Very interesting project, spurred me into resurrecting an old N54L. Can I ask you gentlemen what's the highest capacity HDD you've managed with this? I've read somewhere there was no limit but has anyone tried using 8TB or 10TB drives? If so, what brand/models. Thanks in advance.

A post just in time since I wanted to upgrade my HP Microserver, but liked the form factor.

I made things a little different :

- I removed the old motherboard and the led and power-on switch assembly, and keep them apart (just in case...)

- I replaced the base of the NUC by two 1/2" aluminum angle, in order to have the same width as a CD reader. I then used a few inches of double adhesive tape and the metal spring that are on one side of the CD cage to fix it firmly enough. The front end of the NUC is just outside the face of the Microserver. So I had every socket at hand.

- the NUC is powered by the socket on the former CD power cable.

- I didn't use a adapter, but made an RJ45 cable pass through the former VGA plug hole (I only need one Ethernet port), since I only need a meter long cable to the internet box.

- I soldered a three wire adapter (to send 5V to the fan, it's enough) and a switch (to power on/off the PSU) on an salvaged motherboard power socket. The switch is fixed on one of the remaining holes at the end of the Microserver, so I can easily turn off the power to the disks

- last but not least, I used the protection foam of the NUC packaging to block the front grid under the hard disks cage and the original PSU.  The air is then forced through the disks and around the NUC only. The NUC is totally cold even when using heavily the server.

Nice! A quicker hacked together solution, but I bet it still lasts until the next upgrade! 

Did you block the entire front door with foam? Because wouldn't that stop the HDDs from getting any airflow?

Just the bottom is blocked, so HDD are still ventilated : I put the foam under the HDD cage and on the side, under the PSU, so it is also in the airflow. I can feel the air passing on top of the NUC and in front of the HDD, so it's OK.

Unfortunately, I didn't see a mean to add a picture...

Oh yeah, that makes sense!

Thanks for the inspiration - I went slightly differently:

- Removed PSU

- Removed motherboard

- Located the NUC in the bottom of the case - it's cooler down there and fits easily.  I didn't like the idea of putting it up top since it's warmer and also this way I didn't need to make any new vents as airflow naturally pulls over the bottom of the case (which is what HP relied on originally).

- Modded to use a PicoPSU + laptop brick externally

- Took the 12v in to both the PicoPSU + the NUC 

- Added a 5v relay with a USB input - this is powered by the NUC and signals the PicoPSU to power up (by joining two pins) which in turn powers on/off the hard disks plus case fan.  I used a ready made opto isolated PCB which cost a couple of quid.

- For now I've hard wired the case fan at a lower voltage but I plan to add a USB driven fan controller to allow the NUC to vary it.

- I'm also going to mod the case lights and power button but for now I can simply open the front door and press the NUC's switch.

I also added some panel connectors on the back to allow me unplug ethernet etc easily.  I'm almost done putting it back together today.

That's cool! Have you got any pics? The airflow through the drive bay when it is open at the front like mine is more than the airflow across the drives. So cooling is probably better up top. But I think it doesn't really matter because the N100 is so low power. Almost any air moving would keep it cool!

Did you use the same mini pc as mine (in the pics)? Because the CPU is mounted to the 'top' of the case but the mini SAS needs to connect to the bottom I didn't think I could fit it in the bottom of the Microserver where the original mobo went. I didn't want to push the heatsink of the mini PC right down against the bottom of the case.

I was going to use a flip flop latch PCB to get the original power button to turn on/off the PSU but tbh it's so rare for me to power it off that it wasn't really worth the effort!

Is the picoPSU doing anything other than 12->5v conversion for the sata power of the drives? I did think of powering the whole thing from a 12v brick with a cheap DC-DC board for 5v but good 12v bricks aren't very cheap. And I've had a few die on me. Might do it anyway if/when my internal PSU dies.

