Synology DS920+ Basic Setup and Upgrade Questions

[justwondering 14]

I just bought a Synology DS920+ four bay NAS to replace my existing system: a Raspberry Pi 4 with four WD EasyStore external HDDs connected by USB. Two drives are Emby media libraries and two are backups of those media libraries, maintained with a nightly rsync. My plan is to shuck the drives and add them to the NAS in the same roles, and run Emby straight from the DS920+.

My requirements are pretty basic: I'll be using this exclusively for a family media server, so I'm not planning on running anything on it but Emby and basic file sharing. All my video is H.264 MP4s, so it shouldn't be doing any transcoding. Most of my videos are 1080p, although I've got some larger ones for VR (Oculus) and I may start accumulating 4k in the future. The NAS will be plugged directly into my wifi router, and all the clients (mostly Apple TVs and phones) attach by wifi. Probably it will never see 4 simultaneous streams, but I'd like it to be able to handle that.

Seems simple in principle, but I have a bunch of questions!

1. My drives are all pure media in EXT4 format, so if I ever want or need them out of the NAS I can plug them into virtually any other computer. Can I keep them like this in the NAS or do I need to let it reformat them to Synology's proprietary format (Btrfs)?

2. I'd prefer to keep just media on the big slow HDDs. Can the NAS boot drive be either an external USB or one of the M.2 NVMe slots?

3. Emby pre-downloads and pre-generates images and metadata and video previews and stores them in the same directory as the media. I could moved all that to an SSD (either USB or NVMe). Or I could install and NVMe SSD and use Synology's built-in caching. Or I could just leave the metadata where it is. Is it likely to make a noticeable difference in terms of menu snappiness? If so, what's the preferred solution?

4. Do I have to recreate all my Emby settings, media libraries, etc.? Or is there an easy way to migrate all that over?

5. I've been backing up my media by dedicating half my drives as backups and doing a nightly cron rsync. Is there a smarter way to do it?

I know there's a ton of experience here so I would appreciate any help or advice you guys can give me. Thanks!

[Carlo 4561]

You are giving up the main reason to use a NAS in your current setup.  One of the main advantages of a NAS is the built in RAID with at least a single parity drive.  Ideally with 4 drives you would use all four in a RAID 5 type array which gives you 3 disks of storage and 1 drive for parity/protection.

You would then back things up to a network location or USB3 based set of drives.

Without playing tricks with the OS the NVMe slots are only available to use as a read cache (1 slot) or read/write (2 identical slots used). This does help, but we have been testing some alternative ways to set things up when using the NAS primarily for Emby. I've been doing these tests on a DS920+ myself and will have this written up hopefully within the week.  So for now I'd skip any thoughts of NVMe use.  Just a FYI: the read/write cache mechanism can only be used if you have setup an array using btrfs.

What you're asking about putting the cache and metadata on the NVMe drives isn't possible with normal Synology use (only read or read/write caching) but is something that can be done from the command line using a custom setup which will be documented shortly after a bit more testing.

[justwondering 14]

Hi cayars, thank you for your help.

I should have specified in my original post that my four drives are two mismatched pairs: a pair of matching 10 TB drives a pair of matching 14 TB drives. So if I understand right (dubious) I could still do RAID 5 but I wouldn't be able to use the full size of the larger drives. So I could get ~ 30 TB of RAID 5, vs 24 TB using them as plain old drives. Would you still recommend RAID 5 for this situation? Or would it be OK to use them as plain old hard drives for now, and plan to eventually buy two more 14 TB drives and switch the whole thing to RAID 5 when I need the space?

Sounds like for now I should just leave the NVMe slots alone and wait for your testing and writeup.

I notice you didn't address the possibility of having the NAS boot from NVMe or external USB drive. Does that mean it's totally impossible? Or not recommended for some other reason?

Thanks for your help!

[Carlo 4561]

Mine is mismatched as well but with 3 14TB drives and 1 18TB drive.

So here's my NAS:

And here's yours:

I choose two types of RAID arrays based on best results.  The pure RAID 5 works out to be smaller for both of us while the SHR (Synology Hybrid Raid) is larger.
In this you're not really loosing out at all with SHR except that one of the larger drivers is used for parity.

These numbers are raw storage numbers.  As an example looking at mine above I have 44 TB of usable space.  Let's convert that to TiB by diving by 1024 and then multiplying by 1000.
44/1024*1000=42.96.  Now let's multiple that by 89.5% or .9 which will take into consideration the partitions, formatting, file allocation tables and other things leaving me with:
38.46 TiB of usable storage.

That number is pretty close to what Synology shows which is 38.2. you'll see below:
 

Now looking at your NAS with 34 TB of raw usable space.
34/1024*1000*.895=29.7 TiB of storage would sound just about right.

So between the choices of SHR and RAID 5, SHR is going to be the more flexible and easier to upgrade solution.

Hope that helps,
Carlo

 

[justwondering 14]

Thank you for the great analysis! I'm convinced - I'll try out SHR.

The only real downside I can see is that if the DS920 itself ever fails, I'll need another Synology box to get my data out.

[Carlo 4561]

Nope, you can put all drives in a PC running Ubuntu Linux and mount them.

I've actually done this myself just as a test.  I then wrote about 10TB to the array, unmounted it. Put drives back in 920+ and boom, mounted back in Synology with the new info.