Low-Power RAID5 Fileserver

[rcllbrg]

I'm looking to build the lowest-power possible fileserver to keep always-on and serve files to my LAN, do multifunction internet things like download slow torrents for months on end, and also act as a PVR if possible, so onboard TVout and MPEG2 acceleration would be a plus.

I was looking at some prebuilt Intel XScale-based NAS enclosures like Infrant's ReadyNAS NV but I decided against them as they only offer some basic FTP function with the networked storage. If the price is a thousand dollars for a NAS-only box I may as well build a SFF box that can do more things than just networked storage.

Due to their ultra low power consumption(19W max on EK series) and built in MPEG2 decoding acceleration, I'm looking at the newer VIA Mini-ITX boards- EPIA-EN15000G: 1.5GHz C7, 1xDDR2-533, GbitE, HDTV TVout or EPIA-EK10000G: 1GHz 'Luke CoreFusion', 1xDDR1-400 with a PCI riser and additional cards. The main problem I see with these VIA boards is that they have no onboard RAID and they only offer one PCI slot, not PCI-X or PCI-E. For a multiport RAID5 card I think the standard PCI bus on these EPIAs will be a major I/O bottleneck.

I plan to run 4 to 8 7200RPM drives on a RAID card. As I understand it, 7200RPM drives can't physically spin fast enough to even saturate PATA-133 let alone SATA-150 or SATAII-300. I've seen benchmarks for 7200RPM drives hover around 70MB/s max burst rate down to 30MB/s, so lets say an avg of 50MB/s per accessing drive. 2 or 3 7200RPM drives transferring at once will probably not bottleneck the standard PCI bus. 5 or 6 7200RPM drives transferring at once will definitely bottleneck the PCI bus. VIA's page is also unclear what revision of PCI they are using for their 1 PCI slot.

I noticed there is a newly announced Mini-ITX board with a PCI-E x16 slot, not for purchase yet. Runs Pentium M 760 2.0GHz(27W) or Celeron M 370 1.5GHz(?W), 2xDDR2-533 DIMM/2GB max, 2xGbitE on the PCI-E bus, but it has very basic features on its Intel GMA 900 integrated graphics. The ability to use a PCI-E RAID card solves any I/O bottlenecks for sure, but that option kills the ability for a PCI-E video card with adequate PVR features -since the integrated Intel graphics are lacking. I suppose the functions of a RAID fileserver and a PVR shouldn't be mixed, but it would be nice to do both in the same box.

I was wondering if anyone recommends a Pentium M based SFF board that has either onboard RAID or PCI-X/PCI-E for a RAID card, onboard GbitE would be nice. PVR VI/VO stuff like onboard hardware MPEG2 encoding(heh), MPEG2 accelerated decoding, HDTV TVout would be a plus. I'm also curious about the power consumption of the Pentium M versus the VIA C7 or the 19W 'Luke CoreFusion' in the new EPIAs.

 

[gaidin123]

Heya,

You've got a number of options to build a home NAS with RAID5. If you are going to build a storage box I'd recommend dedicating that box to doing storage. You aren't going to like listening to 4-8 drives spinning in any enclosure while you're trying to watch a movie with it in the same room.

No hard drive right now can saturate the standard bus its on in any sort of sustained manner. If you are planning on using RAID5 remember that data is both written to and read in a round robin manner. All the drives are not transmitting/receiving at the exact same moment so some of your bus limitations are lifted though old PCI is going to be saturated. Writes are especially hard on RAID5s due to parity calculations which is where a hardware card comes in to play. However for many applications software raid in linux/bsd is more than adequate.

3ware/AMCC's PCI-X sata raid cards also fit in standard PCI slots and should be getting pretty affordable now with PCIe taking over. Don't forget if you're using a PCI based system your NIC is probably also hanging off the same PCI bus fighting for bandwidth when you want to transfer something over the network to/from it. Also your onboard sound, onboard IDE drives, etc. may also be on that same shared PCI bus. PCIe has helped this problem a lot by generally sticking the NIC on its own PCIe x1 bus and of course each pcie lane is mostly dedicated bandwidth.

The Via miniitx boards are certainly low power compared to standard PCs. You will still need a good power supply to handle spinning up a bunch of drives at POST. If you go with something like an amd64 box you can use the cool n'quiet driver to downclock while idle.

The main thing miniitx has going for it is the integration and all in one nature of the form factor along with relatively low power consumption. You're going to need a midtower case to hold up to 8 HDs without getting overly creative/modding. Since you're already going to need a standard PSU and standard case I'd recommend going with an onboard video matx board and something like an amd64 due to the low cost (core 2 duo if you want but you don't need it for storage).

Hardware RAID cards aren't cheap in general. I definitely like the 3ware cards. For home use honestly something like FreeNAS or linux + standard software raid when paired with even the slowest amd64 chip should give you more than enough bandwidth.

The pentium m miniitx boards are generally pretty expensive. I think the cost savings in building a normal matx system paying attention to minimizing power consumption (ie onboard video, dynamic clocking for power saving, fan control, 80%+ efficient PSU) will give you a better overall system that uses marginally more power than a pentium m itx equivalent. You will be able to use PCI or PCIe and have all disk IO on PCIe and have a gigE NIC on its own PCIe lane as well.

Sorry if this is rambling but I've gone down this exact line of thinking several times and I always end up going with a standard system with well thought out components. My first system used a PCI 3ware raid card and now I'm just using software raid on linux and so far so good.

Gaidin

EDIT: Except for some server/workstation motherboards almost all "onboard RAID" cards require OS level drivers to do the actual RAID part. While they may be optimized some it is just an abstracted form of software RAID that will use your system resources for things like parity calculations. Examples of real sata/ide hardware RAID cards are the 3ware/AMCC line and the Areca cards. Generally all Highpoint and some Promise ones are just software RAID.

EDIT2: If you grab an SLI motherboard or one with a pcie x16 and x4 you may be able to stuff a high end video card and a real RAID card into the same box. We all know PCIe is supposed to be a general IO standard but I have had problems putting non video cards in x16 slots (ie a crappy Promise x4 PCIe raid card). I was never able to nail down whether to blame promise or the mobo manufacturer. Check out the storagereview.com forums for info on this kind of thing.

 

[piasabird]

In my opinion these Via Epia Motherboards are junk. Buy them at your own risk.

All the connectors are really jammed close together, and some connections are smaller than normal.

Compare performance on a benchmark.

 

[cheesehead]

Originally posted by: piasabird
In my opinion these Via Epia Motherboards are junk. Buy them at your own risk.

All the connectors are really jammed close together, and some connections are smaller than normal.

Compare performance on a benchmark.

The Epia boards, from what I have heard, work fine. You don't need much power for, say, streaming video anyway, and although they do have a history of funny quirks, I've heard few people really mad at them. The latest C7 boards are supposed to be great performers (equivalent to a similarly-clocked Dothan), but have a nasty sound output problem which should be fixed soon.

However, I would suggest getting an old AMD Athlon MP server board, and run it with one or none AMD "Geode" CPU's. The Geode 1750, IIRC, is just a super-low-power Athlon, and an inexpensive server board would give you PCI-X galore.

Alternately, try finding an old PIII server board. Most of the Celerons put out little heat; an under-volted 933mhz Celeron underclocked to 800mhz would likely work fine with passive cooling.


EDIT:

The PCI-16x slots are for video cards only.