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Re: Installer: problem installing onto LVM on RAID1




On 04/09/2017 08:43 PM, Ron Leach wrote:
> List, good evening,
> 
> I am trying to install Debian onto an LVM, and I want the LVM to use a
> pair of disks in a RAID1 configuration.  I'm having difficulty
> instructing the partitioner to do this.
> 
> I have a new, empty, machine with 2 x 3TB disks.  This new machine is
> intended to replace our existing users-files server, which has nearly
> exhausted its current fit of RAID1 on 2 x 2TB disks.  (The server of the
> files uses samba and NFS.)  Some time ago I received advice from the
> raid list that in future I could consider using an LVM so that when an
> existing volume is full it (if it is an LV) can be extended across
> additional disks.  Now that our existing system has reached its capacity
> limit, I'd like to replace it - and also take that advice.
> 
> While trying to install Debian 7.11/amd64 onto the new HW, I reach the
> partitioner and can (first) set up a single md (md0) RAID1 over the 2 x
> 3TB disks.  Next I can set up an LVM physical volume (3TB), and I can
> then set up a 3TB logical volume for '/'.  (I think I'm happy with the
> system, /home, and the general 'users-files' filesystem all sharing the
> one logical volume - similar to how a simple basic Debian install can be
> done on a whole disk.)
> 
> But the installer complains because I don't have any swap - and (in
> addition) I am unsure if I need to do something different for GRUB and
> booting.  I first tried using the 'guided' partitioner (I thought it
> might 'know best' about needing boot and / and so on) but I didn't seem
> to be able to ask it to use RAID *and* LVM.  I could ask it to make a
> RAID1, or an LVM.  May I ask the list a couple of questions?

Hi Ron.

> What partitions - I think I mean logical volumes - might I be best using
> for my installation, keeping in mind that I will need to extend whatever
> logical volume houses the 'users-files'?

Yes, it will be better LVM to be used in your case.
The hierarchy in LVM is:
 - physical volume - this can be a disk, RAID array or partition
 - volume group - this contains one or more physical volumes. In the
future you can add new physical volumes to volume group.
 - logical volume - this contains file system and files and belongs to
particular volume group.

> Is using a whole-disk RAID1 a reasonable choice (the kernel raid wiki
> suggests this will work) or would folks on the list recommend
> configuring multiple mds?

I don't know any downside of using one MD device.

If I was you I would do the following:
 - use GPT partition table for both disks
 - create one partition on each drive for Grub second stage image and
make it big enough. For EFI systems I read that the partition should be
about ~256MB, but if they are bigger that won't hurt, mine are 1GB.
 - create RAID partition on each disk and build one big RAID 1 array (a
MD device)
 - on top of this RAID 1 array create a physical volume
 - create a volume group and add the physical volume to it
 - create logical volumes for the system like you usually do. For
example some people create different file systems for:

/,
/home,
/usr,
/var, etc.

 - create a logical volume for your file server content
 - install the OS.

By the way I have not used LVM on Debian, but I believe that Linux LVM
HOWTO can be your friend.

HTH

Kind regards
Georgi