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Re: How to Boot with LVM

From ray <ray@aarden.us>
Newsgroups linux.debian.user
Subject Re: How to Boot with LVM
Date 2015-09-08 02:00 +0200
Message-ID <q6eum-42W-5@gated-at.bofh.it> (permalink)
References <q5ybL-2wJ-7@gated-at.bofh.it> <q62CS-3We-23@gated-at.bofh.it> <q6eum-42W-7@gated-at.bofh.it>
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Rick,

Thank you for responding and providing all the info.  

On Monday, September 7, 2015 at 6:20:07 AM UTC-5, Rick Thomas wrote:
> On Sep 5, 2015, at 7:24 PM, ray wrote:
> 
> > I would like to configure LVMs for everything including boot.
> 
> Is it "just for fun" or do you have a real-world reason for wanting everything, including boot, to be on LVM?
Lack of knowledge.  I was expecting it to be cleaner.  But it no longer looks that way.
> 
> I'll describe my own typical setup (special purpose systems may have different setups to meet special purpose needs).  For purposes of illustration, I'll describe a system with two identical disks.  The principles should be clear as they apply to systems with larger or more varied configurations.  If you have only a single disk, you can skip the RAID parts in this and go straight to LVM.

I have 3 pairs of SSDs, each pair in a RAID0. 
> 
> I configure a small (<1GB) "/boot" partition as a primary partition (e.g. /dev/sda1) on one of the disks, with the same space on the other disk unused. [1]  I make another primary partition (e.g. /dev/sd[ab]2) , on each of the disks, sized to be one half of the size I want for my swap.  The rest of the space on each disk goes into a single, large, logical partition (e.g. /dev/sd[ab]5).
> 
This is similar to my setup.  I have the swaps on a separate RAID0.

> The two swap partitions I set up as a RAID0 (e.g. /dev/md0).  This will be my system swap. [2]
> 
> The two large logical partitions, I configure into a RAID1 (e.g. /dev/md1). [3]
> 
I made my large partition a primary.  Could this be problematic?

> I configure the RAID1 as the physical volume for a single volume group which I partition using LVM into a root that's big enough to be about 50% full when fully installed,  and /home that's as big as I think I'll need for my users.  The remainder of the VG I leave unconfigured, so I can grow into it as needs become apparent over time.
> 
> If I have enough RAM to make it useful, I'll put /tmp on a tmpfs.  I size it at about 50% of my swap space.  With a smaller RAM, I make a separate logical volume for /tmp.
> 
I would like to know more about the purpose of these criteria - please.

> [1] I know there are ways to make grub work with RAID1, but it's too complicated for me to get it right.  Instead, I just make regular backups of the /boot partition.  If the disk with /boot on it develops a bad spot in an inconvenient place, I simply boot from a CD in rescue mode and restore the contents of /boot from a backup into the unused space that I reserved on the other disk.

Yes, that was my plan also.  But it was also my plan to backup the rest of the system to HDD.  As such, I planned for no redundancy in drive configuration and only stripe for speed.

> 
> [2] There's no particular point in putting swap on a redundant RAID.  If your swap develops a bad spot, you probably want to boot from a CD into rescue mode ASAP so you can take necessary measures to fix the problem.  Using RAID1 for swap would just mask the problem -- possibly until it's too late.
> 
> [3] Conversely, everything else on the system wants to be redundantly protected.  If I have three or more disks, I'll use RAID5; with four or more I might opt for RAID6.
> 
> Here's an example:
> 
> rbthomas@monk:~$ lsblk
> NAME             MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
> sda                8:0    0 465.8G  0 disk  
> |-sda1             8:1    0   953M  0 part  /boot
> |-sda2             8:2    0  18.6G  0 part  
> | `-md0            9:0    0  37.3G  0 raid0 [SWAP]
> |-sda3             8:3    0     1K  0 part  
> `-sda5             8:5    0 446.2G  0 part  
>   `-md1            9:1    0 446.1G  0 raid1 
>     |-root-root  253:0    0  18.6G  0 lvm   /
>     `-root-home  253:3    0   210G  0 lvm   /home
> sdb                8:16   0 465.8G  0 disk  
> |-sdb1             8:17   0   953M  0 part  
> |-sdb2             8:18   0  18.6G  0 part  
> | `-md0            9:0    0  37.3G  0 raid0 [SWAP]
> |-sdb3             8:19   0     1K  0 part  
> `-sdb5             8:21   0 446.2G  0 part  
>   `-md1            9:1    0 446.1G  0 raid1 
>     |-root-root  253:0    0  18.6G  0 lvm   /
>     `-root-home  253:3    0   210G  0 lvm   /home
> sr0               11:0    1  1024M  0 rom   
> 
> 
> Enjoy!
> Rick

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Thread

How to Boot with LVM ray <ray@aarden.us> - 2015-09-06 04:50 +0200
  Re: How to Boot with LVM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2015-09-06 22:40 +0200
    Re: How to Boot with LVM ray <ray@aarden.us> - 2015-09-07 02:30 +0200
      Re: How to Boot with LVM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2015-09-07 10:40 +0200
        Re: How to Boot with LVM ray <ray@aarden.us> - 2015-09-08 01:50 +0200
          Re: How to Boot with LVM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2015-09-08 12:40 +0200
            Re: How to Boot with LVM ray <ray@aarden.us> - 2015-09-08 14:00 +0200
              Re: How to Boot with LVM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2015-09-08 15:00 +0200
  Re: How to Boot with LVM Rick Thomas <rbthomas@pobox.com> - 2015-09-07 13:20 +0200
    Re: How to Boot with LVM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2015-09-07 14:40 +0200
    Re: How to Boot with LVM ray <ray@aarden.us> - 2015-09-08 02:00 +0200
      Re: How to Boot with LVM ray <ray@aarden.us> - 2015-09-08 03:40 +0200
        Re: How to Boot with LVM ray <ray@aarden.us> - 2015-09-08 14:10 +0200
          Re: How to Boot with LVM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2015-09-08 15:10 +0200
            Re: How to Boot with LVM ray <ray@aarden.us> - 2015-09-09 04:00 +0200
              Re: How to Boot with LVM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2015-09-09 21:10 +0200
                Re: How to Boot with LVM ray <ray@aarden.us> - 2015-09-10 02:40 +0200
                Re: How to Boot with LVM Pascal Hambourg <pascal@plouf.fr.eu.org> - 2015-09-10 17:00 +0200
                Re: How to Boot with LVM ray <ray@aarden.us> - 2015-09-12 04:30 +0200
                Re: How to Boot with LVM ray <ray@aarden.us> - 2015-09-12 05:10 +0200
                Re: How to Boot with LVM ray <ray@aarden.us> - 2015-09-14 02:40 +0200
                Re: How to Boot with LVM David Wright <deblis@lionunicorn.co.uk> - 2015-09-10 18:10 +0200
                Re: How to Boot with LVM ray <ray@aarden.us> - 2015-09-12 05:10 +0200
      Re: How to Boot with LVM Rick Thomas <rbthomas@pobox.com> - 2015-09-08 10:50 +0200
        Re: How to Boot with LVM ray <ray@aarden.us> - 2015-09-09 04:10 +0200

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