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Thread: Tumbleweed 20190428 stuck during boot at Assuming write cache: write through

  1. #11
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    Default Re: Tumbleweed 20190428 stuck during boot at Assuming write cache: write through

    Quote Originally Posted by averyfreeman View Post
    plymouth.enable=0 on the boot line worked.

    Thanks, that was most helpful. KDE also loaded as normal, AFAIK. I will edit my grub.cfg to reflect the change.
    No, don't edit "grub.cfg". Edit "/etc/default/grub" or -- better -- use Yast bootloader to make that change.

    If you edit "grub.cfg" the change will go away on the next kernel update (or sooner).

    Do you think I should I submit a bug to bugzilla with my dmesg?
    That's probably a good idea.
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  2. #12

    Default Re: Tumbleweed 20190428 stuck during boot at Assuming write cache: write through

    @Knurpht said "No, snapshots do not work on ext4"


    I tried taking a snapshot with snapper and indeed I get:


    Creating config failed (invalid system type).


    Is there any way to set LVM on the installer to be thin-provisioned?

  3. #13
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    Default Re: Tumbleweed 20190428 stuck during boot at Assuming write cache: write through

    Quote Originally Posted by averyfreeman View Post
    Is there any way to set LVM on the installer to be thin-provisioned?
    I think so. If I can find time tomorrow, I will experiment with that.
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  4. #14
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    Default Re: Tumbleweed 20190428 stuck during boot at Assuming write cache: write through

    Quote Originally Posted by averyfreeman View Post
    Is there any way to set LVM on the installer to be thin-provisioned?
    I experimented with that, today. This was with Tumbleweed 20190502.

    Yes, you can setup thin provisioning during install. But you will need to use the expert partitioner. And you will need to have some prior knowledge about this (which I didn't have).

    My install was to a KVM virtual machine with a 40G hard drive. I configured the VM for UEFI booting.

    I will describe what I did. And, I'll note that my first attempt failed. It looks as if "/boot" cannot be part of a thin provisioned volume. So, for my second attempt, I used a separate "/boot" partition.

    I first created the EFI partition (256M). Then I created a partition for "/boot" (also 256M, format with "ext2").
    I then created a third partition with the remainder of the disk, which I set to be unformatted raw data.

    I then went to the Logical Volume setup of the partitioner.

    The first step was to create a new volume group. I gave it the name "system", and I assigned that third partition to the volume group.

    Then I started creating logical volumes within that group. I first create "swap" at 4G size. I thought it best to keep swap separate from the thin provisioning.

    Next I created a logical volume, which I called "thinpool". I checked the box for a thin pool. And I gave it all remain space in the volume group.

    Next, I created volumes "root" and "home". Since there was no free space remaining, it assigned those to use thin provisioning from "thinpool". I made each 20G. I have no idea what would be a good choice of sizes if the whole purpose is to allow snapshots.

    In any case, that all worked and the system booted.

    No I'm off to report the bug about needing a separate "/boot".
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  5. #15

    Default Re: Tumbleweed 20190428 stuck during boot at Assuming write cache: write through

    Quote Originally Posted by nrickert View Post
    No, don't edit "grub.cfg". Edit "/etc/default/grub" or -- better -- use Yast bootloader to make that change.

    If you edit "grub.cfg" the change will go away on the next kernel update (or sooner)..
    Oh sorry, I meant /etc/default/grub - I kind of meant it as a shorthand for the update from # grub2-mkconfig -o /boot/grub2/grub.cfg

    But thanks for making that explicit, which is what I should have done - it might help someone else.

  6. #16

    Default Re: Tumbleweed 20190428 stuck during boot at Assuming write cache: write through

    Quote Originally Posted by nrickert View Post
    I experimented with that, today. This was with Tumbleweed 20190502.
    I first create "swap" at 4G size. I thought it best to keep swap separate from the thin provisioning.

    Next I created a logical volume, which I called "thinpool". I checked the box for a thin pool. And I gave it all remain space in the volume group.

