[gentoo-user] best practise for 4 disks ... redundancy

[gentoo-user] best practise for 4 disks ... redundancy

[Stefan G. Weichinger]

greetings again

yesterday I received a shiny new server for a client.

It brings 4 x 1 TB SATA disks, is capable of UEFI and I started setting
it up.

GPT partitioning, small partition(s) for the ESP, some swap, and bigger
partitions of type fd=raid for creating 2 mdadm-raids (rootfs and data)
with level 6.

ok so far.

Then I spent some hours fiddling with grub2, gummiboot et al to get that
box booting up fine. dracut doesn't assemble the rootfs-raid etc etc ...
-> fun

What the question is in general:

even if I manage to have it booting via UEFI from /dev/sda1 or so ... I
still have this single point of failure as the vfat-partitioned ESP is
on one physical disk only.

I would like to set it up in a way that it boots even when the /dev/sda
dies ...

Maybe I have to go the BIOS way and have an ext2-boot-raid1 over 4
disks/partitions? I did that on other servers back then.

What is the up-to-date and recommended way of achieving this?
How do you gentoo-users do these things?

I am still at the start with this server and don't mind backing up the
rootfs and start from scratch with partitioning ;)

Thanks, Stefan

Re: [gentoo-user] best practise for 4 disks ... redundancy

[Neil Bothwick]

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On Wed, 11 Mar 2015 07:45:54 +0100, Stefan G. Weichinger wrote:

> yesterday I received a shiny new server for a client.
> 
> It brings 4 x 1 TB SATA disks, is capable of UEFI and I started setting
> it up.
> 
> GPT partitioning, small partition(s) for the ESP, some swap, and bigger
> partitions of type fd=raid for creating 2 mdadm-raids (rootfs and data)
> with level 6.
> 
> ok so far.
> 
> Then I spent some hours fiddling with grub2, gummiboot et al to get that
> box booting up fine. dracut doesn't assemble the rootfs-raid etc etc ...
> -> fun

I found this with a LUKS root filesystem, dracut doesn't automatically
detect such devices any more, so speed up the boot. You need to specify
rd.auto or rd.mdraid to force it.

> even if I manage to have it booting via UEFI from /dev/sda1 or so ... I
> still have this single point of failure as the vfat-partitioned ESP is
> on one physical disk only.
> 
> I would like to set it up in a way that it boots even when the /dev/sda
> dies ...

I generally set up boot on a RAID1 across all disks. You can still
access individual disks in a RAID1 array, so you can set your computer
to boot from sda1 then sda2 etc but mount /boot on the array, so all
updates are pushed to all four disks.
 

-- 
Neil Bothwick

I distinctly remember forgetting that.

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Re: [gentoo-user] best practise for 4 disks ... redundancy

[Stefan G. Weichinger]

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On 11.03.2015 12:09, Neil Bothwick wrote:

>> Then I spent some hours fiddling with grub2, gummiboot et al to
>> get that box booting up fine. dracut doesn't assemble the
>> rootfs-raid etc etc ... -> fun
> 
> I found this with a LUKS root filesystem, dracut doesn't
> automatically detect such devices any more, so speed up the boot.
> You need to specify rd.auto or rd.mdraid to force it.

I think, both ... I will have a look next time.

> I generally set up boot on a RAID1 across all disks. You can still 
> access individual disks in a RAID1 array, so you can set your
> computer to boot from sda1 then sda2 etc but mount /boot on the
> array, so all updates are pushed to all four disks.

So RAID1 with vfat as ESP ?

S

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Re: [gentoo-user] best practise for 4 disks ... redundancy

[Neil Bothwick]

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On Wed, 11 Mar 2015 16:52:27 +0100, Stefan G. Weichinger wrote:

> > I generally set up boot on a RAID1 across all disks. You can still 
> > access individual disks in a RAID1 array, so you can set your
> > computer to boot from sda1 then sda2 etc but mount /boot on the
> > array, so all updates are pushed to all four disks.  

That should have read "sda1 then sdb1".
 
> So RAID1 with vfat as ESP ?

That's how I'd do it. I have /boot on RAID1 on this box (but not as FAT
and it's a BIOS motherboard) with everything else on a btrfs RAID and it
works well.


-- 
Neil Bothwick

A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

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Re: [gentoo-user] best practise for 4 disks ... redundancy

[Stefan G. Weichinger]

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Am 11.03.2015 um 17:06 schrieb Neil Bothwick:

>> So RAID1 with vfat as ESP ?
> 
> That's how I'd do it. I have /boot on RAID1 on this box (but not as
> FAT and it's a BIOS motherboard) with everything else on a btrfs
> RAID and it works well.

I will redo my setup tomorrow ... thanks
So your suggestion is with MBR and not GPT?

