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HowTo Single Disk to RAID: differenze tra le versioni
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== Context == | == Context == | ||
We sat up a new/old server, [[BitArno]], it has a nice /home of ~6TB backed by a RAID and a separate disk for the / partition. As the drive for the / was tested before getting to production resulting in no errors we | We sat up a new/old server, [[BitArno]], it has a nice /home of ~6TB backed by a RAID and a separate disk for the / partition. As the drive for the / was tested before getting to production resulting in no errors we thought we didn't need a RAID for it. We installed Debian stable 8.1, set up every service, went to bed just to wake up with a hung server refusing to boot. | ||
An on site check was required, we got there and found out that the / drive was failing to reallocate sectors, we fsck'ed it and it booted. "Great!" that same evening it was failing again and so we decided to switch from a single disk root to a RAID1 backed root | An on site check was required, we got there and found out that the / drive was failing to reallocate sectors, we fsck'ed it and it booted. "Great!" that same evening it was failing again and so we decided to switch from a single disk root to a RAID1 backed root especially because we do use commodity hardware taken from old computers. | ||
== The general idea == | == The general idea == | ||
We wanted a way to easily switch from a drive to the RAID without having to back everything up and copy it over again with fewer downtime possible and so we decided to: | We wanted a way to easily switch from a drive to the RAID without having to back everything up and copy it over again with fewer downtime possible and so we decided to: | ||
* Poweroff the server and attach | * Poweroff the server and attach a new disk of equal size | ||
* Power on the server | * Power on the server | ||
* Create a RAID1 array composed by 2 drives but with a drive marked as missing | * Create a RAID1 array composed by 2 drives but with a drive marked as missing (the new drive is the present one, the old one will be attached to the cluster later) | ||
* Set LVM up on top of it (as the old drive had LVM (it's a 120GB drive just for the `/` parition, we wanted to have some space available if we'll ever find in the need) | * Set LVM up on top of it (as the old drive had LVM (it's a 120GB drive just for the `/` parition, we wanted to have some space available if we'll ever find in the need) | ||
* Boot a live distro and copy / | * Boot a live distro and copy / | ||
** Install the bootloader on the new drive adding the necessary modules for RAID and LVM | ** Install the bootloader on the new drive adding the necessary modules for RAID and LVM | ||
* Reboot the server from the RAID- | * Reboot the server from the RAID-member disk | ||
* Check if everything is OK | * Check if everything is OK | ||
* Add the old disk to the RAID and let mdadm resync the contents. | * Add the old disk to the RAID and let mdadm resync the contents. | ||
| Riga 23: | Riga 23: | ||
Here I'll try to cover step by step the command we used, it has been a while since we did it so I'm not 100% sure I'll remember everything | Here I'll try to cover step by step the command we used, it has been a while since we did it so I'm not 100% sure I'll remember everything | ||
First a layout of the | First a layout of the partitions when it was single-disk | ||
sda 8:0 0 114.5G 0 disk | sda 8:0 0 114.5G 0 disk | ||
├─sda1 8:1 0 243M 0 part /boot | ├─sda1 8:1 0 243M 0 part /boot | ||
| Riga 31: | Riga 32: | ||
└─bitarno--system-swap 253:3 0 4G 0 lvm [SWAP] | └─bitarno--system-swap 253:3 0 4G 0 lvm [SWAP] | ||
And after the switch | And after the switch (newly created LVM has different volume group name but same size and structure) | ||
sda 8:0 0 114.5G 0 disk | sda 8:0 0 114.5G 0 disk | ||
| Riga 83: | Riga 84: | ||
lvcreate -L30G -n root ba-system | lvcreate -L30G -n root ba-system | ||
lvcreate -L4G -n swap ba-system | lvcreate -L4G -n swap ba-system | ||
We | We created the filesystem for root | ||
mkfs.ext4 /dev/mapper/ba--system-root | mkfs.ext4 /dev/mapper/ba--system-root | ||
And for swap | And for swap | ||
mkswap /dev/mapper/ba--system-swap | mkswap /dev/mapper/ba--system-swap | ||
