Root partition on raid?

Root partition on raid?

[Tonton]

This is mostly a shot in the dark, but is it feasible to have a /boot
partition with a initramfs on a partition of it's own and then all the rest
of / on a raid partition?

To make it work kernel, initramfs, mdadm, GRUB and some other tools would
need to be copied to the /boot partition from store, but this is potentially
worthwhile?


(My motivation is that I've a machine with raid "inside" and guix system on a
15G usb flash disk "outside". Lately it keeps running out of disk space when I
try out more interesting setups like http and similar)
-- 
    :)

Re: Root partition on raid?

[Tobias Geerinckx-Rice]

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Tonton,

Tonton wrote:
> This is mostly a shot in the dark, but is it feasible to have a 
> /boot
> partition with a initramfs on a partition of it's own and then 
> all the rest
> of / on a raid partition?

Sure.  I do this on my home server, so I never have to worry about 
rebooting headlessly after swapping a RAID drive (or have to 
install GRUB on every single one).

> To make it work kernel, initramfs, mdadm, GRUB and some other 
> tools would
> need to be copied to the /boot partition from store, but this is 
> potentially
> worthwhile?

You've lost me here, though.  Why is this needed?  What needs to 
work?

Oh…  are you using some hardware RAID that GRUB can't see?

Does it provide advantages that mdraid wouldn't?

Kind regards,

T G-R

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Re: Root partition on raid?

[Tonton]

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Hi, no, I use mdadm. Can GRUB see/use/boot this?

Maybe this is way easier than I thought. Could you share how you configure
this on your end? 

On Wed, 12 Jun 2019 17:52:09 +0200
Tobias Geerinckx-Rice <me@tobias.gr> wrote:

> Tonton,
> 
> Tonton wrote:
> > This is mostly a shot in the dark, but is it feasible to have a 
> > /boot
> > partition with a initramfs on a partition of it's own and then 
> > all the rest
> > of / on a raid partition?  
> 
> Sure.  I do this on my home server, so I never have to worry about 
> rebooting headlessly after swapping a RAID drive (or have to 
> install GRUB on every single one).
> 
> > To make it work kernel, initramfs, mdadm, GRUB and some other 
> > tools would
> > need to be copied to the /boot partition from store, but this is 
> > potentially
> > worthwhile?  
> 
> You've lost me here, though.  Why is this needed?  What needs to 
> work?
> 
> Oh…  are you using some hardware RAID that GRUB can't see?
> 
> Does it provide advantages that mdraid wouldn't?
> 
> Kind regards,
> 
> T G-R



-- 
    :)

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Re: Root partition on raid?

[Tobias Geerinckx-Rice]

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Tonton,

Tonton wrote:
> Hi, no, I use mdadm. Can GRUB see/use/boot this?

Yes!  Then I think Guix has everything you need.

> Maybe this is way easier than I thought. Could you share how you 
> configure
> this on your end? 

Nothing fancy:

--8<---------------cut here---------------start------------->8---
 (mapped-devices
  (list
   (mapped-device
    (type raid-device-mapping)
    (source (list "/dev/sda2" "/dev/sdb2" "/dev/sdc2" 
    "/dev/sde2"))
    (target "/dev/md0"))))
 (file-systems
  (cons*
   (file-system
    (dependencies mapped-devices) ; XXX is this needed?
    (device "/dev/md0")
    (mount-point "/")
    (type "btrfs")
    (options "compress=zlib,relatime"))
   (file-system
    (device (file-system-label "EFI"))
    (mount-point "/boot/efi") (create-mount-point? #t)
    (type "vfat"))
   %base-file-systems))

…

 (bootloader
  (bootloader-configuration
   (bootloader grub-efi-bootloader)
   (target "/boot/efi")
   (timeout (seconds 1))))
--8<---------------cut here---------------end--------------->8---

(That comment's been there for years; in true admin fashion I 
haven't touched a working set-up.)

Guix doesn't use mdadm.conf or whatever it's called.  Depending on 
your system, using labels or UUIDs instead of device names could 
make it more robust, or merely complicate drive replacement in 
future.

Adding LUKS to this mix should be possible too, but I haven't 
tried it myself.

Kind regards,

T G-R

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