Mini ITX - Raid build, AT3IONT-I & Lian Li PC-Q08

[Tifosi]

After a recent thread here debating what to do with my 5 year old desktop which is a little overkill for my needs these days, I was looking to split out my desktop rig into a NAS / Server and a stripped down lean desktop.

My aim was to build a small, low powered, quiet box to act as a NAS with RAID but also with the ability to act as a media centre. After mulling over the various ITX board I decided to opt for the atom chipset due to power consumption with ION graphics to support hd video decoding. In the end I settled on the following:

Lian Li PC-Q08 - nice case with a couple of niggles 1) the case relies on the side panels for rigidity and thus has 6 small screws to keep the side on. It's a shame since it means it requires a screw driver whereas the rest of the case can be used without a screw driver. 2) The screws were quite torqued up out of the box which was a bit of a peeve as I very nearly stripped the heads off of 3 of the screws. Overall well built no motherboard screws included, come back to this later...

Asus AT3IONT-I Deluxe - my first ITX after years of shuttles! This has external laptop-esque PSU brick which is fanless which I'm tempted to velcro to the inside of the case since I am not using a traditional PSU. I have a concern as to whether the PSU will cope with 4 SATA drives but my math reckons it should be fine. Also no motherboard screws included!!

2x 2GB G Skill low voltage ram - not cheap or easy to find (thanks to Hexites for direction to this RAM) but will hopefully support my aim for a low powered box.

3x 1.5tb Samsung Ecogreen F2 - hopefully pretty low powered ~3.8w idle according to Tom's Hardware.

Samsung Blu-Ray SH-B083-L

FakeRaid vs SoftRaid
I opted for SoftRaid after reading of concerns regarding the use of a FakeRaid controller due to 1) driver availability for FakeRaid and 2) portability of the RAID relying on using the same type of FakeRaid controller again; which could be an issue if the motherboard failed in a couple of years and no compatible FakeRaid controller is available. This pointed me to Linux and I was keen to dabble with Ubuntu further.

Limitations
Due to the ASUS ITX motherboad only having 4 SATA ports and wanting to opt for RAID5, I'd need at least 3 of the SATA ports for the RAID and the remaining port for an optical drive (in order to allow function as a media centre / bluray player). This left the challenge of where to stick the OS. My initial thought was to use a USB stick with a persistent Live Linux OS, but after having hit and miss experience of persistance within Linux in the past (unsuccessful clean dismounts and lots of filesystem checking) I decided to avoid this option especially as it would protrude outside of the case. I also didn't want to install the OS onto the RAID since it was to be used solely for data and not OS.

Partitioning
After some further reading it appeared that the best approach was to set up the RAID and leave a small partition on each of the hard drives for the OS. The ideal approached seemed to be to mirror each of these OS partitions in RAID1 for redundancy in case one of the RAID disks failed. Due to my inexperience of Linux I decided not to mirror the OS partition since it was highly likely that I'd screw up the OS at some point and thus I really didn't want to mirror my mistakes. At a later date I'll look to RAID of the OS partitions.

Swap space
It also became apparent that there was an advantage of splitting the swap space over several drives for I/O, after a lot of reading I found that the kernel does not require the swap space to be on a RAID since the kernel can optimally manage the performance of swap file on several separate drives without RAID. However, should one of the drives fail and the swap space on the failed driveis in use, then the system would most likely crash, so there is a benefit to putting the swap file on to RAID for stability. At this point I ignored the last sentence perhaps to my peril, since I don't expect to be needing swap space given the 4gig of ram and I'm not sure if the system would be any more stable with swap on RAID1 - time will tell.

Final partition layout...

----------------------------------------------------------------------------
| Drive 1 | Drive 2 | Drive 3
----------------------------------------------------------------------------
1x 3tb | RAID 5 ext4
----------------------------------------------------------------------------
3x 20gb | /ROOT ext4 | /ROOT ext4 | Image of Drive 1 /ROOT ext4
----------------------------------------------------------------------------
3x 2gb | /SWAP swap | /SWAP swap | SWAP swap
----------------------------------------------------------------------------
3x 100mb | /BOOT ext2 | /BOOT ext2 | Image of Drive 1 /BOOT ext2
----------------------------------------------------------------------------

I opted to install the OS twice once to Drive 1 and a second copy to Drive 2, although not mirrored, this would give me a backup OS to get to the RAID array in case of Drive 1 failure. Eventually I'd like to mirror Drive 1 and Drive 2 but I'll wait until my Linux skills have improved first.

Drive 3 I left formatted to allow storage of cloned images of Drive 1 /BOOT and /ROOT, fully configured with all servers, settings etc. This is to allow restoration to Drive 1 or Drive 2 should I screw up the configuration beyond belief at a later date. I also backed up the /root and /boot images to an external hard drive.

All the drives were partitioned identically to allow easy cloning and backup. I'm not sure if there is an advantage to separating /boot and /root, this seems to be a common thing to do but I'm not sure why if anyone with Linux experience can shed light that'd be interesting?

Power Consumption

Using a home power meter the box is using:

ilde 38w at idle sitting at the desktop
peak 70w during boot with the optical drive running and everything spun up
normal load tbc

Further walkthrough to follow...