I still wonder if to do UEFI and GPT because both are the more modern
ways of doing things (and be prepared for future developments) or just
stay with BIOS and MBR as long as I don't need it (with disks smaller
than 2 TB etc)

S
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Re: [gentoo-user] best practise for 4 disks ... redundancy

[Neil Bothwick]

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On Wed, 11 Mar 2015 23:14:49 +0100, Stefan G. Weichinger wrote:

> Am 11.03.2015 um 17:06 schrieb Neil Bothwick:
> 
> >> So RAID1 with vfat as ESP ?  
> > 
> > That's how I'd do it. I have /boot on RAID1 on this box (but not as
> > FAT and it's a BIOS motherboard) with everything else on a btrfs
> > RAID and it works well.  
> 
> I will redo my setup tomorrow ... thanks
> So your suggestion is with MBR and not GPT?

Absolutely not! MBR is fragile, limited and horrible. I use GPT but not
UEFI because this is a pre-UEFI motherboard.

> I still wonder if to do UEFI and GPT because both are the more modern
> ways of doing things (and be prepared for future developments) or just
> stay with BIOS and MBR as long as I don't need it (with disks smaller
> than 2 TB etc)

Given the choice, I'd use GPT for the above reasons and UEFI because
Gummiboot is nicer than GRUB.


-- 
Neil Bothwick

During a raid on a local chemist's shop, 2000 Viagra tablets were stolen
Police are looking for hardened criminals!

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Re: [gentoo-user] best practise for 4 disks ... redundancy

[Stefan G. Weichinger]

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On 11.03.2015 23:32, Neil Bothwick wrote:
> On Wed, 11 Mar 2015 23:14:49 +0100, Stefan G. Weichinger wrote:
> 
>> Am 11.03.2015 um 17:06 schrieb Neil Bothwick:
>> 
>>>> So RAID1 with vfat as ESP ?
>>> 
>>> That's how I'd do it. I have /boot on RAID1 on this box (but
>>> not as FAT and it's a BIOS motherboard) with everything else on
>>> a btrfs RAID and it works well.
>> 
>> I will redo my setup tomorrow ... thanks So your suggestion is
>> with MBR and not GPT?
> 
> Absolutely not! MBR is fragile, limited and horrible. I use GPT but
> not UEFI because this is a pre-UEFI motherboard.
> 
>> I still wonder if to do UEFI and GPT because both are the more
>> modern ways of doing things (and be prepared for future
>> developments) or just stay with BIOS and MBR as long as I don't
>> need it (with disks smaller than 2 TB etc)
> 
> Given the choice, I'd use GPT for the above reasons and UEFI
> because Gummiboot is nicer than GRUB.

I now have a dedicated ESP on /dev/sda2 (non-RAID) and it boots via
gummiboot (-> UEFI).

dracut assembles the arrays after configuring this:

# /etc/dracut.conf

add_dracutmodules+="lvm bash mdraid"

hostonly="yes"

mdadmconf="yes"

# the uuids of my two arrays ...
kernel_cmdline+=" rd.md.uuid=7663e24a:1a64ce0f:49545629:46742031 "
kernel_cmdline+=" rd.md.uuid=8c266e7a:870c97b7:ff199683:6d8c3edb "

# end


(lvm isn't necessary but doesn't hurt)

I now wonder if I could

(a) create a RAID1 over /dev/sd[abcd]2 and format it as vfat ESP

or

(b) "clone" /dev/sda2 -> format each /dev/sd[abcd]2 as vfat, copy the
content of /boot in there and install gummiboot to each harddisk

?

Stefan

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Re: [gentoo-user] best practise for 4 disks ... redundancy

[Neil Bothwick]

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On Thu, 12 Mar 2015 12:30:45 +0100, Stefan G. Weichinger wrote:

> I now have a dedicated ESP on /dev/sda2 (non-RAID) and it boots via
> gummiboot (-> UEFI).
> 
> I now wonder if I could
> 
> (a) create a RAID1 over /dev/sd[abcd]2 and format it as vfat ESP
> 
> or
> 
> (b) "clone" /dev/sda2 -> format each /dev/sd[abcd]2 as vfat, copy the
> content of /boot in there and install gummiboot to each harddisk
> 
c) Create a 4 disk RAID1 array consisting of sda2 and 3 missing disks.
Then add sdb2, sdc2, sdd2 in turn and the contents of sda2 will be
replicated to them.


-- 
Neil Bothwick

Make it idiot proof and someone will make a better idiot.

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Re: [gentoo-user] best practise for 4 disks ... redundancy

[Stefan G. Weichinger]

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On 12.03.2015 17:48, Neil Bothwick wrote:

> c) Create a 4 disk RAID1 array consisting of sda2 and 3 missing
> disks. Then add sdb2, sdc2, sdd2 in turn and the contents of sda2
> will be replicated to them.

the array formatted as vfat (-> ESP) ?

will try, thanks

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Re: [gentoo-user] best practise for 4 disks ... redundancy

[Neil Bothwick]

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On Thu, 12 Mar 2015 18:12:06 +0100, Stefan G. Weichinger wrote:

> > c) Create a 4 disk RAID1 array consisting of sda2 and 3 missing
> > disks. Then add sdb2, sdc2, sdd2 in turn and the contents of sda2
> > will be replicated to them.  
> 
> the array formatted as vfat (-> ESP) ?

sda2 is already formatted as FAT with the correct contents. 


