[Brad]

Originally Posted by Yontsey Question is, how many HDDs should I get initially and how big? My externals right now are 8TB but I had some room to grow. I can't remember exactly how much off hand. If I go with 2 8TB and set them up in SHR, that will give me one for storage and one for backup, correct? If I have 4 8TB would that be 16TB storage and 16TB backup?

SHR with just two drives means they're basically mirrored. So, two 8TB drives gives you ~8TB of usable space.

However, if you start with more than two drives, instead of mirroring, SHR will stripe the data with "parity" data across the drives. In that configuration, less than half of the total storage will be used for parity (data integrity). Four 8TB drives would give you ~24TB of usable space. The math gets weird quickly if you mix drive sizes, but if they're all the same size, then you basically "lose" roughly one's worth of capacity to store parity data.

When in doubt, Synology's website has a good calculator GUI here: https://www.synology.com/en-us/support/RAID_calculator . Click the drive sizes at the top to add them to the NAS below, or click the drives in the NAS to remove them. Then scroll down to see the effect those changes have on available storage.

Originally Posted by Yontsey one for backup, correct?

Rule number one of RAID: RAID is NOT a backup. Having multiple drives in a RAID-like configuration that uses mirroring or parity will provide you some read performance gains and can self-heal against bitrot or keep things running with degraded performance if you have one failing drive, but if you accidentally delete a file, it's immediately deleted from the mirror/parity as well. This is why storage gurus are adamant not to call RAID (or SHR or XFS) a "backup". It can be mirrored or have parity data, but it's best to pretend like that doesn't exist because you will never interact directly with it.

You gotta treat the NAS as one big hard drive. If there's anything mission-critical in there, you still want periodic backups to an external device. You may find lots of resources talking about the 3-2-1 backup rule or strategy (and I may have mentioned it earlier in this thread). One good summary from Seagate's blog here: What is a 3-2-1 Backup Strategy?

The 3-2-1 rule, attributed to photographer Peter Krogh, follows these requirements: • 3 Copies of Data – Maintain three copies of data—the original, and at least two copies. • 2 Different Media – Use two different media types for storage. This can help reduce any impact that may be attributable to one specific storage media type. It’s your decision as to which storage medium will contain the original data and which will contain any of the additional copies. • 1 Copy Offsite – Keep one copy offsite to prevent the possibility of data loss due to a site-specific failure.

That may be overkill depending on your needs, but at the very least, having a disconnected external drive that's periodically updated with a backup of your NAS's contents will put you light years ahead of most, and that'll give you an actual backup you can load in case you accidentally delete something from your NAS.

So, if you want 16TB of usable storage with a backup, you want at least three 16TB drives. Two 16TB drives go in the NAS, and one 16TB drive stays outside for periodic backup.

Originally Posted by Yontsey Once again, forgive my lack of knowledge.

Hey, we all have to start somewhere! When I started this thread, I was basically in your shoes. I had several external USB drives. I'd read a bunch of articles and wikis and watched some YouTube videos, but I'd never actually put my hands on a NAS before.

Speaking of new NASes, my DIY NAS has been rock solid for the last couple months and performance continues to be great. I've decided that I probably won't be buying a Synology NAS any time soon, at least as long as this old hardware keeps chugging along. I have used its Docker/Kubernetes capabilities a few times, and I have a long-running container for my media in Jellyfin (basically FOSS Plex), but I haven't needed to do anything with full VMs, and I doubt I will.