HowTo Single Disk to RAID - Cronologia

Svalo: Does the left TODO

2016-12-18T11:52:46Z

Does the left TODO

← Versione meno recente		Versione delle 11:52, 18 dic 2016
Riga 123:		Riga 123:
	update-grub		update-grub

	* TODO: tell about adding 'raid1' to the ~~kernel modules available in~~ initramfs ~~and how~~ to ~~rebuild it~~		We also had to update the initramfs to actually contain the raid module ans so we edited
			/etc/initramfs-tools/modules
			appending
			raid1
			to the list and executed
			update-initramfs
			to re-generate the initramfs

	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.

Chiromante il 16:49, 20 nov 2016

2016-11-20T16:49:00Z

← Versione meno recente		Versione delle 16:49, 20 nov 2016
Riga 3:		Riga 3:

	== 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 ~~tought~~ we didn't need a RAID for it. We installed ~~debian~~ stable 8.1, ~~sat~~ up every service, went to bed just to wake up with a hung server refusing to boot.		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 ~~expecially~~ because we do use commodity hardware taken from old computers.		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 ~~the~~ new disk of an equal size		* 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-~~memeber~~ disk		* 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 ~~partition befor the RAID~~		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 ~~createed~~ the filesystem for root		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 ~~choosed~~ ArchLinux as it's lightweight and provides all the packages we need without forcefully bringing up an installation procedure		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 ~~datas~~ over:		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 ~~wonderfull~~ piece of software that saves you from bind mounting /dev /proc and /sys in the chroot		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 ~~everithing~~ on the first try we edited the grub command line and the performed grub install from the booted system.		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

	~~Whiped~~ out all the old drive first 100M		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:

	* ~~Thougth~~ 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		* 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.

Svalo: /* Step by step guide */

2016-11-19T20:23:35Z

Step by step guide

← Versione meno recente		Versione delle 20:23, 19 nov 2016
Riga 50:		Riga 50:
	└─ba--system-swap 253:3 0 4G 0 lvm [SWAP]		└─ba--system-swap 253:3 0 4G 0 lvm [SWAP]

	The ~~fifth~~ partition is an extended one which contains the RAID one		The sdX2 partition is an extended one which contains the RAID one

	In this way we have two arrays, one for the boot and one for the LVM which contains the root and the swap		In this way we have two arrays, one for the boot and one for the LVM which contains the root and the swap

Svalo: Typos and fixes

2016-11-19T19:49:07Z

Typos and fixes

← Versione meno recente		Versione delle 19:49, 19 nov 2016
Riga 24:		Riga 24:

	First a layout of the partition befor the RAID		First a layout of the partition befor the RAID
	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
	├─sda2 8:2 0 1K 0 part		├─sda2 8:2 0 1K 0 part
	└─sda5 8:5 0 114.3G 0 part		└─sda5 8:5 0 114.3G 0 part
	~~├─ba~~--system-root 253:0 0 30G 0 lvm /		├─bitarno--system-root 253:0 0 30G 0 lvm /
	~~└─ba~~--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
Riga 49:		Riga 49:
	├─ba--system-root 253:0 0 30G 0 lvm /		├─ba--system-root 253:0 0 30G 0 lvm /
	└─ba--system-swap 253:3 0 4G 0 lvm [SWAP]		└─ba--system-swap 253:3 0 4G 0 lvm [SWAP]

			The fifth partition is an extended one which contains the RAID one

	In this way we have two arrays, one for the boot and one for the LVM which contains the root and the swap		In this way we have two arrays, one for the boot and one for the LVM which contains the root and the swap
Riga 71:		Riga 73:
	rsync -avPh /boot /mnt		rsync -avPh /boot /mnt
	sync && umount /mnt		sync && umount /mnt
	We were done with /boot, ~~ans~~ we needed to create the LVM volumes:		We were done with /boot, and we needed to create the LVM volumes:

	First we marked /dev/md2 as LVM member then we told LVM /dev/md2 was a device it could use		First we marked /dev/md2 as LVM member with fdisk then we told LVM /dev/md2 was a device it could use
	pvcreate /dev/md2		pvcreate /dev/md2

Riga 99:		Riga 101:
	mount /dev/md1 /mnt/new/boot		mount /dev/md1 /mnt/new/boot

	And arch-chroot'ed into it ~~arch~~-chroot is a wonderfull piece of software that saves you from bind mounting /dev /proc and /sys in the chroot		And arch-chroot'ed into it. Arch-chroot is a wonderfull piece of software that saves you from bind mounting /dev /proc and /sys in the chroot

	arch-chroot /mnt/new		arch-chroot /mnt/new
Riga 122:		Riga 124:
	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.