I didn't really make any pics (which I regret).   Heat rises but you're right it will make little difference as the fan will move air OK.  I did notice the box was warmer up top pre-mod as by default there is no vent up there (and you put one in). 
The bottom of the case is a big sheet of (cool) metal but the mini PC I'm using sits on feet and has good air vents around it.  Additionally I've left the top of the mini PC case off because the SAS cable needs to go through and also because this helps with ventilation (plus, hey, it's in a bigger case now anyway).  The mini PC I used was the GMKtec G3 which I got for a good price.  I removed the SSD that came with it in order to fit the SAS card and used the other slot to fit a small form factor SSD.  The G3 - and I really mean this - *just* fits in with some wiggling.  Having the top off helped!   I got lucky here as this could of been a deal breaker and forced me to look at the top of the case instead.  

For power I've set up windows to be remotely shutdown (button on my smart home setup plus an automation that triggers shutdown if mains voltage in the house drops - it's on a UPS but not able to monitor it) and in reverse I can power it up with a WOL packet even from off state.   Since it sits somewhere out of the way this is works perfectly.  As I got windows with it I went with it as everything worked fine and it gives me some flexibility if I want to run other stuff at a later stage.  If I went multi-use I might consider proxmox as I've done that elsewhere on another mini PC.  I'm collecting the darn things..

The picoPSU:  I did this mod many years ago due to the noise of the built in PSU and it was a popular mod.  In other words I had the power brick and PSU already so it was a obvious mod to have it power both the NUC and the unit itself (in this case the drives plus the rear fan).  I had (I'm a hoarder) a quiet 120mm fan lying around so I changed this out as the delta fan is mental without regulation.  Again I had a fan speed controller (just a rheostat with a knob) kicking around so I used this tune the fan to a speed where the noise was in a happy space.  This means I've got fixed airflow but, relatively speaking, that's what happened before as the unit sits idle almost all the time.  The mini PC has it's own fan too and I'm not seeing that spin up and good temps all round (PC + drives).   The pico PSU and brick have lasted over 10 years I would guess :D 
The relay I used (test them as they are cheap as heck): https://www.amazon.co.uk/gp/product/B07PRPKMK6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I kinda like mechanical relays cos they go CLUNK when powered :)  It's not a perfect choice given it will eventually wear out versus a solid state one but it's a cheap viable solution given it will switch maybe 100 times ever.  The relay module and picopsu I just hot glues to piece of plastic (food container top) and put behind the mini PC at the bottom of the case.  This was really just to group them but also make sure they couldn't short on the metal.  It's ghetto but it's reversible and works (and again it's all in a case).

I picked up a USB to motherboard style header connector so I can route one USB to the front panel which may be handy at some point but I'm in no rush to fit it.

Thanks for the explanation! Yeah re-using already obtained kit is high on my list of priorities so makes sense to re-use what you had. I also did a fan swap when I first got the Microserver, I also fan swapped the PSU because as you said the original was noisy. I've also fixed the rear fan speed - the only issue I have with the lower rear fan speed is dust buildup on the intake. Needs a clean once a year. You're right the top of the unit gets warm in the stock configuration but is cool now with my mod.

I didn't consider those mini PCs might be semi fanless, that should be good for extending the life of the cheap fan if it is mostly not spinning up!

I thought my mini PC came with an internal USB header so I intended to connect up the front panel USBs, but unfortunately the listing was a little misleading and it was actually a serial port header. I could use an internal adapter but given the mini PC ports (incl usb3) are accessible  behind my new door, I don't think I need to now.

I have two of these - bought them for ~£150 each as new (sans drives) one is still my NAS/homeserver running with 8GB of ram even though the spec says 54GB max. I decided to keep that one and supplement it with a N100 based system from AliE. I experienced the same issues, but my demands are not up to 2.5GB/s or 10G/s yet.

I currently run a k3s cluster and ran into the same issue core-wise. my "fix" was to only power the other one up when I need the extra cores 2 is not enough.

Your article makes me rethink if the other should get this treatment, and keep the MB as spare for the actively running system. 

Thanks for sharing!

Yeah there were some good deals on these when they were new. Mine came with a 250Gb HDD and a 4GB ram stick which I replaced both.

I had also tried pinning loads to one core, but it didn't help much.

The original motherboard is still in the case as a spare, although I'd have to un-mod the PSU (rejoin two wires) to use it. Probably should've crimped on some connectors to make that easier 😆

This is such a cool project! I have one of these collecting dust, looks like a neat mod for a future weekend. Thanks for sharing this :)

Thanks! Theres something about these Microserver chassis which made me really not want to throw it away!