On 12/30/2015 10:14 PM, lee wrote: > Hi, > > soon I'll be replacing the system disks and will copy over the existing > system to the new disks. I'm wondering how much merit there would be in > being able to make snapshots to be able to revert back to a previous > state when updating software or when installing packages to just try > them out. > > To be able to make snapshots, I could use btrfs on the new disks. When > using btrfs, I could use the hardware RAID-1 as I do now, or I could use > the raid features of btrfs instead to create a RAID-1. > > > Is it worthwhile to use btrfs?
Yes. ;-) > Am I going to run into problems when trying to boot from the new disks > when I use btrfs? Yes. ;-) well ... maybe. prepare for some learning curve. but it is worth it! > Am I better off using the hardware raid or software raid if I use btrfs? I would be picky here and separate "software raid" from "btrfs raid": software raid .. you think of mdadm-based software RAID as we know it in the linux world? btrfs offers RAID-like redundancy as well, no mdadm involved here. The general recommendation now is to stay at level-1 for now. That fits your 2-disk-situation. > The installation/setup is simple: 2x3.5" are to be replaced by 2x2.5", > each 15krpm, 72GB SAS disks, so no fancy partioning is involved. > > (I need the physical space to plug in more 3.5" disks for storage. Sure > I have considered SSDs, but they would cost 20 times as much and provide > no significant advantage in this case.) > > > I could just replace one disk after the other and let the hardware raid > do it all for me. A rebuilt takes only 10 minutes or so. Then I could > convert the file system to btrfs, or leave it as is. That might even be > the safest bet because I can't miss anything when copying. (What the > heck do I have it for? :) ) > > > Suggestions? I would avoid converting and stuff. Why not try a fresh install on the new disks with btrfs? You can always step back and plug in the old disks. You could even add your new disks *beside the existing system and set up a new rootfs alongside (did that several times here). - There is nearly no partitioning needed with btrfs (one of the great benefits). I never had /boot on btrfs so far, maybe others can guide you with this. My /boot is plain extX on maybe RAID1 (differs on laptops/desktop/servers), I size it 500 MB to have space for multiple kernels (especially on dualboot-systems). Then some swap-partitions, and the rest for btrfs. So you will have something like /dev/sd[ab]3 for btrfs then. Create your btrfs-"pool" with: # mkfs.btrfs -m raid1 -d raid1 /dev/sda3 /dev/sdb3 Then check for your btrfs-fs with: # btrfs fi show Oh: I realize that I start writing a howto here ;-) In short: In my opinion it is worth learning to use btrfs. checksums, snapshots, subvolumes, compression ... bla ... It has some learning curve, especially with a distro like gentoo. But it is manageable. As mentioned here several times I am using btrfs on >6 of my systems for years now. And I don't look back so far. - look up: https://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices
