Extend Raid 1 storage

winest · 28. Februar 2021

Hi, could someone give me clues about how to extend the storage?

Currently I have two 4TB drive in Raid 1. Recently the space is not enough, so I buy a new 8TB disk and hope to have a 8TB Raid 1 storage. That is

From

/mnt/sdb (4tb)

/mnt/sdc (4tb)

sdb and sdc forms a RAID 1, so available space is 4tb

To

/mnt/sdb (4tb)

/mnt/sdc (4tb)

new /mnt/sdd (8tb)

sdb and sdc forms a Raid 0, and then do Raid 1 with sdd, so totally 8tb available

But I have no experience to achieve it, so some questions need your help:

1. can this be done simply in web gui?

2. I guess the idea is to physically remove one of the 4TB disk, then insert new 8TB disk and do sync. Finallly install the removed 4TB disk back and convert those two 4TB disk to Raid 0. is this correct? If possible, please teach me more details. Thanks

curto · 3. März 2021

You can not do this through the GUI it is all CLI

I have never tried it - will spin up a VM now and check - but 99% this will not work as the RAID0 can not be added.

Will try it and advise back shortly

Craig

curto · 3. März 2021

Actually i was wrong - have just done it on a Centos 7 and it worked fine

But it is going to be messy for a beginner and can only really be done if you have somewhere else to copy the data as you set this up.

I personally would recommend maybe looking at UnionFS or MergeFS etc as a better solution - depending on what you plan on keeping on there

Craig

winest · 3. März 2021

Zitat von curto

Actually i was wrong - have just done it on a Centos 7 and it worked fine

But it is going to be messy for a beginner and can only really be done if you have somewhere else to copy the data as you set this up.

I personally would recommend maybe looking at UnionFS or MergeFS etc as a better solution - depending on what you plan on keeping on there

Craig

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Hi Craig,

Thanks for your reply. I have a bit question after reading the description.

1. Can't I simply copy the existing 4TB to my new 8TB disk and change the type of both 4TB disks?

2. I am not sure whether it's mandatory to format both 4TB disks if I want to convert them from Raid 1 to Raid 0. (Is there any metadata for Raid to work on those disk? or Raid information is stored on system disk and data disks simply contains data?)

I am working on Linux everyday so it's fine for me to use CLI but just has no experience about creating Raid.

If possible, could you share your steps? (commands without description is fine for me)

Thanks in advanced

curto · 7. März 2021

Ok yes you can do it.

1) Create a Standard partition and filesystem on the 8TB drive

2) Copy all of your data across from the 4TB drive onto the 8TB drive

3) Use Gdisk - delete the partitions on your 4TB Drives, create new partitions (slightly shorter than the total drive) make sure you mark them as fd00 (RAID type)

4) from the CLI create a RAID0 of the 2 x 4TB drive - wait until this has finished creating, then create a new RAID 1 set using the new /dev/md0 device - use the -missing command when you create it

5) Create filesystem, mount it etc and copy all your data across from the 8TB drive - now at this point you have no protection for your data if either 4TB drive fails

6) Use Gdisk again and delete the partition on the 8TB drive, create a new partition again mark it as fd00

7) from the CLI add this drive to the RAID1 set using mdadm

pray nothing goes wrong with the 4TB drives while you wait for this to sync

Craig

winest · 2. Mai 2021

Hi Craig,

Thanks a lot. I referenced your idea and finally extend it recently.

Here is full commands for others who might need to do in the future.

Assuming /dev/sdb and /dev/sdc are existing 4TB drive, and we are going to add /dev/sdd which is 8TB drive

Code

==================================================
Simulate current status in Windows
==================================================
1. open disk management to create vhdx
  $diskmgmt.msc
2. get DiskPath of vhdx by 
  $wmic diskdrive list brief
3. $wsl --mount <DiskPath> --bare


==================================================
Simulate current status in WSL2
==================================================
1. Check it's detected
  $lsblk -ap
2. Format with gdisk, mark them as fd00 (Linux Raid)
  $sudo gdisk /dev/sdb
  $sudo gdisk /dev/sdc
3. Create Raid 1
  $sudo mdadm --verbose --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1
4. Check mdadm progress
  $sudo mdadm --detail /dev/md0
  $cat /proc/mdstat
5. Format new md0
  $sudo mkfs -t ext4 /dev/md0
6. Mount
  $sudo mkdir -p /mnt/md0
  $sudo mount -t ext4 /dev/md0 /mnt/md0
7. Write some file to test


