Page 1 of 4 123 ... LastLast
Results 1 to 10 of 34

Thread: partition/volume

  1. #1

    Default partition/volume

    (not sure this is the right forum...) So, it looks like BtrFS really wants to create logical volumes. So this is the question I've been g**gling...

    "...and then hard drives (HDs) were created for personal computers, and these HD's had "filesystems" which existed in dedicated on-disk "partitions." The physical disks had up to several "master recordkeeping areas" (MRAs). Then, a limited number of Master Partitions and an Extended Partition (containing "logical drives") could be created, with the information stored in an on-drive MRA..."

    Now, enter LVM* and BtrFS Logical Volumes. How do these relate to logical drives - I assume they're essentially identical except they've been unencumbered by restrictions posed by previous modern filesystems. So, basically, I assume BtrFS has in its structure a place equivalent to what I naively called "MRAs"...
    1. Is that filesystem-config data stored in the MBR/GPT system somewhere or is it in a dedicated BtrFS data-storage area?
    2. What is the main drawback to thinking of a BtrFS 'Logical Volume' as essentially equivalent to a "logical drive?" (...except LV's don't get "mounted" or edited in Partitioner/GParted? Oops - I take that back, they do get mounted... I see them in /etc/fstab looking like separate partitions)

    Of course, there's a TON of technical detail left out of that... but my problem seems to be seeing the "forest for the trees" buried in all the complex online discussions. I basically need to be sure of how to change my backup strategies and applications (dd, clonezilla, etc.).

    Thanks!!

  2. #2
    Join Date
    Jan 2014
    Location
    Erlangen
    Posts
    2,433
    Blog Entries
    1

    Default Re: partition/volume

    Quote Originally Posted by pattiM View Post
    ... but my problem seems to be seeing the "forest for the trees" buried in all the complex online discussions. I basically need to be sure of how to change my backup strategies and applications (dd, clonezilla, etc.).
    Try that first: https://fedoramagazine.org/choose-be...-and-lvm-ext4/
    AMD Athlon 4850e (2009), openSUSE 13.1, KDE 4, Intel i3-4130 (2014), i7-6700K (2016), i5-8250U (2018), AMD Ryzen 5 3400G (2020), openSUSE Tumbleweed, KDE Plasma 5

  3. #3

    Default Re: partition/volume

    Thanks for the great link. I'm reading about bitrot and it makes me want to backup my data and reinstall Opensuse with btrfs to get transparent checksumming. I didn't realize BtrFS had that.

  4. #4

    Default Re: partition/volume

    So it looks like it's "OK" to think of "volumes" in BtrFS as "partitions" that we've dealt with since forever.

    Quick question - back in the days of Lindows, when I first started on Linux - the mantra was "backup your data" - which meant something like: tar -czvf backup.tgz /home/user.

    So, what does "backup your data" mean now with BtrFS? It can be really difficult to deal with a giant tar file, or even a backup manager application, and that difficulty spawns consequential errors for non-gurus. Is "snapshots" (or something else) useful and uncomplicated?

  5. #5

    Default Re: partition/volume

    Oops - I guess bitrot is only automatically fixed (with BtrFS) on a redundant-drive (RAID) setup. Too bad...

    Home computers don't usually have RAID...

  6. #6

  7. #7

    Default Re: partition/volume

    Quote Originally Posted by pattiM View Post
    Home computers don't usually have RAID...
    RAID card is not needed for RAID usage, and sometimes it is wrongful.

  8. #8
    Join Date
    Jun 2011
    Location
    Germany
    Posts
    279

    Default Re: partition/volume

    Quote Originally Posted by pattiM View Post
    ... when I first started on Linux - the mantra was "backup your data"
    For sure it still is.

