2 -l 1 missing /dev/sdb7
Check your work:
cat /proc/mdstat
8. Create file a file system on each partition
mkfs.ext3 -j /dev/md0 mkfs.ext3 -j /dev/md1 mkfs.ext3 -j /dev/md2 mkfs.ext3 -j /dev/md4 mkfs.ext3 -j /dev/md5 mkswap /dev/md3
9. Update /etc/mdadm.conf
mdadm --detail --scan > /etc/mdadm.conf
10. Make a mount point and mount all the partitions:
mkdir /mnt/md mount /dev/md4 /mnt/md mkdir /mnt/md/boot mkdir /mnt/md/usr mkdir /mnt/md/var mkdir /mnt/md/home cd /mnt chmod -R 755 md/ mount /dev/md0 /mnt/md/boot mount /dev/md2 /mnt/md/usr mount /dev/md5 /mnt/md/var mount /dev/md1 /mnt/md/home
11. Copy the files from disk 1 to the newly built raid
rsync -aXv ––exclude=/proc/* ––exclude=/sys/* ––exclude=/dev/* ––exclude=/mnt/md / /mnt/md
NOTE: Remember to escape the * if you're using a shell like tcsh.
12. Edit /etc/fstab to use the appropriate metadevices.
LABEL=/ / ext3 defaults 1 1 LABEL=/var /var ext3 defaults 1 2 LABEL=/usr /usr ext3 defaults 1 2 LABEL=/home /home ext3 defaults 1 2 LABEL=/boot /boot ext3 defaults 1 2 tmpfs /dev/shm tmpfs defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0 LABEL=SWAP-sda5 swap swap defaults 0 0
becomes
/dev/md4 / ext3 defaults 1 1 /dev/md5 /var ext3 defaults 1 2 /dev/md2 /usr ext3 defaults 1 2 /dev/md1 /home ext3 defaults 1 2 /dev/md0 /boot ext3 defaults 1 2 tmpfs /dev/shm tmpfs defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0 /dev/md3 swap swap defaults 0 0
- 13. Edit /boot/grub/device.map and add the following entry for the second disk.
(hd1) /dev/sdb
13. Edit /boot/grub/menu.lst to allow fallback to the next kernel in the event of a boot failure:
vim /boot/grub/menu.lst
and add
default=0 fallback=1
14. Add an entry for in menu.lst to allow booting off metadevice root
title CentOS (2.6.18-194.26.1.el5 metadevices)
root (hd1,0)
kernel /vmlinuz-2.6.18-194.26.1.el5 ro root=/dev/md4
initrd /initrd-2.6.18-194.26.1.el5.img
title CentOS (2.6.18-194.26.1.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-194.26.1.el5 ro root=LABEL=/
initrd /initrd-2.6.18-194.26.1.el5.img
15. Rebuild ramdisk to reflect our new reality:
mv /boot/initrd-`uname -r`.img /boot/initrd-`uname -r`.img_orig mkinitrd /boot/initrd-`uname -r`.img `uname -r`
16. Setup GRUB on both disks
grub
Probing devices to guess BIOS drives. This may take a long time.
GNU GRUB version 0.97 (640K lower / 3072K upper memory)
[ Minimal BASH-like line editing is supported. For the first word, TAB
lists possible command completions. Anywhere else TAB lists the possible
completions of a device/filename.]
grub> root (hd0,0)
root (hd0,0)
Filesystem type is ext2fs, partition type 0x83
grub> setup (hd0)
setup (hd0)
Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... yes
Checking if "/grub/stage2" exists... yes
Checking if "/grub/e2fs_stage1_5" exists... yes
Running "embed /grub/e2fs_stage1_5 (hd0)"... 15 sectors are embedded.
succeeded
Running "install /grub/stage1 (hd0) (hd0)1+15 p (hd0,0)/grub/stage2 /grub/grub.conf"... succeeded
Done.
grub> root (hd1,0)
root (hd1,0)
Filesystem type is ext2fs, partition type 0xfd
grub> setup (hd1)
setup (hd1)
Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... yes
Checking if "/grub/stage2" exists... yes
Checking if "/grub/e2fs_stage1_5" exists... yes
Running "embed /grub/e2fs_stage1_5 (hd1)"... 15 sectors are embedded.
succeeded
Running "install /grub/stage1 (hd1) (hd1)1+15 p (hd1,0)/grub/stage2 /grub/grub.conf"... succeeded
Done.
grub> quit
17. Reboot and hope it works!
18. After the reboot, check that the metadevices have been used to boot from
df -h
should show:
19. Run fdisk on the original disk to change all the partitions to RAID volumes
fdisk /dev/sda
20. Add the disk 1 partitions to the meta devices
mdadm --add /dev/md0 /dev/sda1 mdadm --add /dev/md1 /dev/sda2 mdadm --add /dev/md2 /dev/sda3 mdadm --add /dev/md3 /dev/sda5 mdadm --add /dev/md4 /dev/sda6 mdadm --add /dev/md5 /dev/sda7
21. Monitor the re-sync with
cat /proc/mdstat
until all meta devices have, for want of a better word, synced.
22. Update /etc/mdadm.conf to reflect the new situation
mdadm --examine --scan > /etc/mdadm.conf
which should result in mdadm.conf looking something like:
23. Update grub so that in the event that disk 2 should fail, it will boot off disk 1
vim /boot/grub/menu.lst
so that it looks like this:
24. Now finally update the ramdisk one more time
mv /boot/initrd-`uname -r`.img /boot/initrd-`uname -r`.img_orig2 mkinitrd /boot/initrd-`uname -r`.img `uname -r`
25. Reboot and you should be good to go!
