[CentOS] RAID1 setup

Wed Jan 11 13:29:08 UTC 2023
Robert Moskowitz <rgm at htt-consult.com>

On 1/10/23 20:20, Robert Moskowitz wrote:
> 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
> Notes:
> - 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: 
> https://downloads.linux.hpe.com/SDR/project/lsrrb/
> ====================
> I have yet to look at this url.

This guide seems to answer MOST of my questions.

>>> 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?

I see from your response to another poster you ARE talking about RAID on 
individual partitions.  So I can better think about your approach now.


> 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...
> thanks
>> 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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