==================================================
Start real processing in WSL2, Stop FTP, SMB, all service except SSH in WebGui first
==================================================
1. Now, mount new drive, format with gdisk, mark it as 8300 (Linux Filesytem), so we can copy from /mnt/md0 to /dev/sdd
  $sudo gdisk /dev/sdd
  $sudo mkfs -t ext4 /dev/sdd1
2. Mount sdd
  $sudo mkdir -p /mnt/sdd1
  $sudo mount -t ext4 /dev/sdd1 /mnt/sdd1
3. Copy data from old md0 device to sdd
  $sudo rsync -avh --progress /mnt/md0/ /mnt/sdd1/

Choose either 4-1 or 4-2, I use 4-2 in the end
4-1. Convert md0 to Raid 0, will be slow because it will convert to Raid 4 first
  $sudo mdadm --grow --level=0 /dev/md0
  4-1-A. Check which disk is removed by previous step, add it back to md0
    $sudo mdadm --detail /dev/md0
    $sudo mdadm --grow --level=0 /dev/md0 --raid-devices=2 --add /dev/sdc1
4-2. Another faster way is to create a new md0
  $df -h, find all location using /dev/md0, and umount them
  $sudo mdadm --stop /dev/md0
  $sudo mdadm --verbose --create /dev/md0 --level=0 --raid-devices=2 /dev/sdb /dev/sdc

5. Create md1 which is Raid 1 with missing, because you have to create ext4 later
  $sudo umount /mnt/md0
  $sudo mdadm --verbose --create /dev/md1 --level=1 --raid-devices=2 /dev/md0 missing
  $sudo mkfs -t ext4 /dev/md1
6. Copy all files to md0
  $sudo mount -t ext4 /dev/md1 /mnt/md1
  $sudo rsync -avh --progress /mnt/sdd1/ /mnt/md1/
7. Unmount and format sdd, convert sdd to raid, add it back to md1
  $sudo umount /mnt/sdd1
  $sudo gdisk /dev/sdd
  $sudo mdadm --manage /dev/md1 --add /dev/sdd1
8. Update the path of fsname and mount directory in /etc/openmediavault/config.xml
  $sudo vim /etc/openmediavault/config.xml
  <mntent>
    <fsname>/dev/md1</fsname>
    <dir>/srv/MYRAID</dir>
9. Edit /etc/fstab to make sure it mount /mnt/md1, options are copied from existing entry created by openmediavault previously
  $sudo vim /etc/fstab
  /dev/md1 /srv/MYRAID ext4 defaults,nofail,user_xattr,noexec,usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv0,acl 0 2
10. Done. And if someday need to replace one disk, use /dev/md0 for example
  $sudo mdadm --manage /dev/md1 --fail /dev/md0
  $sudo mdadm --manage /dev/md1 --remove /dev/md0
  $sudo mdadm --manage /dev/md1 --add <new device>

Trouble shooting:
  $sudo mdadm --details
  $sudo cat /proc/mdstat
  $sudo fdisk -l
  $sudo mdadm --assemble --scan
  $sudo df -h



==================================================
Original thought which will failed because md0 has smaller size than md1
(possibly to fix by ensuring all device doesn't reserve any space at head and end)
==================================================
1. Now, mount new drive, format with gdisk, mark it as fd00 (Linux Raid)
  $sudo gdisk /dev/sdd
2. Create Raid 1 with missing parameter
  $sudo mdadm --verbose --create /dev/md1 --level=1 --raid-devices=2 /dev/sdd1 missing
  $sudo mkfs -t ext4 /dev/md1
  $sudo mkdir -p /mnt/md1
  $sudo mount -t ext4 /dev/md1 /mnt/md1
3. Copy data from old md0 device to new md1 device
  $sudo rsync -avh --progress /mnt/md0 /mnt/md1
4. Edit /etc/fstab to make sure it mount /mnt/md1
5. Convert md0 to Raid 0
  $sudo mdadm --grow --level=0 /dev/md0
6. Add the disk which was removed in previous step back to md0
  $sudo mdadm --grow /dev/md0 --raid-devices=2 --add /dev/sdb1
7. Logout and login again. Then add md0 to md1. Error happen because md0 has smaller size than md1 (because md0 is consist of 2 devices while md1 is only one device currently)

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Extend Raid 1 storage

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