Powering lots of HDDs in server build

Need to power 9 HDDs

[mack]

I am in the process of upgrading my network server. My current server is basically an old PC with a slight hardware upgrade and a homemade drive caddy to hold 4 x 1TB HDDs. I built this about a year ago to provide some additional network storage. It is mainly used for supporting a hobby (video creation).

I have now reached the stage where drive space is becoming limited so I want to expand. This time I don't really want to down the "bandaid" route of hacking something together that "will do" I want to build a custom solution from the ground up.

I plan to use a 4U server case with support for 15 HDDs. I initially will add 8 x 1TB drives. In a raid 5 configuration, this will allow for approx 7TB of usable storage under raid 5. I will use a small SSD for the system/boot disk that will run Ubuntu Server 20.04 LTS.

The motherboard will be a consumer-level AM4 motherboard running a low-end Ryzen CPU and probably 8 gigs of DDR4 ram. This system will only be used for storage, so will not be doing any heavy lifting or number crunching. I won't even be running GPU because it will be running as a headless server in a backroom.

I will install an 8 port PCIe to SATA adapter for all drives within the raid array. The system disk will simply to plugged into an onboard SATA connection.

From the Western Digital Datasheet...

Average power requirements (W)
12VDC ±10% (A, peak) - 1.75
Read/Write - 4.8
Idle - 3.1
Standby - 0.6

If I take the highest value of 4.8 and round it up to 5 (cautious) the total amp draw will be 45 (5x9) amps...
@12v DC that would be 45x12 = 540 Watts

Allowing for a basic system with this disk array attached I would tend to use a 750 Watt PSU. Most ATX style power supplies come with 2 rails for SATA connections and usually have three connections per rail. How would you connect the drives?
My thinking is to add extenders to both of them to have 5 connections on one cable (one going to system SSD) and 4 on the other. The big question is can a single SATA power rail safely and reliably offer around 270 Watts?

There is also the question of power-up. Do disks tend to draw more amps when they spool up at the system start?

I have emailed a few manufacturers and am still waiting for a reply. Datasheets tend to provide total amps and wattage and not per specific rail or line.

Any input would be very much appreciated, specifically from anyone who has done something similar.

Mack.

[engine]

Interesting.

A big question to ask is why you want to do this when you could have a hosting company take all the risks and hassle?

Yes, you could spin up the hard drives as required to save energy as they will require more power at startup. Depending upon the type of drive, some require more energy than others, and it may be three-times the running power.
Some drives are more efficient if they are left on.

I would not skimp on the power supply. Over-rate it or you'll be stressing the components, generating heat and reaching the MTBF earlier than normal.

[lammert]

Hardware RAID or software RAID? With hardware RAID, try to use enterprise HDs. These disks have a different BIOS which doesn't retry in case of a read/write-failure. Instead early on they send an error back to the RAID controller and let the controller figure out what to do using the other drives. This will reduce hiccups when drive errors occur. For the same reason, never use enterprise HDs in a computer without RAID configuration. An enterprise HD may fail where a desktop grade HD will succeed to read the data after a few retries.

Regarding the current, I think you are mixing up Amperes and Watts. The peak current 1.75A is the maximum the drive will ever use. For nine disks this is 16 Amps or roughly 200 Watt on the 12 Volt rail.

[mack]

Thanks Neil...

A big question to ask is why you want to do this when you could have a hosting company take all the risks and hassle?

My broadband speed is the limiting factor. uploading terabytes of anything to the cloud would take weeks. As it stands I can get fast assess to files over ethernet. 4k video files for example are literally huge.

I also like to use Rsync to backup systems. I have a simple process for doing this. I click a button and pop in the server password and it checks what files have been modified or don't exist on the server and uploads/updates accordingly. Long term it will also work out cheaper than paying a hosting provider. There will be an initial cost of hardware, but once it's built and running it's essentially only powered on when being used for a backup or recovery.

you could spin up the hard drives as required to save energy

Within a raid array, the drives are seen as one drive so if any drives are not powered or failed it will result in errors. I could do this to scale the system. Leave a few unplugged until it reaches capacity but every time you add a drive you need to rebuild the array.

I would not skimp on the power supply

Having experienced one going BANG in the past, I agree with that :-)

Mack.

[mack]

Regarding the current, I think you are mixing up Amperes and Watts. The peak current 1.75A is the maximum the drive will ever use. For nine disks this is 16 Amps or roughly 200 Watt on the 12 Volt rail.

I think I read that specification wrong... My understanding is amps is what is provided.. whereas ampers are what a device is pulling?

So far I use software raid configured with MDADM. I don't use enterprise drives because it's a fairly low use system. If it was going to be in use 24/7 then I would need to look at propper NAS drives. Running the current setup (3 drives with software rain 5) I haven't had any issues. Even survived a power outage and hard shutdown...

Mack.

[IanCP]

Why are you limiting yourself to 1 Tb HDD's?

I moved over to 4 Tb some time ago for my video files.

[mack]

Why are you limiting yourself to 1 Tb HDD's?

Mainly cost TBO. The 1TB drives themselves are relatively inexpensive and I already have three but also using 4TB drives would mean losing 4TB of storage in a raid array. 8 x 1TB drives will give me 7TB of usable storage. That should last me a while!

Mack.