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Help with RAID0 (dual raid)

Question

WildWayz    103

Hi guys

I have a remote dedicated server which has the following drives:
2 x 480GB SSD

2 x 6TB HDD

It is with the company Hetzner, so they have a Recovery System which allows you to remotely reload OS. I am using Ubuntu 18.04LTS - but same on 16.04.4 LTS.

Anyway, it is using software RAID, and installed the 2 x SSDs as RAID0 and I am wanting to have the 2 x HDDs also as RAID0, different array.

Here is what I am doing, with the SSDs already in RAID0:

 

View existing RAID arrays:  cat /proc/mdstat
 
Show your drives and mounts:    lsblk -o NAME,SIZE,FSTYPE,TYPE,MOUNTPOINT
NAME      SIZE FSTYPE            TYPE  MOUNTPOINT
sda     447.1G                   disk
├─sda1     32G linux_raid_member part
│ └─md0    64G swap              raid0 [SWAP]
├─sda2    512M linux_raid_member part
│ └─md1 511.4M ext3              raid1 /boot
└─sda3  414.6G linux_raid_member part
  └─md2   829G ext4              raid0 /
sdb     447.1G                   disk
├─sdb1     32G linux_raid_member part
│ └─md0    64G swap              raid0 [SWAP]
├─sdb2    512M linux_raid_member part
│ └─md1 511.4M ext3              raid1 /boot
└─sdb3  414.6G linux_raid_member part
  └─md2   829G ext4              raid0 /
sdc       5.5T                   disk
├─sdc1     32G linux_raid_member part
├─sdc2    512M linux_raid_member part
└─sdc3  414.6G linux_raid_member part
sdd       5.5T                   disk
├─sdd1     32G linux_raid_member part
├─sdd2    512M linux_raid_member part
└─sdd3  414.6G linux_raid_member part
 
if md3 exists already do: mdadm --stop /dev/md3
 
sdc and sdd will need their partitions killing first
 
Remove the RAID configuration from sdc and sdd
mdadm --zero-superblock /dev/sdc1
mdadm --zero-superblock /dev/sdc2
mdadm --zero-superblock /dev/sdc3
mdadm --zero-superblock /dev/sdd1
mdadm --zero-superblock /dev/sdd2
mdadm --zero-superblock /dev/sdd3
 
Will now show:
NAME      SIZE FSTYPE            TYPE  MOUNTPOINT
sda     447.1G                   disk
├─sda1     32G linux_raid_member part
│ └─md0    64G swap              raid0 [SWAP]
├─sda2    512M linux_raid_member part
│ └─md1 511.4M ext3              raid1 /boot
└─sda3  414.6G linux_raid_member part
  └─md2   829G ext4              raid0 /
sdb     447.1G                   disk
├─sdb1     32G linux_raid_member part
│ └─md0    64G swap              raid0 [SWAP]
├─sdb2    512M linux_raid_member part
│ └─md1 511.4M ext3              raid1 /boot
└─sdb3  414.6G linux_raid_member part
  └─md2   829G ext4              raid0 /
sdc       5.5T                   disk
├─sdc1     32G                   part
├─sdc2    512M                   part
└─sdc3  414.6G                   part
sdd       5.5T                   disk
├─sdd1     32G                   part
├─sdd2    512M                   part
└─sdd3  414.6G                   part
 
Remove the left over partitions:
fdisk /dev/sdc
press d
press 3
press d
press 2
press d
press w
 
Then the 2nd drive
fdisk /dev/sdd
press d
press 3
press d
press 2
press d
press w
 
Now reboot: reboot
 
Once it has rebooted, it will look like this:
moneysings@UniHosting-HELS:~$ lsblk -o NAME,SIZE,FSTYPE,TYPE,MOUNTPOINT
NAME      SIZE FSTYPE            TYPE  MOUNTPOINT
sda     447.1G                   disk
├─sda1     32G linux_raid_member part
│ └─md0    64G swap              raid0 [SWAP]
├─sda2    512M linux_raid_member part
│ └─md1 511.4M ext3              raid1 /boot
└─sda3  414.6G linux_raid_member part
  └─md2   829G ext4              raid0 /
sdb     447.1G                   disk
├─sdb1     32G linux_raid_member part
│ └─md0    64G swap              raid0 [SWAP]
├─sdb2    512M linux_raid_member part
│ └─md1 511.4M ext3              raid1 /boot
└─sdb3  414.6G linux_raid_member part
  └─md2   829G ext4              raid0 /
sdc       5.5T                   disk
sdd       5.5T                   disk
 
 
You will then need to use Parted - enter each one of these seperately:
You need to use following options inside parted:
parted /dev/sdc
mklabel gpt
unit TB
mkpart primary 0 -1
and then "q" for exit from the parted.
 
parted /dev/sdd
mklabel gpt
unit TB
mkpart primary 0 -1
and then "q" for exit from the parted.
 
