Need some help with cache drive, VM's, Dockers

[JoshFink]

Hi, I'm sure this is a basic question but I need some help with best practices on how to do some things. 

 

I'm setting up a new unraid (and I'd like to make some changes on my other one) and I'd like to figure out some best practices. 

Currently I have an Unraid setup where I have all of my dockers on my cache drive (1TB SSD) and my configurations in /mnt/user/appdata. I was thinking the other day that if I lost my cache drive I would lose all of my dockers and be out of luck. What is everyone doing with regards to this? Just backing up the appdata folder with the plugin (CA Backup / Restore Appdata) and not worrying about it or is there some kind of way to put in another cache drive and some kind of redundancy? 

 

That question applies to both Unraids that I'm setting up. I also want to run some VM's on the new Unraid. Are people running them on their cache drives or somewhere else? I have two 1TB SSD's I was going to put in as the cache drives. Kind of the same question though. I can put the VM's on the cache drive but are people backing them up other places or running some kind of redundancy? 

 

Reading this I think the terminology I'm using is probably incorrect. Hopefully everyone can get the gist and offer some advice though. Thanks

Edited August 13, 2020 by JoshFink

[trurl]

The default for multiple cache pool is btrfs raid1 mirroring, so if you have more than one drive in a pool then it has redundancy.

 

Use the CA Backup plugin to backup appdata, virt.img, and flash. Flash is the other piece of the puzzle you will need to restore your dockers if there is a problem, since their templates (the mappings, etc.) are on flash.

 

And finally, you don't want appdata, domains, system shares on the array, because docker/VM performance will be affected by slower parity updates, and because they will keep array disks spinning due to open files.

[JoshFink]

Thanks @trurl for the response. I have a couple of more questions if you wouldn't mind. 

 

1 hour ago, trurl said:

The default for multiple cache pool is btrfs raid1 mirroring, so if you have more than one drive in a pool then it has redundancy.

Thanks. So, in your opinion, is redundancy even needed for this or does it make sense to leave it on one and just back it up? 

1 hour ago, trurl said:

Use the CA Backup plugin to backup appdata, virt.img, and flash. Flash is the other piece of the puzzle you will need to restore your dockers if there is a problem, since their templates (the mappings, etc.) are on flash.

If I understand this correctly, it makes sense to set my 'appdata source' in CA Backup to be /mnt/user and then exclude everything but appdata and system. Flash I've always backed up manually. Is there a way to do it with the CA Backup plugin? 

 

BTW, I'm assuming by virt.img you mean libvirt.img in the system/libvirt directory, is that correct?

1 hour ago, trurl said:

And finally, you don't want appdata, domains, system shares on the array, because docker/VM performance will be affected by slower parity updates, and because they will keep array disks spinning due to open files.

This one I understand. However, how can I change my appdata, domains and system shares to be on the cache rather than where they are stored now and not lose anything? I can obviously manually move them but how would I tell unraid where they are now located? 

 

This is probably pretty easy but I can't wrap my head around this. Thanks again for the help.

[trurl]

10 minutes ago, JoshFink said:

If I understand this correctly, it makes sense to set my 'appdata source' in CA Backup to be /mnt/user and then exclude everything but appdata and system. Flash I've always backed up manually. Is there a way to do it with the CA Backup plugin? 

No, just make your appdata source your appdata and only backup appdata that way. There is never any need to backup docker.img since it is only the executable code for the installed dockers and these are easily downloaded again. CA Backup also has a provision for backing up flash and libvirt.img.

 

14 minutes ago, JoshFink said:

This one I understand. However, how can I change my appdata, domains and system shares to be on the cache rather than where they are stored now and not lose anything? I can obviously manually move them but how would I tell unraid where they are now located? 

The usual way is to let mover take care of moving these cache-prefer user shares to cache. That is what cache-prefer means, prefer to keep these on cache.

 

However, mover can't move open files, so you will have to disable Docker and VM Services (Settings - Docker and Settings - VM Manager) before going to Main - Array Operation to Move.

 

You can see which disks each User Share is using by clicking on Compute... for the share.

 

Post diagnostics if you want more detailed advice.

[trurl]

1 hour ago, trurl said:

Flash is the other piece of the puzzle you will need to restore your dockers if there is a problem, since their templates (the mappings, etc.) are on flash.

Another note about this. In order to get your templates reused, you must use the Previous Apps feature on the Apps page. If you just try to install a docker without using Previous Apps, you will get a fresh template for that docker.

[JoshFink]

Awesome. Thanks for the help @trurl