[ale] SuSE disk volumes?

Beddingfield, Allen allen at ua.edu
Wed Jan 9 19:28:45 EST 2019 

Yes.  SUSE has done a great job with it.  They've exploited the snapshot 
functionality of it to allow for a rollback feature (updates, for 
example, trigger snapshots).
So...bad update/patch?  Just roll back to the state before it was 
applied (excluding data directories for applications, /home, etc..)
That's the reason for all those mountpoints out of the box.
If your system is really hosed, you can boot from a snapshot, etc...

The upside is the functionality above.  The downside is that all those 
snapshots take a LOT of space over time.  Also, my experience has been 
that filling the "/" filesystem 100% is not something that can be 
recovered from easily.

In most cases, I still use XFS and live without the "benefits" of BtrFS.

Allen B.



On 1/9/19 6:17 PM, Jim Kinney wrote:
> Ah. BtrFS is like LVM thinpool allocation. Allows overcommit on creation 
> to be backfilled later with physical drive space when needed.
> 
> Thus the strange df output as the kernel sees various mounts all with 
> the same size as they are all bit/block-wise COW inode collections.
> 
> On Wed, 2019-01-09 at 17:55 -0600, Beddingfield, Allen via Ale wrote:
>> The "subvolumes" section on this page explains it much better than I can.
>>
>> https://btrfs.wiki.kernel.org/index.php/SysadminGuide
>>
>>
>> Allen B.
>>
>> On 1/9/19 1:22 PM, Jim Kinney wrote:
>>> So a subvolume is sortof partition-like but doesn't actually have a
>>> partition boundary.
>>>
>>> On Wed, 2019-01-09 at 13:15 -0600, Beddingfield, Allen wrote:
>>>> Yeah, that output is horrible.  Essentially you logically define
>>>> whatever you want to be a "volume" for snapshot purposes.  df isn't
>>>> smart enough to tell the difference, so it gives you that mess.  It is
>>>> really one big "/", with subvolumes defined.
>>>> Allen B.
>>>>
>>>> On 1/9/19 1:13 PM, Jim Kinney wrote:
>>>>> Learned something new. Never used BtrFS. That output is rather
>>>>> offputting! What does lsblk show?
>>>>>
>>>>> On Wed, 2019-01-09 at 13:05 -0600, Beddingfield, Allen via Ale wrote:
>>>>>> Not actually a problem - just BtrFS subvolumes.  Look in the
>>>>>> partitioning tool in yast to see the BtrFS configuration.  You may also
>>>>>> want to neuter the snapshot policy, or it will eventually fill up "/"
>>>>>>
>>>>>> On 1/9/19 1:03 PM, Jim Kinney via Ale wrote:
>>>>>>> fun. NOT!
>>>>>>>
>>>>>>> Check for disk errors and copy off anything you care about.
>>>>>>>
>>>>>>> Hmm. That .snapshots folder makes me think that that partition is
>>>>>>> composed (improperly) of files from a previous VM snapshot set that was
>>>>>>> not collapsed before export.
>>>>>>>
>>>>>>> On Wed, 2019-01-09 at 13:39 -0500, Leam Hall via Ale wrote:
>>>>>>>> Am I the only one that thinks this is weird output for "df -h"?
>>>>>>>>
>>>>>>>> ###
>>>>>>>>
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /opt
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /var/tmp
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /tmp
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /.snapshots
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /var/lib/mariadb
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /var/lib/libvirt/images
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /var/lib/pgsql
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /usr/local
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /var/spool
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /var/cache
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /boot/grub2/i386-pc
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /var/crash
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /srv
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /var/opt
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /var/lib/mysql
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /var/lib/named
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /var/lib/mailman
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /boot/grub2/x86_64-efi
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /home
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /var/log
>>>>>>>> /dev/sda2        14G  2.0G   11G  16% /var/lib/machines
>>>>>>>>
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>>>>>>>>
>>>>>>> -- 
>>>>>>>
>>>>>>> James P. Kinney III
>>>>>>>
>>>>>>> Every time you stop a school, you will have to build a jail. What you
>>>>>>> gain at one end you lose at the other. It's like feeding a dog on his
>>>>>>> own tail. It won't fatten the dog.
>>>>>>> - Speech 11/23/1900 Mark Twain
>>>>>>>
>>>>>>> http://heretothereideas.blogspot.com/
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
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>>>>>>
>>>>> -- 
>>>>>
>>>>> James P. Kinney III
>>>>>
>>>>> Every time you stop a school, you will have to build a jail. What you
>>>>> gain at one end you lose at the other. It's like feeding a dog on his
>>>>> own tail. It won't fatten the dog.
>>>>> - Speech 11/23/1900 Mark Twain
>>>>>
>>>>> http://heretothereideas.blogspot.com/
>>>>>
>>>>>
>>>>>
>>>>
>>> -- 
>>>
>>> James P. Kinney III
>>>
>>> Every time you stop a school, you will have to build a jail. What you
>>> gain at one end you lose at the other. It's like feeding a dog on his
>>> own tail. It won't fatten the dog.
>>> - Speech 11/23/1900 Mark Twain
>>>
>>> http://heretothereideas.blogspot.com/
>>>
>>>
>>
> -- 
> 
> James P. Kinney III
> 
> Every time you stop a school, you will have to build a jail. What you
> gain at one end you lose at the other. It's like feeding a dog on his
> own tail. It won't fatten the dog.
> - Speech 11/23/1900 Mark Twain
> 
> http://heretothereideas.blogspot.com/
> 

-- 
Allen Beddingfield
Systems Engineer
Office of Information Technology
The University of Alabama
Office 205-348-2251
allen at ua.edu

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