What is the best way to set up RAID-1 on new Ubuntu install

What is the best way to set up RAID-1 on new Ubuntu install

[Jeffery Small]

I will be installing Xubuntu 24.04.3 on a newly built system having two
4TB Samsung M.2 SSDs which will be mirrored using RAID-1.  My question is
what is the better way to set up the mirror.  I'll have 128GB of RAM and
will be using a swapfile after installation.

Method #1: After the UEFI partition is created on both disks, create GPT
           /boot, / and /home partitions on each SSD and then create
	   three separate mirrors:

	   md0: /boot

	   md1: /

	   md2: /home

Method #2: After the UEFI partition is created on both disks, mirror md0
	   using the rest of the free space.  Then create GPT partitions
	   directly on the mirror:

	   md0p1: /boot

	   md0p2: /

	   md0p3: /home

This will be a straightforward desktop workstation, with no encryption or
support for multiple OS installs.  Are there advantages or possible pitfalls
with either approach?

I'm also considering eliminating the boot and home partitions and just
using a single root partition which feels strange after using UNIX for over
40 years. From a raid perspective does this also have advantages/pitfalls?

Thanks.
--
Jeffery Small

Re: What is the best way to set up RAID-1 on new Ubuntu install

[Wol]

On 03/09/2025 22:04, Jeffery Small wrote:
> I will be installing Xubuntu 24.04.3 on a newly built system having two
> 4TB Samsung M.2 SSDs which will be mirrored using RAID-1.  My question is
> what is the better way to set up the mirror.  I'll have 128GB of RAM and
> will be using a swapfile after installation.
> 
> Method #1: After the UEFI partition is created on both disks, create GPT
>             /boot, / and /home partitions on each SSD and then create
> 	   three separate mirrors:
> 
> 	   md0: /boot
> 
> 	   md1: /
> 
> 	   md2: /home
> 
> Method #2: After the UEFI partition is created on both disks, mirror md0
> 	   using the rest of the free space.  Then create GPT partitions
> 	   directly on the mirror:
> 
> 	   md0p1: /boot
> 
> 	   md0p2: /
> 
> 	   md0p3: /home
> 
> This will be a straightforward desktop workstation, with no encryption or
> support for multiple OS installs.  Are there advantages or possible pitfalls
> with either approach?
> 
> I'm also considering eliminating the boot and home partitions and just
> using a single root partition which feels strange after using UNIX for over
> 40 years. From a raid perspective does this also have advantages/pitfalls?
> 
DON'T mirror /boot. Unless you use 0.9 layout. It just makes setting up 
the boot more complicated. If anything goes wrong, 0.9 allows you to 
boot with no raid support.

128GB of ram? Why bother with a swapfile? Okay, I would create two 128GB 
swap partitions and set them equal priority, but that's me.

And what are you doing about /var? Does it really belong in the / partition?

With a 4TB setup, especially with a workstation, combining /, /var. and 
/home might be a sensible option. As I say, keep /boot out of it, but a 
single 3.5TB partition for everything else makes a lot of sense. How 
likely are you to run out of disk space? Highly unlikely? Then go for 
it! Remember most of the advice about Unix partitioning stems from the 
fact that K&R or T or whoever it was created the initial partitioning 
scheme simply because they were running out of space on a (by today's 
standards) tiny disk drive. Why stick with what they were forced to do?

Cheers,
Wol

Re: What is the best way to set up RAID-1 on new Ubuntu install

[Jeffery Small]

Wol <antlists@youngman.org.uk> writes:

>On 03/09/2025 22:04, Jeffery Small wrote:
>> I will be installing Xubuntu 24.04.3 on a newly built system having two
>> 4TB Samsung M.2 SSDs which will be mirrored using RAID-1.  My question is
>> what is the better way to set up the mirror.  I'll have 128GB of RAM and
>> will be using a swapfile after installation.
>> 
>> Method #1: After the UEFI partition is created on both disks, create GPT
>>             /boot, / and /home partitions on each SSD and then create
>> 	   three separate mirrors:
>> 
>> 	   md0: /boot
>> 
>> 	   md1: /
>> 
>> 	   md2: /home
>> 
>> Method #2: After the UEFI partition is created on both disks, mirror md0
>> 	   using the rest of the free space.  Then create GPT partitions
>> 	   directly on the mirror:
>> 
>> 	   md0p1: /boot
>> 
>> 	   md0p2: /
>> 
>> 	   md0p3: /home
>> 
>> This will be a straightforward desktop workstation, with no encryption or
>> support for multiple OS installs.  Are there advantages or possible pitfalls
>> with either approach?
>> 
>> I'm also considering eliminating the boot and home partitions and just
>> using a single root partition which feels strange after using UNIX for over
>> 40 years. From a raid perspective does this also have advantages/pitfalls?
>> 
>DON'T mirror /boot. Unless you use 0.9 layout. It just makes setting up 
>the boot more complicated. If anything goes wrong, 0.9 allows you to 
>boot with no raid support.

