Building own NAS

[Zeno]

Currently looking to build my own NAS device using (probably) an Intel
Atom ITX MB running some flavour of Linux.

I'm looking for a small case to take up to 5x3.5" drives but cant find
anything smaller than standard ATX cases.

Also as Atom boards don't come with RAID is there any cheap worthwhile
cards which will do RAID5. Initially the device is going to have
3x500GB drives in RAID5 but later 5x1TB(or bigger).

Cost is a factor (otherwise I'd buy a ready made device) and hopefully
could come in around £300 or less although it could be stretched a
little maybe.

Any suggestions?

 

[Al Dykes]

Currently looking to build my own NAS device using (probably) an Intel
Atom ITX MB running some flavour of Linux.

I'm looking for a small case to take up to 5x3.5" drives but cant find
anything smaller than standard ATX cases.

Also as Atom boards don't come with RAID is there any cheap worthwhile
cards which will do RAID5. Initially the device is going to have
3x500GB drives in RAID5 but later 5x1TB(or bigger).

Cost is a factor (otherwise I'd buy a ready made device) and hopefully
could come in around £300 or less although it could be stretched a
little maybe.

Any suggestions?

Several companies make racks that will fit 3 drives in two openings.
There may be a 5 drive version of this.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817990003

 

[Yousuf Khan]

Also as Atom boards don't come with RAID is there any cheap worthwhile
cards which will do RAID5. Initially the device is going to have
3x500GB drives in RAID5 but later 5x1TB(or bigger).

Cost is a factor (otherwise I'd buy a ready made device) and hopefully
could come in around £300 or less although it could be stretched a
little maybe.

Any suggestions?

Why bother with RAID cards? Just go with Linux's built-in software RAID.

RAID cards are nearly always software RAID themselves, except they use
use a proprietary RAID implementation specific only to them.

Yousuf Khan

 

[Arno]

Currently looking to build my own NAS device using (probably) an Intel
Atom ITX MB running some flavour of Linux.

I'm looking for a small case to take up to 5x3.5" drives but cant find
anything smaller than standard ATX cases.

Also as Atom boards don't come with RAID is there any cheap worthwhile
cards which will do RAID5. Initially the device is going to have
3x500GB drives in RAID5 but later 5x1TB(or bigger).

Use Linux Software RAID. Reliable and fast, and you don't have data
recovery issues if the controller dies.

And, no, there are no cheap RAID cards that actually do hardware
RAID, the cheap ones all do software RAID, but if a far lower
quality than what Linux already has.

Arno

 

[YKhan]

Use Linux Software RAID. Reliable and fast, and you don't have data
recovery issues if the controller dies.

And, no, there are no cheap RAID cards that actually do hardware
RAID, the cheap ones all do software RAID, but if a far lower
quality than what Linux already has.

Plus, an Intel Atom wouldn't cut it as a RAID controller anyways,
unless all one is doing is striping or mirroring. RAID5 requires more
power. Perhaps a cheap AMD Athlon ITX board would be more appropriate.

Yousuf Khan

 

[Arno]

Plus, an Intel Atom wouldn't cut it as a RAID controller anyways,
unless all one is doing is striping or mirroring. RAID5 requires more
power. Perhaps a cheap AMD Athlon ITX board would be more appropriate.

I am not so sure about that. It may even be fast enough for RAID6,
in any case if this is on a 100Mbps link. If it is GbE, it may
slow things down, but more likely because of other bottlenecks
than the CPU.

Incidentially, here is the power-on speed test from my
relatively slow Linux AMD Sempron(tm) LE-1250
Fileserver/Firewall/NAT system:

raid6: int32x1 1035 MB/s
raid6: int32x2 1011 MB/s
raid6: int32x4 851 MB/s
raid6: int32x8 621 MB/s
raid6: mmxx1 1773 MB/s
raid6: mmxx2 3277 MB/s
raid6: sse1x1 1757 MB/s
raid6: sse1x2 3074 MB/s
raid6: sse2x1 3093 MB/s
raid6: sse2x2 4074 MB/s
raid6: using algorithm sse2x2 (4074 MB/s)

Yes, that is about 4 Gigabytes/sec for RAID6. Other RAID
levels will be at least as fast as far as the CPU is concerned.

The thing here is that the mathematics in a RAID5 or RAID6 (with
ath most one disk missing) is very simple and can be done in
the SSE2 units. But even ordinary integer atrithmetric would
be more than fast enough.

After a bit of searching for a dmesg for an Intel Atom with
RAID6 found the following for an Atom 230 @ 1.60GHz:

[ 7.611051] raid6: int32x1 166 MB/s
[ 7.781052] raid6: int32x2 240 MB/s
[ 7.951052] raid6: int32x4 266 MB/s
[ 8.121052] raid6: int32x8 292 MB/s
[ 8.291052] raid6: mmxx1 357 MB/s
[ 8.461052] raid6: mmxx2 706 MB/s
[ 8.631052] raid6: sse1x1 292 MB/s
[ 8.801052] raid6: sse1x2 535 MB/s
[ 8.971052] raid6: sse2x1 586 MB/s
[ 9.141052] raid6: sse2x2 1076 MB/s
[ 9.142303] raid6: using algorithm sse2x2 (1076 MB/s)

(Source: http://bugs.gentoo.org/attachment.cgi?id=161290).

So, yes, the Atom is really slow, but still able to
more than saturate a Gigabit link with RAID6 as far
as the CPU is concerned.

Mind that there will be other bottlenecks and you will more
likely see something like 20-50MB/s (200-500Mb/s) with
such a simple set-up. Fas enough for almost anything
that crops up at home or in a small office.

Arno

 

[YKhan]

So, yes, the Atom is really slow, but still able to
more than saturate a Gigabit link with RAID6 as far
as the CPU is concerned.

Mind that there will be other bottlenecks and you will more
likely see something like 20-50MB/s (200-500Mb/s) with
such a simple set-up. Fas enough for almost anything
that crops up at home or in a small office.

Well, it looks like some commercial interests agree with you about
using Atom inside a NAS. Mind you, it is only a 2-bay NAS box.

HEXUS.net - News :: QNAP launches Intel Atom-powered two-bay TS-239
Pro NAS : Page - 1/1
http://www.hexus.net/content/item.php?item=18287

Yousuf Khan

 

[Arno]

Well, it looks like some commercial interests agree with you about
using Atom inside a NAS. Mind you, it is only a 2-bay NAS box.

HEXUS.net - News :: QNAP launches Intel Atom-powered two-bay TS-239
Pro NAS : Page - 1/1
http://www.hexus.net/content/item.php?item=18287

Interssting. And with encryption, they basically have no choice.
The typically used ARM CPUs are too slow for that.

Arno