I'm currently working on getting my thoughts together for the very low power, very high capacity offsite storage solution and something I wanted to talk about is how important of a feature Staggered spin-up can be as I don't believe I'll have it so it's possible I'll have to change my plans.
As I've disassembled a small system I had idling doing nothing I've scavenged it's Corsair SF450. It's an 80 Plus Gold SFX form factor PSU. Tiny little thing. I can make a SFX to ATX bracket on the 3D printer so this would save me the money of buying a PSU for this server. However, that really depends. And this is where staggered spin-up is a desirable feature.
The motherboard I plan to use is the ASRock Rack C2750D4I it's Mini-ITX and uses three separate SATA controllers:
QuoteIntel® C2750 : 2 x SATA3 6.0 Gb/s, 4 x SATA2 3.0 Gb/s
Marvell SE9172: 2 x SATA3 6.0 Gb/s, support RAID 0, 1
Marvell SE9230: 4 x SATA3 6.0 Gb/s, support RAID 0, 1, 10
I plan to occupy 9 or all 12 of those ports.
The drives I'm currently planning to go with are the Seagate Ironwolf NAS 10TB 7200RPM drives. Looking up their data sheet:
Each drive will pull about 1.97A @ 12V & 0.58A @ 5V on initial spin-up (on the DC side of the PSU - worse on the AC side). This means for a total of 12 drives for all of them to spin-up at once I need to account for a minimal potential current draw of almost 24A @ 12V & 7A at 5V. My little SF450 can do 37.5A & 20A respectively so I should be OK but just barely as I have to account for all the other hardware in the system.
I plan to control the RAID with ZFS and I only plan to SSH in and update this backup on a 24hr basis so using S.M.A.R.T. I'll have the drives spin down when not in use as they won't be for most hours of the day. Hopefully S.M.A.R.T. is smart enough to stagger the spin-up. If not I'll be pulling all those Amps every time the pool needs to spin-up.
And that's only 12 drives. Imagine 30/45/60+ (~60A/~90A/~120A) staggered spin-up gets to be an important feature as you scale up.