>128GB of ram? Why bother with a swapfile? Okay, I would create two 128GB 
>swap partitions and set them equal priority, but that's me.

>And what are you doing about /var? Does it really belong in the / partition?

>With a 4TB setup, especially with a workstation, combining /, /var. and 
>/home might be a sensible option. As I say, keep /boot out of it, but a 
>single 3.5TB partition for everything else makes a lot of sense. How 
>likely are you to run out of disk space? Highly unlikely? Then go for 
>it! Remember most of the advice about Unix partitioning stems from the 
>fact that K&R or T or whoever it was created the initial partitioning 
>scheme simply because they were running out of space on a (by today's 
>standards) tiny disk drive. Why stick with what they were forced to do?

>Cheers,
>Wol

Wol, thanks for the reply.  What is a 0.9 layout?  I've never heard of
that before.  I'm confused about why to not mirror the boot partition.
Other articles I've read on the subject suggest doing this.  What is the
problem?

Now maybe we are having a communication problem mixing up the initial
UEFI partition (mounted at /boot/efi) which does get set up on each SSD
independently and is definitely NOT mirrored, and the actual boot partition
(mounted as /boot) which is where GRUB and kernel are installed.  If I
made one big mirrored / partition, /boot could just be included along with
everything else.

As I say, I'm just trying to avoid future problem from something that I
didn't anticipate from the start.

Regards,
--
Jeff

Re: What is the best way to set up RAID-1 on new Ubuntu install

[Wol]

On 04/09/2025 05:54, Jeffery Small wrote:
> Wol, thanks for the reply.  What is a 0.9 layout?  I've never heard of
> that before. 

0.9 is an old layout. You'll notice that when raid details are posted it 
normally says "raid 1.2 format", which is the layout. All the raid 1.x 
formats have identical superblock format, the difference between the 
1.0, 1.1 and 1.2 formats is simply the location of the superblock. And 
it's always somewhere at the start of the partition.

0.9 is the old-style format. And it's placed at the end of the 
partition. So if the raid gets trashed somehow, because the filesystem 
starts at the start of the partition you can mount it directly if you 
have to.

> I'm confused about why to not mirror the boot partition.
> Other articles I've read on the subject suggest doing this.  What is the
> problem?
> 
I'm just thinking that if you do have boot trouble, this makes it easier 
to access your boot partition (which should be effectively read only 
almost all time), and might make recovering your system easier.

> Now maybe we are having a communication problem mixing up the initial
> UEFI partition (mounted at /boot/efi) which does get set up on each SSD
> independently and is definitely NOT mirrored, and the actual boot partition
> (mounted as /boot) which is where GRUB and kernel are installed.  If I
> made one big mirrored / partition, /boot could just be included along with
> everything else.
> 
Possibly. I've not got to grips with UEFI - I learnt most of my boot-fu 
back in the days of lilo :-)

> As I say, I'm just trying to avoid future problem from something that I
> didn't anticipate from the start.
> 
Cheers,
Wol

Re: What is the best way to set up RAID-1 on new Ubuntu install

[Reindl Harald]

Am 05.09.25 um 00:55 schrieb Wol:
>> Now maybe we are having a communication problem mixing up the initial
>> UEFI partition (mounted at /boot/efi) which does get set up on each SSD
>> independently and is definitely NOT mirrored, and the actual boot 
>> partition
>> (mounted as /boot) which is where GRUB and kernel are installed.  If I
>> made one big mirrored / partition, /boot could just be included along 
>> with
>> everything else.
>>
> Possibly. I've not got to grips with UEFI - I learnt most of my boot-fu 
> back in the days of lilo :-)
the UEFI partition must be FAT and can't be a RAID partition becaus eof 
the limitations of UEFI

Re: What is the best way to set up RAID-1 on new Ubuntu install

[Jeffery Small]

Reindl Harald <h.reindl@thelounge.net> writes:

>the UEFI partition must be FAT and can't be a RAID partition becaus eof 
>the limitations of UEFI

Good point.