    Please be aware, snapshots are no substitute for backup! Snapshots are very helpful if you run into trouble with your system. I once ran into a no-space-left problem during the distro upgrade with zypper dup. Seing all the failure messages from zypper I would normally have panicked. But then, I just stopped it, made a rollback to a safe snapshot and freed enough space on the disk. (That included deleting some snapshots, but they weren't the culprit.)
    However, any "real" trouble, i.e. hardware issue and you're lost. If your drive is damaged your snapshots are gone with it. That's why I still keep /home on separate partitions - usually even separate drives. Whatever problem you have with you root system, even if you need a fresh install, change to another filesystem or even hardware, just mount your /home during install. And /home you should backup, of course.
    I have to admit I never used tar for backups. (Not sure, does it compress the archives?). Nowadays disk space isn't the main issue, I'd say. Many people use rsync. There's also dedicated backup software. I'm personally a friend of unison for syncing to my homeserver and from there backing up to other drives including an external hdd.

  9. #9

    Default Re: partition/volume

    I really do like that idea of a snapshot-before-upgrade sort of thing. I also like error correction of bitrot, but that seems to require a RAID setup - I don't know if a snapshot could be used for that but it seems like it would be possible. I think I saw some web pages where people make snapshots (somehow, FULL snapshots) that are moved to another drive (like a USB HD). I'm not sure how that works. BtrFS seems to be changing on an annual bases. So if you could do system snapshots to a USB HD/SSD that would help home computers a lot, since USB3 is quite fast.

    Tar has the option for compression, yes. The "z" in tar -cxvf... uses gzip. Now, the problem I have is that it's difficult to extract single files from a tar file. In fact, I've never succeeded in it due to my misunderstandings of the syntax. So I keep a separate .txt file with the verbose output of tar. That sort of helps. My problem with backup software is its complexity (maybe I'm dyslexic) and difficulty to get rollbacks in the event of a bad system crash.

    Have you ever used dd for a backup? I think you use rsync because it will do incremental backups? People are also talking about dup for correcting errors, although I don't understand how it does that.


    Quote Originally Posted by kasi042 View Post
    For sure it still is.

    Please be aware, snapshots are no substitute for backup! Snapshots are very helpful if you run into trouble with your system. I once ran into a no-space-left problem during the distro upgrade with zypper dup. Seing all the failure messages from zypper I would normally have panicked. But then, I just stopped it, made a rollback to a safe snapshot and freed enough space on the disk. (That included deleting some snapshots, but they weren't the culprit.)
    However, any "real" trouble, i.e. hardware issue and you're lost. If your drive is damaged your snapshots are gone with it. That's why I still keep /home on separate partitions - usually even separate drives. Whatever problem you have with you root system, even if you need a fresh install, change to another filesystem or even hardware, just mount your /home during install. And /home you should backup, of course.
    I have to admit I never used tar for backups. (Not sure, does it compress the archives?). Nowadays disk space isn't the main issue, I'd say. Many people use rsync. There's also dedicated backup software. I'm personally a friend of unison for syncing to my homeserver and from there backing up to other drives including an external hdd.

  10. #10

    Default Re: partition/volume

    dup + BtrFS = error correction ?

    https://zejn.net/b/2017/04/30/single...cy-with-btrfs/
    (Older post...)
    If this works, it would be good for USB backup drives since big ones are cheap... and maybe approximately compensated-for by lzo compression.

    I wonder if there's a way to do these options with Partitioner or GParted?

    Code:
    # mkfs.btrfs --data dup --metadata dup --mixed rpi-btrfs-test.img
    btrfs-progs v4.7.3
    See http://btrfs.wiki.kernel.org for more information.
    
    Label:              (null)
    UUID:
    Node size:          4096
    Sector size:        4096
    Filesystem size:    4.00GiB
    Block group profiles:
      Data+Metadata:    DUP             204.75MiB
      System:           DUP               8.00MiB
    SSD detected:       no
    Incompat features:  mixed-bg, extref, skinny-metadata
    Number of devices:  1
    Devices:
       ID        SIZE  PATH
        1     4.00GiB  rpi-btrfs-test.img

Page 1 of 4 123 ... LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •