[Nottingham] Growing a RAID 1

[J I]

Not wanting to add discs to the RAID, want to replace the current ones as
they are aged out.

Martin suggested on Signal using BTRFS to build out a new RAID 1 and then
switch, think I might go down that route.

On Wed, 18 Jan 2023 at 10:29, Brian Pickford via Nottingham <
nottingham at mailman.lug.org.uk> wrote:

> Hi,
>
> I'm far from an expert here, but I have setup and used arrays for as long
> as you have. Mine tend to fail more often though :(
>
> When replacing an array, I'd set up a new array with a temporary mount
> point say, /mnt/lib
> mkdir /mnt/lib
> set ownership as you need
> rsync the current array data to the temp so /var/lib to /mnt/lib
> use lsblk and blkid to get the UUID
> boot using a liveUSB
> alter my fstab to refer to the new UUID, keeping the old one either on a
> temp mount point or commented out
> check everything is OK, leave like this for a week or so, then remove the
> old drives
>
> Seems easier than trying to add disks of different sizes to your existing
> array
>
> Good luck
>
> On Tue, 17 Jan 2023 at 23:58, J I via Nottingham <
> nottingham at mailman.lug.org.uk> wrote:
>
>> Hello everyone, hope you are keeping well.
>>
>> I have an old RAID setup using drives from 2011 and whilst I've not had
>> issues, I am getting a bit nervous about them.
>>
>> At the moment both 2TB drives are in mdadm RAID1 (/dev/md0), and LVM sits
>> on top of that, the actual FS is the unexciting Ext4:
>> #lsblk
>> ...
>> sda                  8:0    0   1.8T  0 disk
>> └─md0                9:0    0   1.8T  0 raid1
>>  └─primary-varlib 253:0    0   1.8T  0 lvm   /var/lib
>> sdb                  8:16   0   1.8T  0 disk
>> └─md0                9:0    0   1.8T  0 raid1
>>  └─primary-varlib 253:0    0   1.8T  0 lvm   /var/lib
>> ...
>> As you  can see they are not boot, just data really.
>>
>> I want to replace them both with new 4TB Seagate IronWolfs
>>
>> Can anyone point me at some instructions on how to do that? My search-fu
>> is failing me and I have a feeling it's going to be more complicated than
>> just replacing the drives one at a time with a rebuild (and then some magic
>> to grow things to the full 4TB).
>>
>> Do I need to be overly concerned with /etc/fstab which seems to be using
>> a UUID:
>> /dev/disk/by-id/dm-uuid-LVM-47rf... /var/lib ext4 defaults 0 0
>>
>> This is all on Ubuntu Server 22.04.
>>
>> Cheers!
>>
>> J.
>>
>> Some more info if it helps:
>> #file -sL /dev/primary/varlib
>> /dev/primary/varlib: Linux rev 1.0 ext4 filesystem data...
>>
>> #mdadm --misc --detail /dev/md0
>> /dev/md0:
>>           Version : 1.2
>>     Creation Time : Sun May 24 15:00:15 2020
>>        Raid Level : raid1
>>        Array Size : 1953382464 (1862.89 GiB 2000.26 GB)
>>     Used Dev Size : 1953382464 (1862.89 GiB 2000.26 GB)
>>      Raid Devices : 2
>>     Total Devices : 2
>>       Persistence : Superblock is persistent
>>
>>     Intent Bitmap : Internal
>>
>>       Update Time : Tue Jan 17 23:22:16 2023
>>             State : clean
>>    Active Devices : 2
>>   Working Devices : 2
>>    Failed Devices : 0
>>     Spare Devices : 0
>>
>> Consistency Policy : bitmap
>>
>>              Name : ubuntu-server:0
>>              UUID : 7df346bb:a3c7ee5a:aa7ea17b:09c1c352
>>            Events : 88901
>>
>>    Number   Major   Minor   RaidDevice State
>>       0       8        0        0      active sync   /dev/sda
>>       1       8       16        1      active sync   /dev/sdb
>> --
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>> Nottingham at mailman.lug.org.uk
>> https://mailman.lug.org.uk/mailman/listinfo/nottingham
>>
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