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
