For me, I wasn’t worried about a spinning disk’s noise so much as I was about optimizing network throughput on my homeserver, but this is what I did…
I installed a 1TB NVME drive in my homeserver and use PrimoCache to get all the things in or out as quickly as possible. I carved a small partition out of the SSD for the OS (Win10Pro), and the remainder is a very fast cache for my storage array. Basically, PrimoCache sits in front of my storage, catches all the writes, puts them onto the ssd, and then writes them to my primary storage later. Subsequently, if any of the cached data is needed, it’s right there on the ssd.
While UrBackup and Plex are thrashing about on the filesystem, the machine doesn’t have to wait for the “slow” spinning disks to read + write, as the operations happen very quickly on the SSD. Exactly how much is cached, whether it’s a read + write cache or either alone, when to write to disk, etc is configurable, but I don’t recall the particulars. You can even have it cache only some of the disks in your storage array, as it doesn’t cache by “drive letter”, but rather by physical disk.
I could have used similar function built into my storage system (Stablebit DrivePool) without PrimoCache, but I’d have to install two SSDs to get DrivePool’s caching to work. Since I only had one NVME slot to install an SSD to, the decision was easy.
By the way… if you’ve got spare RAM, you can let PrimoCache use that for caching, as well, but you better be on a UPS or you risk losing cached data in between writing to the ramdrive and the ssd or spinning rust. Since my network is only 1GbE, I didn’t try out the RAM cache.
Perhaps I should also mention that you can “sort of” do this just by setting your urbackup server to use space on your SSD directly for caching while backing up, but I don’t think you can configure a wait time before writing to disk. I don’t worry about disks spinning all the time. Two years ago I repurposed a 3TB drive out of my homeserver into a UrBackup server for my cousin. It now has about 8 years of power-on time, has zero reallocated sectors, zero pending reallocated, zero uncorrectable errors… you get the picture. I don’t want to turn this into a religious debate, but I’ve had exactly 1 WD drive die in the last decade or more, and that was only because I flashed the wrong firmware update to it. The other brands, I replace them with WD drives when they fail, and never look back.