Re: RAID1 setup

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Official drives should be here Friday, so trying to get reading.

On 1/9/23 01:32, Simon Matter wrote:

Continuing this thread, and focusing on RAID1.

I got an HPE Proliant gen10+ that has hardware RAID support.  (can turn
it off if I want).
What exact model of RAID controller is this? If it's a S100i SR Gen10 then
it's not hardware RAID at all.

Yes, I found the information:
HPE Smart Array Gen10 Controllers Data Sheet.

Software RAID

· HPE Smart Array S100i SR Gen10 Software RAID


- HPE Smart Array S100i SR Gen10 SW RAID will operate in UEFI mode only. For legacy support an additional controller will be needed

- The S100i only supports Windows. For Linux users, HPE offers a solution that uses in-distro open-source software to create a two-disk RAID 1 boot volume. For more information visit:
I have yet to look at this url.

I am planning two groupings of RAID1 (it has 4 bays).

There is also an internal USB boot port.

So I am really a newbie in working with RAID.  From this thread it
sounds like I want /boot and /boot/efi on that USBVV boot device.
I suggest to use the USB device only to bot the installation medium, not
use it for anything used by the OS.

Will it work to put / on the first RAID group?  What happens if the 1st
drive fails and it is replaced with a new blank drive.  Will the config
in /boot figure this out or does the RAID hardware completely mask the 2
drives and the system runs on the good one while the new one is being

I am trying to grok what you are saying here.  is MD0-4 the physical disks or partitions?

All the drives I am getting are 4TB, as that is the smallest Enterprise quality HD I could find!  Quite overkill for me, $75 each.

I guess the best thing would be to use Linux Software RAID and create a
small RAID1 (MD0) device for /boot and another one for /boot/efi (MD1),

Here is sounds like MD0 and MD1 are partitions, not physical drives?

both in the beginning of disk 0 and 1 (MD2). The remaining space on disk 0
and 1 are created as another MD device. Disk 2 and 3 are also created as
one RAID1 (MD3) device. Formatting can be done like this

MD0 has filesystem for /boot
MD1 has filesystem for /boot/efi
MD2 is used as LVM PV
MD3 is used as LVM PV

Now it really seems like MDn are partitions with MD0-3 on disks 1&2 and MD3 on disks 3&4?

All other filesystems like / or /var or /home... will be created on LVM
Logical Volumes to give you full flexibility to manage storage.

Given using iRedMail which puts all mail store under /var/vmail, /var goes on disks 3&4.

/home will be little stuff.  iRedMail components put their configs and data (like domain and user sql database) all over the places. Disks 1&2 will be basically empty.  Wish I could have found high quality 1TB drives for less...



I also don't see how to build that boot USB stick.  I will have the
install ISO in the boot USB port and the 4 drives set up with hardware
RAID.  How are things figure out?  I am missing some important piece here.

Oh, HP does list Redhat support for this unit.

thanks for all help.


On 1/6/23 11:45, Chris Adams wrote:
Once upon a time, Simon Matter <simon.matter@xxxxxxxxx> said:
Are you sure that's still true? I've done it that way in the past but
seems at least with EL8 you can put /boot/efi on md raid1 with metadata
format 1.0. That way the EFI firmware will see it as two independent
filesystems. Only thing you have to be sure is that nothing ever writes
these filesystems when Linux is not running, otherwise your /boot/efi
raid will become corrupt.

Can someone who has this running confirm that it works?
Yes, that's even how RHEL/Fedora set it up currently I believe.  But
like you say, it only works as long as there's no other OS on the system
and the UEFI firmware itself is never used to change anything on the FS.
It's not entirely clear that most UEFI firmwares would handle a drive
failure correctly either (since it's outside the scope of UEFI), so IIRC
there's been some consideration in Fedora of dropping this support.

And... I'm not sure if GRUB2 handles RAID 1 /boot fully correctly, for
things where it writes to the FS (grubenv updates for "savedefault" for
example).  But, there's other issues with GRUB2's FS handling anyway, so
this case is probably far down the list.

I think that having RAID 1 for /boot and/or /boot/efi can be helpful
(and I've set it up, definitely not saying "don't do that"), but has to
be handled with care and possibly (probably?) would need manual
intervention to get booting again after a drive failure or replacement.

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