Re: What is the best way to set up RAID-1 on new Ubuntu install

[Dragan Milivojević]

> the UEFI partition must be FAT and can't be a RAID partition becaus eof
> the limitations of UEFI

3rd attempt, let's see if this one gets through.
It can, at least on RHEL and derivatives.
From my notes: mdadm --verbose --create --assume-clean /dev/md/r1_efi
--name=r1_efi --level=1 --metadata=1.0 --raid-devices=7
/dev/nvme[0,2-3,5-8]n1p1
You have to select "EFI file system" for the file system in the
installation and that was it.

Re: What is the best way to set up RAID-1 on new Ubuntu install

[Pascal Hambourg]

On 05/09/2025 at 00:55, Wol wrote:
> 
> 0.9 is an old layout.

You could say "obsolete".

> the difference between the 
> 1.0, 1.1 and 1.2 formats is simply the location of the superblock. And 
> it's always somewhere at the start of the partition.

No, 1.0 superblock is at the end.

Re: What is the best way to set up RAID-1 on new Ubuntu install

[Adam Niescierowicz]

[-- Attachment #1.1: Type: text/plain, Size: 1544 bytes --]

W dniu 3.09.2025 o 23:04, Jeffery Small pisze:
> I will be installing Xubuntu 24.04.3 on a newly built system having two
> 4TB Samsung M.2 SSDs which will be mirrored using RAID-1.  My question is
> what is the better way to set up the mirror.  I'll have 128GB of RAM and
> will be using a swapfile after installation.
>
> Method #1: After the UEFI partition is created on both disks, create GPT
>             /boot, / and /home partitions on each SSD and then create
> 	   three separate mirrors:
>
> 	   md0: /boot
>
> 	   md1: /
>
> 	   md2: /home
>
> Method #2: After the UEFI partition is created on both disks, mirror md0
> 	   using the rest of the free space.  Then create GPT partitions
> 	   directly on the mirror:
>
> 	   md0p1: /boot
>
> 	   md0p2: /
>
> 	   md0p3: /home
>
> This will be a straightforward desktop workstation, with no encryption or
> support for multiple OS installs.  Are there advantages or possible pitfalls
> with either approach?
>
> I'm also considering eliminating the boot and home partitions and just
> using a single root partition which feels strange after using UNIX for over
> 40 years. From a raid perspective does this also have advantages/pitfalls?
>
> Thanks.
> --
> Jeffery Small

What about:

sda1 and sdb1 for EFI no raid sda2 and sdb2 RAID-10 with -f2 option 
(diffrent offset that gives double speed of read and single speed of write)

md0: LVM and on top of LVM you can create partitions with XFS 
filesystem. XFS allows you to realtime grow partitons.

-- 
---
Thanks
Adam Nieścierowicz

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Re: What is the best way to set up RAID-1 on new Ubuntu install

[Michael Reinelt]

Am Donnerstag, dem 04.09.2025 um 09:41 +0200 schrieb Adam Niescierowicz:
> What about:
> sda1 and sdb1 for EFI no raid sda2 and sdb2 RAID-10 with -f2 option (diffrent offset that gives
> double speed of read and single speed of write)
> md0: LVM and on top of LVM you can create partitions with XFS filesystem. XFS allows you to
> realtime grow partitons.

Depending on the user’s knowledge and experience, I’d vote for keeping simple setups simple:

Don’t use RAID-10 with far: it can make reshaping/growth complicated or impossible and mainly helps
long sequential reads. Just go for "classic" RAID-1.

Don’t add LVM unless there’s a clear benefit (multiple volumes, snapshots, thin provisioning).
Otherwise it’s just more moving parts.

Use Ext4 unless there’s a strong reason for XFS. Ext4 supports online grow; XFS cannot be shrunk.

regards, Michael

-- 
Michael Reinelt <michael@reinelt.co.at>
Ringsiedlung 75
A-8111 Gratwein-Straßengel
+43 676 3079941