To clarify my usage, the largest part of what my rig does is serve media and files over the network and run uTorrent 24x7 (more up than down, FWIW), none of which are zero CPU tasks. Yes, a NAS will be even more frugal on power, and an AMD Sempron rig will have more available juice for any kind of crunching such as media conversions etc (though due to clever software the Atom 510 almost as quick as my Athlon 620 at some media tasks). You can also downclock the Sempron to save more power, and the cost will be pretty close to that of the Gigabyte boards you saw. However, there is still a real power saving, and I crunched the numbers - for 24x7 operation over a three year period with 30W power consumption difference - which is a very conservative estimate, the Atoms save close to 800 units. You can squeeze even more by opting to use a Pico-PSU, which will deliver a few watts of incremental savings. All of this adds up over time, unless of course you have equipment failure and then the counter resets.
It's all about what your needs and budget are at the end of the day. I saw the Asus and it's wasted on a dumb terminal (unless it isn't). Also it has 'only' 6 ports, which means not enough for me. Plus, after adding a CPU the cost is about 3x of what one of the Gigabytes will be, I had a similar setup a few years ago with one machine doing everything, running a AMD Phenom 9950 and with 5 hard disks inside for overnight downloading (at which time the CPU was downclocked to 800Mhz). It was foolish but it lasted till I finally got a gaming rig. Even then, I had a reasonably competent 24x7 machine that doubled as a surfing and daily use machine. Only after being hit with very high bills relentlessly did I realise the need to drop down to a proper low power setup. Believe it or not, the savings dropped me into a lower usage bracket and reduced my bills by about 400/- a month.
The Atom 510 and 525 are almost perfectly balanced between consumption, horsepower, footprint and TCO for tasks like this if you add a PCI SATA card. It may not be the best solution for everyone, but for me it is. I suspect given your needs, it might also be the best for you.
Now, to specifics -
the processor which is going to be main power consumer, will almost always remain in its lowest energy state when the NAS is idle.
Lowest energy state of a AMD Sempron 140 is higher than Atom D510 at medium power levels. You cannot compare these two platforms on power consumption. And as pointed out, the main power consumer is the drive, and the drive spins down. You don't need RAID 1 to maintain perfect data backup, disk shadowing software does the same thing for free and on disks such as WD Green which are not friendly to RAID boxes and OSes (the whole reason WD introduced the so-called Audio/Video drives)
I do not recommend atom boards with SATA expansion cards because:
1. Sometimes LAN chipsets are on PCIE bus, Thus less available bandwidth for both of them
2. NAS OS like freenas, Unraid, Nexenta are very picky about Hardware. Better keep the hardware as simple as possible. You might end up having driver issues.
1. As opposed to being on what bus? The PCIe bus is 5Gb/s per lane. A PCIe 1x connection serving a Gigabit an is using 20 percent of its available bandwidth. The Atom boards also do not have a PCIe slot, just PCI. Now let's add SATA 1 speeds on four ports (300Mb/s each), the IDE slot bandwidth (133Mb/s per device) and the PCI slot bandwidth (133Mb/s) and assume it's coming off of one lane. It still doesn't max out the lane. You might need to put the numbers down before committing statements of this kind.
2. Yes, and all of these are first tested on Intel hardware. Unless of course, you have personal experience of incompatibility with Atoms and NAS OS, which I'm eager to hear given that this is the kind of usage the Atom was designed for. In addition, most add-in cards have pretty solid Linux support because they've been part of storage subsystems forever - what do most servers run in terms of OS? In terms of storage controllers? If there is an area of concern it's with Home OSes such as Win7 and Win7 x64. Those are the OSes that are the worst in terms of driver support.
Why I recommend 8 GB RAM and Freenas
1. Freenas Recommends 1 GB RAM for every 1 TB of Data, and DDR3 RAM is cheap
2. Freenas runs on a pendrive ( no need to waste a whole harddisk for installation)
3. Freenas has ZFS
4. Its Free!!
I agree with point 4 wholeheartedly. It was my first choice too. However (and I had tried FreeNAS for a bit before going Windows) I was not willing to reformat 11TB of data drives with 8 TB of data on them and nowhere to keep it all temporarily. FreeNAS would not work unless I reformatted all of them to ZFS. Granted, it's a one-time process but it's more suitable for those who are literally going ground-up. The stupidly large memory footprint was simply not needed - 8GB RAM is cheap today but you're fooling yourself if you think your array is going to remain at the same size forever. When you upgrade your disks, you will have to add RAM if you don't want the NAS performance to drop. I ultimately found too many issues with FreeNAS so Windows 7 HB was used, and it is enough for this, really.
the HDD's run all the time. If you know which disks you need & if there is a mechanism to safely turn off particular disks then you can go for it
Just to confirm the WD Green drives spin down after about 5-10 minutes idle time and take about 5 seconds to initialise (this means everytime you access data after the drive has spun down, you wait for a good 6-7 seconds before your request is served, Of course, the drive is always available after that till the next idle cycle. In practice, it feels a lot better than it sounds. This is one of the reasons they don't work well in RAID arrays, they are optimised for quiet and low-power operation whereas RAID arrays demand high performance drives and offer instant availability of data.
