Re: [gentoo-user] [OT] SMR drives (WAS: cryptsetup close and device in use when it is not)

[William Kenworthy]

On 2/8/21 5:55 am, Frank Steinmetzger wrote:
> Am Sun, Aug 01, 2021 at 11:36:36AM +0800 schrieb William Kenworthy:
>
>>>> Its not raid, just a btrfs single on disk (no partition).  Contains a
>>>> single borgbackup repo for an offline backup of all the online
>>>> borgbackup repo's I have for a 3 times a day backup rota of individual
>>>> machines/data stores
>>> So you are borg’ing a repo into a repo? I am planning on simply rsync’ing
>>> the borg directory from one external HDD to another. Hopefully SMR can cope
>>> with this adequatly.
>>>
>>> And you are storing several machines into a single repo? The docs say this
>>> is not supported officially. But I have one repo each for /, /home and data
>>> for both my PC and laptop. Using a wrapper script, I create snapshots that
>>> are named $HOSTNAME_$DATE in each repo.
>> Basicly yes: I use a once per hour snapshot of approximately 500Gib of
>> data on moosefs, plus borgbackups 3 times a day to individual repos on
>> moosefs for each host.
> So you have:
> Host A ──[hourly]──> Online-Borg A ─┐
>                                     ├──[3/day]──> Offline-Borg
> Host B ──[hourly]──> Online-Borg B ─┘
> ?
>
>> 3 times a day, the latest snapshot is stuffed into a borg repo on moosefs
>> and the old  snapshots are deleted.
> How do you stuff just the latest snapshot of a repo into another repo?
>
>> 3. borgbackup often to keep changes between updates small - time to
>> backup will stay short.
> Apparently you are dealing with some kind of productive, high-availability
> or high-throughput system. I only have my personal stuff, so I don’t mind it
> taking a few minutes. That allows me to watch progress bars and numbers
> going up. :)
>
>> 4. borg'ing a repo into a repo works extreemly well - however there are
>> catches based around backup set names and the file change tests used.
>> (ping me if you want the details)
> But what is the point of that? Why not simply keep the last x hourly/
> daily/weekly snapshots? The only thing I can think of is to have a
> small(ish) short-term repo and keep the larger archival repo separate.
>
Hi Frank,

Not quite - I see I could have been clearer.  I "experiment" a lot -
which means things break so I need to get back running quickly.  So the
purpose of the online repos and snapshots is just for that - quick
recovery.  Longer term I want to have an offline copy for a real
disaster (yes, I have needed to restore almost 20TiB including the
online backups on the moosefs system three months ago - self caused :)
as well as often needing to step back a few days/weeks for a historical
copy of a file, or less often a system restore on a host.  By the way,
this discussion has been useful as I found some failed backups due to a
missing dependency in the borgbackup ebuild when looking closer at it -
has a bug.  Need to do some watcher scripts to detect that.


stage 1: online, immediately available

Hosts (those with actual attached storage - a mixture of intel, arm32
and arm64 devices are backed up to their own borg repo 3 times a day via
push.  One repo per machine on moosefs.

A separate script does an hourly backup of VM, LXC images, and various
data stores via a moosefs snapshot.

stage 2: resource management for the snapshots

3 times a day, a script does a borg create on the latest snapshop at the
time, and when complete deletes all previous snapshots (-1) so at that
point I have two older snapshots available + a couple created during the
borg run - note that large multi GiB snapshots can quickly use up all
memory (32GiB) on the moosefs master unless culled regularly.

stage 3: offline because disasters happen :)

All borg repos are on moosefs with a single root directory
(/mnt/mfs/backups) so once every day or so I manually mount the offline
disk and do a borg create on the backup directory.  I was doing this
once a week, but operationally its easier to do 5-10 minutes every day
than an hour once a week due to the scale of changes over the longer
time period.

So, its looks like:

Host A    ──[3/day]──> Online-Borg A   ─┐
                                        ├─────────────────────────[common directory]---[manual, 1/day]──> Offline-Borg
Host ...  ──[3/day]──> Online-Borg ... ─┘                             |
?                                                                     |

Snapshots ──[hourly]──> Online-Borg "snaps" ─[3/day] ─────────────────┘ 


BillK