[XCSSA] Recommendations for a SAMBA/NAS device?

[X-otic Computer Systems of San Antonio]

Actually Tweeks, I disagree with you :)

Drives consume what like 15W per drive (I'll have to look it up but I  
don't have much time as I'm in a break from training). You do not need  
a RAID card to spin the drives down, either. 'hdparm' should be able  
to take care of that, even on SATA drives. Now, it is true that  
writing to the array after one or more drives is asleep could cause  
Linux to hang. In that context, a hardware RAID controller might still  
be a better choice.

As for the CPU, modern procs chew up 100W of power. Even the low power  
modern chips hum away at 65W. So, it indeed makes sense to use a lower  
power CPU that draws 5-10W assuming that CPU is powerful enough for  
your application (which a NAS qualifies). Those chips also throw off  
far less heat (some can be totally cooled passively) which,  
indirectly, impacts your cooling bills.

In a NAS, your bottleneck is likely going to be network or disk I/O.  
That gives the CPU more time to do stuff such as mess with LVM and  
Software RAID. Even a low-power chip is more than enough in most  
cases. That's why so many off-the-shelf units use ARM. Good enough  
performance but AWESOME power consumption.

Now, the hidden issue is the power supply. That thing could still be  
inefficient in the grand scheme of things. But, some ITX boards allow  
for a simple +VDC power input, meaning you could power it with a  
sufficiently large power brick. Some ITX cases (some specifically  
designed for NAS) also have a low power supply, somewhat akin to  
laptops (though built for that purpose). They aren't exactly cheap.  
But they work.

Similarly, software RAID is probably all you need. As long as the SATA  
controller supports hot-plug then Linux can handle the rest (if hot- 
plug is even an issue). In other words, you can still remove and add  
drives without reboot. And the performance of a RAID controller could  
be negated by the network medium. Not to mention you have to pay $$$  
for a PCI-Express or PCI-X controller card to see all of the benefit,  
because otherwise you are at the mercy of the PCI bus. By today's  
standards, that's not very fast at least when pulling data from the  
RAID controller's on-board cache.

I should point out that I haven't hooked up a smart surge protector to  
meter this or anything :) But I have seen people do these sorts of  
tests for modern motherboards, and the motherboard/CPU does indeed eat  
up a lot more power than you might otherwise think.

$0.02

Tim S.

On May 21, 2009, at 10:55 AM, X-otic Computer Systems of San Antonio  
wrote:

> On Wednesday 20 May 2009, X-otic Computer Systems of San Antonio  
> wrote:
>> Hello everyone.
>>
>> I'm trying to solve a major power issue at the house and am hoping
>> that someone can shed some of their energy managment insight.
>> [...]
>> The problem is
>> that four of those drives are SATA 750GB drives and are hanging off  
>> of
> [...]
>> My thinking is that a low-powered machine, like an embedded system
>> would do it nicely,
> [...]
>> What do you guys recommend? What are your experiences with home-NAS
>> solutions?  What issues did you encounter and what did you do to fix
>> them?
>
> I think that your thinking is off.. Using a low power embedded  
> motherboard is
> barely going to touch your power consumption when 85% of your NAS  
> power is
> being consumed by the spinning drives (not the motherboard).
>
> I don't mean to sound harsh.. but what you need to do is to look in  
> to using
> a "real RAID card" with battery backed up cache, write back cache,  
> and power
> control so that when he array is not being written to.. the drives  
> can be
> spun down.  Then when a write happens.. it writes to the cache and  
> goes on
> while the RAID card wakes up the drives and spins them up.  Some  
> reads can
> even stay cached.
>
> Some OTS home-NAS systems do this now.  But nicer RAID cards that  
> can handle
> this type of stuff are the nicer LSI, Adaptec and 3Ware IIRC SATA  
> and SAS
> cards.
>
> There are a couple of folks on list who have built such systems...
>
> Tweeks
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