Then it was time to poweroff the server and boot from a live, we | Then it was time to poweroff the server and boot from a live, we choose ArchLinux as it's lightweight and provides all the packages we need without forcefully bringing up an installation procedure | ||
We mounted the root partitions | We mounted the root partitions | ||
| Riga 95: | Riga 96: | ||
mount /dev/mapper/bitarno--system-root /mnt/old | mount /dev/mapper/bitarno--system-root /mnt/old | ||
And copied the | And copied the data over: | ||
rsync -avPh /mnt/old/ /mnt/new | rsync -avPh /mnt/old/ /mnt/new | ||
| Riga 101: | Riga 102: | ||
mount /dev/md1 /mnt/new/boot | mount /dev/md1 /mnt/new/boot | ||
And arch-chroot'ed into it. Arch-chroot is a | And arch-chroot'ed into it. Arch-chroot is a wonderful piece of software that saves you from bind mounting /dev /proc and /sys in the chroot | ||
arch-chroot /mnt/new | arch-chroot /mnt/new | ||
It was time to install grub and regenerate the image to contain LVM and RAID modules, this was the hardest part as we wrongly supposed all the modules were already present. | It was time to install grub on the new disk and regenerate grub configuration and the initram image to contain LVM and RAID modules, this was the hardest part as we wrongly supposed all the modules were already present. | ||
We added "domdadm" to GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub, the line should look something like | '''We added "domdadm"''' to GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub, the line should look something like | ||
cat /etc/default/grub| grep -i cmdli | cat /etc/default/grub| grep -i cmdli | ||
GRUB_CMDLINE_LINUX_DEFAULT="quiet domdadm" | GRUB_CMDLINE_LINUX_DEFAULT="quiet domdadm" | ||
And we added the modules needed to GRUB_PRELOAD_MODULES in the same file, if the line don't exist create it | And we '''added the modules needed to GRUB_PRELOAD_MODULES''' in the same file, if the line don't exist create it | ||
GRUB_PRELOAD_MODULES="lvm diskfilter mdraid1x" | GRUB_PRELOAD_MODULES="lvm diskfilter mdraid1x" | ||
| Riga 121: | Riga 122: | ||
And just to be sure | And just to be sure | ||
update-grub | update-grub | ||
* TODO: tell about adding 'raid1' to the kernel modules available in initramfs and how to rebuild it | |||
We exited from the chroot, unmounted everything, rebooted and kept our finger crossed till the password prompt of the root-on-RAID booted system. | We exited from the chroot, unmounted everything, rebooted and kept our finger crossed till the password prompt of the root-on-RAID booted system. | ||
| Riga 131: | Riga 134: | ||
linux /vmlinuz-3.16.0-4-amd64 root=/dev/mapper/ba--system-root ro quiet domdadm | linux /vmlinuz-3.16.0-4-amd64 root=/dev/mapper/ba--system-root ro quiet domdadm | ||
As we failed to achieve | As we failed to achieve everything on the first try we edited the grub command line and the performed grub install from the booted system. | ||
Once we managed to boot we had to finalize the process and add the old drive to the RAID array | Once we managed to boot we had to finalize the process and add the old drive to the RAID array | ||
| Riga 143: | Riga 146: | ||
vgchange -an bitarno--system | vgchange -an bitarno--system | ||
Wiped out all the old drive first 100M | |||
dd if=/dev/zero of=/dev/sda bs=100M count=1 | dd if=/dev/zero of=/dev/sda bs=100M count=1 | ||
sync | sync | ||
| Riga 162: | Riga 165: | ||
We (of course) had some issues in the process: | We (of course) had some issues in the process: | ||
* | * Thought the drive was of the same model the capacity was a little different and so we couldnt copy the partition scheme as we tougth we could do | ||
* It's very important to generate the grub image inserting the modules and the boot parameter needed for lvm and RAID | * It's very important to generate the grub image inserting the modules and the boot parameter needed for lvm and RAID | ||
* The initramfs must be rebuilt with the right raid module present in order for the kernel to find the cluster | |||
* It's impossible to backup and restore the lvm too as for a while we found ourselves with the 2 LVMs disk together and names were conflicting. | * It's impossible to backup and restore the lvm too as for a while we found ourselves with the 2 LVMs disk together and names were conflicting. | ||