[CentOS] RAID1 setup

Wed Jan 11 01:20:54 UTC 2023
Robert Moskowitz <rgm at htt-consult.com>

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

On 1/9/23 01:32, Simon Matter wrote:
> Hi
>> 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
>> replicated?

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...


> Regards,
> Simon
>> 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.
>> Bob
>> On 1/6/23 11:45, Chris Adams wrote:
>>> Once upon a time, Simon Matter <simon.matter at invoca.ch> said:
>>>> Are you sure that's still true? I've done it that way in the past but
>>>> it
>>>> 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
>>>> FAT
>>>> filesystems. Only thing you have to be sure is that nothing ever writes
>>>> to
>>>> these filesystems when Linux is not running, otherwise your /boot/efi
>>>> md
>>>> 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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