# Migration Geodesic ZFS

----

# Needs
![intro](./assets/intro.png =500x)

----

# Summary
- Rsync
    - Offline migration (data files)
    - Online migration (dumps)
- Snapshots
    - Virtual Machines
    - ZFS/BTRFS
    - Container-based solutions

----

## rsync/scp : offline migration

![rsync 1](./assets/rsync_1.png)

----

## rsync/scp : online migration
![rsync 2](./assets/rsync_2.png)

----

## rsync/scp
#### Possible practical issues :
- File permissions
- Postgres permissions
- SSH keys
- Configuration mismatch

<!--- Static files : `rsync` or `scp` --->
```diff
+ No big architectural changes
- Lots of configuration
- Heavy : will take time to backup and restore
- Hacky ?
```

----

## Snapshots

![gitflow1.svg](./assets/gitflow1.svg =100%x)

----

## Snapshots

![gitflow2.svg](./assets/gitflow2.svg =100%x)

----

## Snapshots

![gitflow3.svg](./assets/gitflow3.svg =100%x)

----

## Snapshots

![gitflow4.svg](./assets/gitflow4.svg =100%x)

----

### Virtual Machine cloning
```diff
- Must fiddle with hypervisor
- We don't want to nest virtual machines
```

----

### ZFS
<!-- https://cdn.arstechnica.net/wp-content/uploads/2020/05/copyonwrite-000-nocow.gif -->
![cow.gif](./assets/copyonwrite-000-nocow.gif)
> Conventional Filesystem

----

### ZFS
<!-- https://cdn.arstechnica.net/wp-content/uploads/2020/05/copyonwrite-000-nocow.gif -->
![cow.gif](./assets/copyonwrite-001-data-comet.gif)
> Copy on write (CoW)

----

### ZFS
<!-- https://cdn.arstechnica.net/wp-content/uploads/2020/05/copyonwrite-002-data-worm.gif -->
![cow.gif](./assets/copyonwrite-002-data-worm.gif)
> Simplified CoW representation

----

### ZFS
<!-- https://cdn.arstechnica.net/wp-content/uploads/2020/05/copyonwrite-003-visualizing-snapshots.gif -->
![cow.gif](./assets/copyonwrite-003-visualizing-snapshots.gif)
> Snapshots using CoW

----

### ZFS
#### Tools : 
- [zrepl](https://zrepl.github.io/quickstart.html)
- [syncoid](https://github.com/jimsalterjrs/sanoid/wiki/Syncoid)
```diff
+ Automatic / Seamless
- Possible use of untested additional tools/programs
- Additional system complexity 
```

----

### Container-based solutions
#### LXD
- Hypervisor for Linux Containers (LXC) and virtual machines
- Can use ZFS
- Canonical maintaned


```diff
+ Automatic / Seamless
- Additional architectural complexity 
```

----

#### Kubernetes Volume Cloning

```diff
+ Automatic / Seamless
- Additional architectural complexity 
- Definitely Hacky
- Kubernetes
- Better handled with operators/pods
```