Pros: 4x SAS ports and 4x Gig network ports in this small form factor is really awesome.

Cons: Had to make driver modification to get SAS controllers to be recognized

Other Thoughts: I have 2 of these motherboards running Ubuntu 15.10 with ZFS as the file system and I couldn't be happier with them. Follow these guides to recompile the SAS driver.
permalink . gmane . org/gmane.linux.scsi/99330
askubuntu . com/questions/515407/how-recipe-to-build-only-one-kernel-module

Pros: Been running for one year on Ubuntu server without any issues.
Recently switched to UnRAID where it seems to be working well for the first two weeks so far.
Tons of connections for drives

Cons: Only two USB ports, no motherboard headers, and no 3.0 ports is the only detractor for me so far

Pros: 4 Network interfaces + dedicated management interface
16 drive SATA/SAS controller built in
M.2 port for storage
x4 PCIe expansion slot
6 fan headers and 1 temp probe header

Amazing Mini ITX motherboard that would be perfect for any DIY NAS

Cons: SAS/SATA controller is COMPLETELY USELESS and does not work with anything
2 USB ports total, no internal headers to add more (This is a joke right?)
2 SATA ports or 1 SATA port if you use the M.2 port
Strange booting issues, disks seem to come and go as they please. Expect to hard reset this motherboard often.

Other Thoughts: I don't understand how this motherboard is a huge failure. I mean it's dangold near perfect for what it could be used for and that is a DIY NAS or really any type of storage box. 4 network interfaces and a 16 drive SAS controller that works with SAS expanders just fine. Please note this is not a RAID controller just a standard HBA for SATA and SAS disks. I mean perfect right?

The one issue with this board and the biggest one is that is does not work with anything. The onboard SAS controller is some type of garbage Marvell chipset and again works with NOTHING YOU CAN USE.

FreeNAS=NOPE, OpenMediaVault=NOPE, XPEnology=NOPE, NAS4Free=NOPE, uNRAID=NOPE, Openfiler=NOPE.

Nothing works with the onboard SAS controller. The person who wrote the review that is works with OMV is lying because so far it does not work with it. It's really a shame this is a great piece of hardware for the price and the other flaws could be over looked like the 2 USB and 2 SATA port choices if only THE ONBOARD SAS/SATA controller worked.

Waste of money I wish I listened to the whole "if it's too good to be true...." you know the rest. Buy a different Mini-ITX motherboard and a LSI controller and be happy that it works with everything unlike this hunkojunk.

Last thing, nowhere does it state the Marvell controller is a NON RAID CONTROLLER and is only a disk HBA. No wonder why NewEgg tossed in a free PCIe USB3 HBA with this motherboard.

Manufacturer Response:

Dear Valued ASUS Customer,

Thank you for taking the time to write this review. We appreciate your feedback on this matter and I will be letting the related department know about the issues you are experiencing for future improvements to this product. What is the DRAM part number you have in your system? Have you updated your SATA drivers to Version 4.0.02020? Which Operating System are having issues with? What BIOS revisions are you currently operating on? Please provide with a detailed description of your issues so I can better assist. If you need further assistance with any technical questions or inquiries feel free to email me at cl-nestor@asus.com. Please don’t hesitate to contact me using this reference number N151286183.

Thank you for choosing ASUS!

Best Regards,
-Nestor
ASUS Customer Loyalty – US Support
https://www.asus.com/us/support/callus

Pros: Lots of features for the price.

Cons: Cannot get Linux to recognize the SAS controller. ASUS offers drives for older versions of Centos, but nothing for the Centos 7 and nothing for Ubuntu. Neither version of Linux will recognize the SAS controller. ASUS tech support said we're on our own with Ubuntu. Ran a demo of Windows 2012 R2 with some success, but that's an investment we're not willing to make. Don't buy this board for use with Linux.

Manufacturer Response:

Dear Valued ASUS Customer,

Thank you for taking the time to inform us on your experience with the P9A-I/C2550/SAS/4L. We appreciate your feedback on this matter and I will be letting the related department know about the issues you are experiencing for future improvements to this product. What kind of troubleshooting have you tried so far? Have updated to the most recent BIOS version? If you need further assistance with any technical questions or inquiries feel free to email me at cl-nestor@asus.com. Please use N151285969 ​in your e-mail header as reference to this case.

Thank you for choosing ASUS!

Best Regards,
-Nestor
ASUS Customer Loyalty – US Support

Pros: Can't beat this board for dollars per SATA/SAS port. 16 SATA 3Gbps ports, motherboard with ECC support, built-in BMC and works in Linux? noice!

Cons: DOA.

Additionally, the board doesn't ship with a paper manual of any kind. So you'd best have an optical drive somewhere to pull off the PDF.