 
Then just create md3 array:
 
mdadm --create /dev/md3 --verbose --level=0 --raid-devices=2 /dev/sdc1 /dev/sdd1
 
Now you will able to format md3:
 
mkfs.ext4 -m1 /dev/md3
 
It'll then show as RAID0 :D
 
root@UniHosting-HELS ~ # lsblk -o NAME,SIZE,FSTYPE,TYPE,MOUNTPOINT
NAME      SIZE FSTYPE            TYPE  MOUNTPOINT
sda     447.1G                   disk
├─sda1     32G linux_raid_member part
│ └─md0    64G swap              raid0 [SWAP]
├─sda2    512M linux_raid_member part
│ └─md1 511.4M ext3              raid1 /boot
└─sda3  414.6G linux_raid_member part
 └─md2   829G ext4              raid0 /
sdb     447.1G                   disk
├─sdb1     32G linux_raid_member part
│ └─md0    64G swap              raid0 [SWAP]
├─sdb2    512M linux_raid_member part
│ └─md1 511.4M ext3              raid1 /boot
└─sdb3  414.6G linux_raid_member part
 └─md2   829G ext4              raid0 /
sdc       5.5T                   disk
└─sdc1    4.6T linux_raid_member part
 └─md3   9.1T ext4              raid0
sdd       5.5T                   disk
└─sdd1    4.6T linux_raid_member part
 └─md3   9.1T ext4              raid0
 
 
Now, let's mount it as /home
mkdir -p /home
mount /dev/md3 /home
 
Let's see how it all looks:
 
moneysings@UniHosting-HELS:~$ df -h -x devtmpfs -x tmpfs
Filesystem      Size  Used Avail Use% Mounted on
/dev/md2        815G  3.9G  770G   1% /
/dev/md1        488M  207M  256M  45% /boot
/dev/md3         11T   61M   11T   1% /home
 
Sweeeeeeeeeeeeeet!
 
Save all the work we've done so it maintains it
 
mdadm --detail --scan | tee -a /etc/mdadm/mdadm.conf
update-initramfs -u
echo '/dev/md3 /home ext4 defaults,nofail,discard 0 0' | tee -a /etc/fstab
 
fstab should look like this:
 
pico /etc/fstab
proc /proc proc defaults 0 0
/dev/md/0 none swap sw 0 0
/dev/md/1 /boot ext3 defaults 0 0
/dev/md/2 / ext4 defaults 0 0
/dev/md3 /home ext4 defaults,nofail,discard 0 0
 
Reboot


When I reboot, the system won't come back up. I have to then go into Hetzners OS Installer and re-install the OS again... exactly as before.
When it comes up, the system boots up and both RAID arrays are working and all I need to do is mount the 2nd RAID array as /home
 

rm -Rf /home
mkdir -p /home
mount /dev/md3 /home
echo '/dev/md3 /home ext4 defaults,nofail,discard 0 0' | tee -a /etc/fstab
then rebooted


Now it works perfectly - but what am I doing wrong that I need to re-install the OS to actually get it to work?
I'm obviously missing a step.

Any help is appreciated

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5 answers to this question

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Mindovermaster    1,400

@BudMan, he can help here.

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WildWayz    103

Anyone? :D

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Ready2018    21

Software RAID 0 is never a good idea at the best of times. Not sure why you would want to do this anyway? I'm not sure that any internet connection is going to saturate the speed of the SSD, so having RAID 0 seems pointless and does not allow any redundancy considering it's a dedicated server.

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WildWayz    103
Just now, Ready2018 said:

Software RAID 0 is never a good idea at the best of times. Not sure why you would want to do this anyway? I'm not sure that any internet connection is going to saturate the speed of the SSD, so having RAID 0 seems pointless and does not allow any redundancy considering it's a dedicated server.

It's a 1Gbit link - purely for storage. Plus RAID0 is faster than Raid 1/5/6 etc
Sure, no redundancy - but I can usually re-set up the server in a few hours - probably faster than re-building a RAID array...

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Ready2018    21
44 minutes ago, WildWayz said:

It's a 1Gbit link - purely for storage. Plus RAID0 is faster than Raid 1/5/6 etc
Sure, no redundancy - but I can usually re-set up the server in a few hours - probably faster than re-building a RAID array...

As it's only 1Gbit link and purely for storage then it does not warrant RAID0 at all. It's more likely it give you issues (as you've already found out). You don't use RAID for it's quickness in re-building, but for the safety of your data.

 

Goodluck with your server.

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