-- 
Neil Bothwick

Tribble math: * + * = ***********************************

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Re: [gentoo-user] best practise for 4 disks ... redundancy

[Stefan G. Weichinger]

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On 12.03.2015 18:28, Neil Bothwick wrote:
> On Thu, 12 Mar 2015 18:12:06 +0100, Stefan G. Weichinger wrote:
> 
>>> c) Create a 4 disk RAID1 array consisting of sda2 and 3
>>> missing disks. Then add sdb2, sdc2, sdd2 in turn and the
>>> contents of sda2 will be replicated to them.
>> 
>> the array formatted as vfat (-> ESP) ?
> 
> sda2 is already formatted as FAT with the correct contents.

partition type ?

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Re: [gentoo-user] best practise for 4 disks ... redundancy

[Stefan G. Weichinger]

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On 12.03.2015 19:52, Stefan G. Weichinger wrote:
> On 12.03.2015 18:28, Neil Bothwick wrote:
>> On Thu, 12 Mar 2015 18:12:06 +0100, Stefan G. Weichinger wrote:
> 
>>>> c) Create a 4 disk RAID1 array consisting of sda2 and 3 
>>>> missing disks. Then add sdb2, sdc2, sdd2 in turn and the 
>>>> contents of sda2 will be replicated to them.
>>> 
>>> the array formatted as vfat (-> ESP) ?
> 
>> sda2 is already formatted as FAT with the correct contents.

yes ... and after that?

install gummiboot to each physical disk?
create new loader-entries ?

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Re: [gentoo-user] best practise for 4 disks ... redundancy

[Neil Bothwick]

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On Fri, 13 Mar 2015 09:38:15 +0100, Stefan G. Weichinger wrote:

> >>>> c) Create a 4 disk RAID1 array consisting of sda2 and 3 
> >>>> missing disks. Then add sdb2, sdc2, sdd2 in turn and the 
> >>>> contents of sda2 will be replicated to them.  
       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

> >>> 
> >>> the array formatted as vfat (-> ESP) ?  
> >   
> >> sda2 is already formatted as FAT with the correct contents.  
> 
> yes ... and after that?
> 
> install gummiboot to each physical disk?
> create new loader-entries ?

See above. The reason for using a RAID1 array is to avoid having to
update multiple disks, just mount /boot on the RAID device.

% mount | grep boot
/dev/md0 on /boot type ext2 (rw,noatime,stripe=4)


-- 
Neil Bothwick

Ifyoucanreadthis,youspendtoomuchtimefiguringouttaglines.

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Re: [gentoo-user] best practise for 4 disks ... redundancy

[Stefan G. Weichinger]

Am 2015-03-13 um 09:59 schrieb Neil Bothwick:

> See above. The reason for using a RAID1 array is to avoid having
> to update multiple disks, just mount /boot on the RAID device.
> 
> % mount | grep boot /dev/md0 on /boot type ext2
> (rw,noatime,stripe=4)

/boot is my vfat ESP here .. no ext2 ...

Re: [gentoo-user] best practise for 4 disks ... redundancy

[Neil Bothwick]

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On Fri, 13 Mar 2015 14:55:27 +0100, Stefan G. Weichinger wrote:

> > See above. The reason for using a RAID1 array is to avoid having
> > to update multiple disks, just mount /boot on the RAID device.
> > 
> > % mount | grep boot /dev/md0 on /boot type ext2
> > (rw,noatime,stripe=4)  
> 
> /boot is my vfat ESP here .. no ext2 ...

That makes no difference, the filesystem sits on top of the RAID.

As I said, that computer is pre-UEFI, so /boot is ext2. But RAID doesn't
care about the filesystem, it just mirrors the bits.


-- 
Neil Bothwick

Pedestrians come in two types: Quick or Dead.

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Re: [gentoo-user] best practise for 4 disks ... redundancy

[Stefan G. Weichinger]

Am 2015-03-13 um 15:11 schrieb Neil Bothwick:
> On Fri, 13 Mar 2015 14:55:27 +0100, Stefan G. Weichinger wrote:
> 
>>> See above. The reason for using a RAID1 array is to avoid
>>> having to update multiple disks, just mount /boot on the RAID
>>> device.
>>> 
>>> % mount | grep boot /dev/md0 on /boot type ext2 
>>> (rw,noatime,stripe=4)
>> 
>> /boot is my vfat ESP here .. no ext2 ...
> 
> That makes no difference, the filesystem sits on top of the RAID.
> 
> As I said, that computer is pre-UEFI, so /boot is ext2. But RAID
> doesn't care about the filesystem, it just mirrors the bits.

Tried your suggestion today .. worked out great after adding that new
array to dracut.conf ;)

Thanks!

goes into my howtos ...