The manual itself isn't up to normal ASUS quality. It lacks any coverage of what the power indicator lights mean. It's also a flimsy IO shield with the little knife-like grounding shield tabs.

It also didn't come with too many breakout connectors for all of the LED connectors it supports.

Other Thoughts: Newegg of course RMA'd the board without issue, but I had to completely revamp my plans because this board wasn't working. It wasn't able to be replaced, it was simply refunded. So that meant a whole different setup the next time around. I hope I don't get charged a restock fee for returning the other components that I bought to go with it.

Manufacturer Response:

Dear Valued Customer,

I am sorry to hear that your board was DOA and the inconvenience that it caused you, since you have to return parts now. I hope everything works out. If you have any questions or concerns, feel free to contact me at cl-justin@asus.com and I will help you to the best of my abilities. Your case # for reference is N150966506

Thanks for choosing ASUS

Regards,
Justin
ASUS Customer Loyalty

Pros: On paper it's outstanding

Cons: Biggest headache ever.
To date:

1. Cannot boot from a USB stick. Can't. No matter what choices I make in the bios.

2. Cannot install 2012 R2 using ISO from Microsoft via DVD install. Get prompted for drivers which neither provided disk nor downloaded from website resolve.

3. Cannot install Win 7 64 Ultimate using ISO from Microsoft via DVD install. Get prompted for drivers which neither provided disk nor downloaded from website resolve.

4. Can install Ubuntu server.

5. Can install 2012 R2 Essentials using ISO from Microsoft via DVD install. However, unstable and OS hangs repeatedly.

6. Cannot upgrade BIOS. Try to run program BUpdater but told wrong OS. Did download the listed installer for 2012 R2.

7. Cannot install FreeNAS. Hangs at Booting "FreeNAS Installer". Turns out it's an unsupported OS.

Other Thoughts: I have been a loyal ASUS user for their consumer line. This was my first Server purchase. Never doing it again.

Manufacturer Response:

Greetings Aaron,

I am sorry that you are having issues with the motherboard sir. Had you tried more than one USB flash drive on the board? What drivers were being requested? At your earliest convenience, please contact me through email, including your reference number within the subject line, and we can discuss this case further. In addition, please provide me with what troubleshooting steps you have tried, as well as the rest of the systems hardware configuration. Thank you. Cs#N150220086

Regards,

Lou
ASUS Customer Loyalty
cc-lou@asus.com

Pros: I recently needed to upgrade my NAS (Netgear ReadyNAS NV+) as I was reaching capacity. I wanted a box that was easily expandable and relatively affordable. Unfortunately, most pre-built solutions are expensive and either do not allow external modules or the modules cost almost as much as a new standalone NAS.

Due to the reasons stated above, I decided to make a custom solution instead. This board has been working great since I installed it. I am running a RAID 6 fully populated with 8 2TB HDD with the two onboard mini SAS connectors. I've connected the remaining two mini SAS connectors to a SFF 8087-8088 adapter allowing connection to a external RAID enclosure in the future.

The processor is perfect for a NAS solution. Although I would have preferred the C2750 processor. At the time of purchase, it was not yet available. The C2550 processor has yet to be max out in terms of performance and has handled all the rebuilding and syncing I have thrown at it with ease. I've only peaked the performance at about ~60% load.

Overall, it's a nice mini-ITX board with great potential. If you're looking for a simple board to power a NAS, this is something I would recommend.

Cons: Unfortunately this board does not support FreeBSD. If you're looking at this board to run FreeNAS or similar, you might want to take a look at something else as the Marvell drivers are not supported on FreeNAS.

Pros: Works with ipfire and pfsense.

Cons: Unfortunately, generates a lot of heat powering the SAS controllers. There is no way to disable the controllers. FreeNAS would install but not recognize the SAS controllers. Not much use without those.

Other Thoughts: OK board to use as a firewall, the NICs are recognized by ipfire and pfsense. You won't be able to go fanless because of the heat.

Manufacturer Response:

Dear Valued Customer,

I do apologize but unfortunately the Marvell SAS controller does not support FreeNAS. If you would like to discuss this case further, please contact me through email, including your reference number within the subject line. Thank you. Cs#N140930234

Regards,

Lou
ASUS Customer Loyalty
cc-lou@asus.com

Pros: Seems like a quality board.

Cons: Does not boot FreeNAS/NAS4Free. Driver incompatibility with the NIC and SAS cards.

Other Thoughts: This was an ideal board for my needs but does not have drivers available for BSD 9 based OS's.

Manufacturer Response:

Greetings Alundy,

I do apologize that you had issues with the board. You are correct, unfortunately the Marvell SAS controller does not support FreeNAS at the current time. if you would like to discuss this case further, please contact me through email, including your reference number within the subject line. Thank you. Cs#N140930149

Regards,

Lou
ASUS Customer Loyalty
cc-lou@asus.com