The HP ProLiant Microserver is a great little box for home use. It's advertised as low-power and quiet, you can put up to four hard disks in it as standard (with room for plenty more if you like modding) and with HP's cash-back deal you can get it for about £150 in the UK.
I use one as an always-on box running Logitech Media Server. For this I want it to be as quiet as possible, especially when it's not in use, so I've made a few modifications.
I need a reasonable amount of storage for my media, but most of the time this won't be in use. I've therefore got a separate SSD drive for the OS (Ubuntu Linux) and a 3.5" HDD for storage. This has loads of advantages:
Fitting an SSD to the microserver is easy. I've got mine in the space at the top as I don't have a CD-ROM. Even if I did, there's loads of space in the bit behind the lit HP logo (it's basically a floppy disk bay but with an LED stuck at the front). As SSDs are small and light, you don't really need to worry about securing them in the traditional way. Mine is currently held in place with blu-tack! If I need a more rugged fitting, I may change this to gaffa tape. :-) Only one potential gotcha really - don't forget a Molex to SATA power converter as there isn't a SATA power lead in the server.
But this isn't all that needs doing! You'll need to install a custom BIOS if you want the disk to work at full speed.
The Microserver's internal SATA port that I'm using for my SSD is designed for a CD- or DVD drive and so runs in IDE mode. This means it will not allow a fast disk plugged in to this port to work at full speed. The same applies to the external eSATA port. There's no way to change this using HP's BIOS, but you can by installing a custom BIOS.
I've used a modified bios provided by TheBay on avforums.com. This adds a new menu allowing you to disable IDE mode on these two ports (4 & 5). With this set to disabled, the ports run in AHCI mode, which is significantly faster. The other SATA ports already run in this mode - these are used by the drives in the HDD caddies.
You can get the modified BIOS from http://www.avforums.com/forums/networking-nas/1521657-hp-n36l-microserver-updated-ahci-bios-support.html and there's a useful post at http://www.avforums.com/forums/16332889-post114.html explaining how to flash this from Linux using flashrom. Windows user? - download the official HP bios and follow their instructions to create a bootable USB key. When finished, replace the .ROM file on the USB key with the custom .ROM file.
I used flashrom to install Microserver AHCI BIOS O41072911. Once installed, launch the BIOS menu on boot (F10) and go to Chipset -> SouthBridge Configuration -> SB SATA Configuration and set SATA PORTS 4/5 IDE to Disabled.
The main case fan is a bit noisy and can be swapped for something much quieter. Silent PC Review have an excellent article on how to do this. I've used the same Scythe SlipStream that they use. This also has a manual speed control, designed to be on the outside of the case. I've just put mine in the CD-ROM bay, next to the SSD. Held in place with more blu-tack. ;-)
Tip: when fitting the replacement fan, don't forget to take the metal cage off the stock HP fan and fit that onto the new fan. Otherwise, the HDD cables can easily end up touching the fan blades.
HP claim a maximum of 24dBA for the Microserver, which should be relatively quiet. However, mine is a lot louder than this and several others on the internet claim the same. A lot of this noise comes from the power supply fan. I've got the N40L version of the Microserver, which is an upgrade over the original. It's possible that HP switched the power supply to a noisier model with this version but have kept the low-noise claims from the original. Either way, even 24dBA would be too loud - I want this thing to sit in my dining room!
Mini-Box.com make a tiny, fanless power supply: the PicoPSU. This is a DC-DC power supply so has an external AC-DC adapter, like a laptop charger. I had a spare of the 120W version so have used this - 120W is fine for my needs, but probably wouldn't work if I was using four HDDs as the power-on spike as they all spun up would likely be too much. The PicoPSU fits into the Microserver's ATX connector beneath the drive bays with about 2mm to spare! With this installed along with the new fan, the server is silent!
In order to properly fit the PicoPSU, a little bit more tweaking is needed. The power cables that come with it will not reach the disks and the 12V input cable from the external AC-DC adapter won't reach the outside of the case. This is easily fixed using a few extension cables. To take the power from the PicoPSU to the disks, I used a 30cm Molex extension cable (Akasa AK-CBPW02-30). I then used a Molex splitter cable to connect this to my SSD and HDD - you'll need more splitters if you want to use more HDDs. For the SSD, I also needed a Molex to SATA power apapter cable.
To run the PicoPSU's 12V input cable to the outside of the case, I used a 30cm, 4 pin 12V ATX power extension cable. The existing cable on the PicoPSU simply unclips into two parts and you can then fit the extension cable in between. I drilled a hole in a spare PCI-E blanking plate and fitted the AC-DC barrel connector to this. This gives a very neat external finish whilst leaving the entire fit reversible if necessary. However, you can just as easily feed the cable through the Microserver's flip-down expansion cover on the back - the cables will be slightly messier, but they are out of site at the back of the server anyway.
All of these cables are available easily and cheaply on the internet.
I've not been running my Microserver like this for long, but will try and remember to update this page if anything goes wrong.
Your mileage may vary! I'm providing the details on this page for information only. Modifying devices from the manufacturer's original specification can be dangerous and may make things blow up/catch fire/create a hole in the space-time continuum and/or destroy your home/pets/loved ones. If in doubt, seek specialist advice.
Thanks are due to the people at Silent PC Review, AVForums and Overclockers Australia.