    Next, I created volumes "root" and "home". Since there was no free space remaining, it assigned those to use thin provisioning from "thinpool". I made each 20G. I have no idea what would be a good choice of sizes if the whole purpose is to allow snapshots.

    In any case, that all worked and the system booted.
    Thin-provisioning swap is interesting from a space usage standpoint, since it could expand/contract as needed, leaving more room for other partitions over-provisioning. Obviously using a separate swap partition with linux swap formatting is preferable from a performance standpoint, though.

    Here's the interesting thing about snapshot sizes, if I read this correctly they have to be pre-configured - I am not sure how that would interact with the ability to over-provision thin volumes. From Redhat https://access.redhat.com/documentat...on/lv_overview

    The size of the snapshot governs the amount of space set aside for storing the changes to the origin volume. For example, if you made a snapshot and then completely overwrote the origin the snapshot would have to be at least as big as the origin volume to hold the changes. You need to dimension a snapshot according to the expected level of change. So for example a short-lived snapshot of a read-mostly volume, such as /usr, would need less space than a long-lived snapshot of a volume that sees a greater number of writes, such as /home.
    If a snapshot runs full, the snapshot becomes invalid, since it can no longer track changes on the origin volume. You should regularly monitor the size of the snapshot. Snapshots are fully resizable, however, so if you have the storage capacity you can increase the size of the snapshot volume to prevent it from getting dropped. Conversely, if you find that the snapshot volume is larger than you need, you can reduce the size of the volume to free up space that is needed by other logical volumes.


    It seems kind of clunky to me compared to CoW FS (still unclear whether thin-lvm is considered a type of CoW FS) but it is definitely a fascinating option. For people who are EXT4 or XFS purists (like RedHat) it offers the ability to have more modern features of CoW FS like snapshots, data-discard, etc. but obviously BTRFS seems superior on the face of it. Over-provisioning seems to be one truly unique feature, I'm not sure if that's available any other way. In any event, no FS is truly "superior", they're all just different, right tool for the job and all that

    Thanks for trying that and explaining how you did it, I really appreciate it!
    Last edited by averyfreeman; 06-May-2019 at 11:11. Reason: meh. still getting used to this clunky forum software.

  7. #17
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    Default Re: Tumbleweed 20190428 stuck during boot at Assuming write cache: write through

    Quote Originally Posted by averyfreeman View Post
    @Knurpht said "No, snapshots do not work on ext4"


    I tried taking a snapshot with snapper and indeed I get:


    Creating config failed (invalid system type).


    Is there any way to set LVM on the installer to be thin-provisioned?
    If you want to create EXT snapshots and have the ability to roll back similar to what you can have on BTRFS,
    I highly recommend the following

    http://extundelete.sourceforge.net/

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  8. #18
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    Default Re: Tumbleweed 20190428 stuck during boot at Assuming write cache: write through

    Quote Originally Posted by averyfreeman View Post
    It seems kind of clunky to me compared to CoW FS (still unclear whether thin-lvm is considered a type of CoW FS) but it is definitely a fascinating option.

    It probably has a different intended usage case than "btrfs" snapshots.

    Perhaps the idea is that you make a snapshot. And then you backup the snapshot. This avoids backing up actively changing files. Once you have made the backup, you can release the snapshot.

    Thanks for trying that and explaining how you did it, I really appreciate it!
    I did learn something about it. And I reported bug 1134130 (that "/boot" cannot be part of a thinly provisioned volume). I'm not sure what they will do about that. My recommendation was to just document the problem and mark as WONTFIX.
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  9. #19

    Default Re: Tumbleweed 20190428 stuck during boot at Assuming write cache: write through

    Quote Originally Posted by tsu2 View Post
    That's not snapshot software, it's file recovery software.

    Thanks for the tip, though.

    Here's some info about snapper+thin-provisioned LVM

    https://www.thegeekdiary.com/how-to-...using-snapper/

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