	This last step I simplified, we made several errors and had to boot into live several times, ~~because~~ we kept forgetting to add the needed modules and command lines arguments		This last step I simplified it, we made several errors and had to boot into live several times, as we kept forgetting to add the needed modules and command lines arguments

	To be sure to boot from the raid root you can edit the grub entry before booting, make sure it's like the following		To be sure to boot from the raid root you can edit the grub entry before booting, make sure it's like the following
Riga 147:		Riga 149:
	sfdisk /dev/sda < /tmp/savetablesde		sfdisk /dev/sda < /tmp/savetablesde

	~~And we~~ added the partitions to the array		We added the partitions to the array
	mdadm /dev/md1 --add /dev/sda1		mdadm /dev/md1 --add /dev/sda1
	mdadm /dev/md2 --add /dev/sda5		mdadm /dev/md2 --add /dev/sda5
Riga 153:		Riga 155:
	DONE!		DONE!

	~~You can check~~ the status of the resync of mdadm with		We then checked the status of the resync of mdadm with
	cat /proc/mdstat		cat /proc/mdstat

Svalo: Final edit, everything should be there

2016-11-19T19:41:45Z

Final edit, everything should be there

@@ Riga 3: / Riga 3: @@
 == Context ==
-We sat up a new/old server, [[BitArno]], it has a nice /home of ~6TB backed by a RAID and a separate dick for the / partition. As the drive for the / was tested before getting to production resulting in no errors we tought we didn't need a RAID for it. We installed debian stable 8.1, sat up every service, went to bet to wake up with a hung server refusing to boot.
+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 tought we didn't need a RAID for it. We installed debian stable 8.1, sat 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 expecially because we do use commodity hardware taken from old computers.
@@ Riga 22: / Riga 22: @@
 == Step by step guide ==
 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 partition befor the RAID
   sda                        8:0    0 114.5G  0 disk
@@ Riga 104: / Riga 105: @@
 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.
 == Issues ==

Svalo: Again, saving, not complete

2016-11-19T19:11:54Z

Again, saving, not complete

@@ Riga 14: / Riga 14: @@
 * Create a RAID1 array composed by 2 drives but with a drive marked as missing
 * 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)
-* Rsync the files on the new disk (member of the array)
+* 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-memeber disk
 * Check if everything is OK
@@ Riga 63: / Riga 63: @@
   mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sde1 missing
   mdadm --create /dev/md2 --level=1 --raid-devices=2 /dev/sde5 missing

Svalo: Partial content, just not to loose everything

2016-11-19T18:52:30Z

Partial content, just not to loose everything

Nuova pagina

We found ourselves in the need of switching from a single disk root to a root backed by a RAID, here's how we did.

== Context ==
We sat up a new/old server, [[BitArno]], it has a nice /home of ~6TB backed by a RAID and a separate dick for the / partition. As the drive for the / was tested before getting to production resulting in no errors we tought we didn't need a RAID for it. We installed debian stable 8.1, sat up every service, went to bet 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 expecially because we do use commodity hardware taken from old computers.

== 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:
* Poweroff the server and attach the new disk of an equal size
* Power on the server
* Create a RAID1 array composed by 2 drives but with a drive marked as missing
* 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)
* Rsync the files on the new disk (member of the array)
* Install the bootloader on the new drive adding the necessary modules for RAID and LVM
* Reboot the server from the RAID-memeber disk
* Check if everything is OK
* Add the old disk to the RAID and let mdadm resync the contents.

== Step by step guide ==
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 partition befor the RAID
sda 8:0 0 114.5G 0 disk
├─sda1 8:1 0 243M 0 part /boot
├─sda2 8:2 0 1K 0 part
└─sda5 8:5 0 114.3G 0 part
├─ba--system-root 253:0 0 30G 0 lvm /
└─ba--system-swap 253:3 0 4G 0 lvm [SWAP]

And after the switch

sda 8:0 0 114.5G 0 disk
├─sda1 8:1 0 243M 0 part
│ └─md1 9:1 0 242.8M 0 raid1 /boot
├─sda2 8:2 0 1K 0 part
└─sda5 8:5 0 114.3G 0 part
└─md2 9:2 0 114.2G 0 raid1
├─ba--system-root 253:0 0 30G 0 lvm /
└─ba--system-swap 253:3 0 4G 0 lvm [SWAP]
sde 8:64 0 114.5G 0 disk
├─sde1 8:65 0 243M 0 part
│ └─md1 9:1 0 242.8M 0 raid1 /boot
├─sde2 8:66 0 1K 0 part
└─sde5 8:69 0 114.3G 0 part
└─md2 9:2 0 114.2G 0 raid1
├─ba--system-root 253:0 0 30G 0 lvm /
└─ba--system-swap 253:3 0 4G 0 lvm [SWAP]

In this way we have two arrays, one for the boot and one for the LVM which contains the root and the swap

First of all we need to wipe out every possible header from the new disk as it will become a RAID member
dd if=/dev/zero of=/dev/sde bs=100M count=1

Then we created the partitions with sfdisk about the same size as the first disk. It's not needed for them to be the same as it wasn't possible to copy the partitions with dd

We need:
* one parition for the boot marked as Linux raid autodetect
* the other for LVM marked as Linux raid autodetect that takes the free space left

We then proceeded to create the 2 RAIDS, /dev/sde is the new disk
mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sde1 missing
mdadm --create /dev/md2 --level=1 --raid-devices=2 /dev/sde5 missing

== Issues ==

We (of course) had some issues in the process:

* Thougth 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 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.

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