RAID Controllers a cautionary tale

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Rob James
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Joined: Jun 26 2001

I am not a novice at PCs but over the last few months I've often felt like one. If you are considering 'rolling your own' editing machine for HD then you need to be very careful when it comes to selection of motherboard and RAID controller.

First attempt:

An edit box based on an ASUS P5WDG2 WS Pro with Canopus SP and an Areca RAID card.

Result:

SP working fine. RAID card delivering blistering read performance (250MB/S from five 320GB Seagates in RAID 5) However, soon discovered that write performance was dismal. (7.7MB/S) After a month of tooing and froing with Areca technical support it seems this motherboard has both PCI-X sockets on the same bus segment and the Canopus hogs most of the write bandwidth. (Which figures I guess since it is writing HD to screen(s) etc.)

Second attempt:

Intel S5000VXN mobo again with the Areca. (No extra hardware this time, the box is intended for 3D graphics)
This combination won't even get past POST without hanging. No real idea why and web trawling has failed to give any clues. (As an aside, this is the least friendly mobo I've ever encountered, installing updates and various drivers has been an absolute nightmare)

Now, don't get me wrong, I like solving these problems and it is part of my job. If I wanted a reliable edit system with no hassle I'd be talking to DVC or similar.

The point is, if your time is money then don't even think about building a high-end system with hardware RAID unless you know exactly what you are doing. (And even then I'd be tempted by the back-up from the likes of DVC)

Rob The picture is only there to keep the sound in sync

Claire
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Joined: Apr 28 2001

Gosh, I must have been extremely lucky :eek:

Rob, a question, how did you measure the write performance while Canopus was doing it's stuff and "stealing" the resources?

Not that I have noticed any issues with my Asus P5W DH Deluxe, Edius NX and Raid 0 but I would be interested in knowing what is going on.

Claire

Rob James
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Joined: Jun 26 2001

Hi Claire,

I'm guessing you're using on-board RAID.

The bit of software that finally gave the game away was, from memory, a little utitily called 'PCI-Scope' I'll check in the morning and post again if it's anything else. If I'd just wanted RAID 0 I would have used the on-board controller (The Intel not the Marvel given some of the stuff I've read) But I wanted RAID 5.

Also worth noting that your mobo is significantly different from the P5WDG2 WS Pro.

As per my original post, you either have to be very lucky or very persistent if you're going to DIY a configuration that isn't already proven. The Intel board has been a complete nightmare. In the case of the ASUS it's just my bad luck/judgement that the PCI-X sockets are not on different PCI bus segments. (And the mobo manual implies that two 100Mhz PCI-X cards can happily co-exist... Well, they can if you don't mind one of them pinching most of the write bandwidth!))

Rob The picture is only there to keep the sound in sync

Nigel Longman
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Joined: Apr 28 1999
No problems here either (yet)

Rob

Sorry to hear of your woes regarding your RAID sets.

I can only echo Claire's comments that building my HD editing computer with an ASUS P5B Deluxe motherboard (similar to her P5W DH Deluxe) has been straightforward including the RAID implementation using the onboard ICH8R Intel southbridge chipset. I have previously posted some results of my experiences in a thread below yours for anyone that was interested, and they show how abysmal the RAID5 write speed was compared with RAID0.

My understanding is that the controller has to calculate and distribute parity bits among the drives to provide security against drive failure and it's this process that slows down the write speed. Maybe having 5 drives slows it down even more. Are you 100% sure that it's a bandwidth problem and not just RAID5 doing its thing?

Good luck, NL

Rob James
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Joined: Jun 26 2001

Nigel, thanks for that. The whole point of investing in the Areca RAID card is that it has a dedicated Intel engine to calculate the parity. Other folks are getting write speeds from this only slightly lower than a single disk. When I remove the Canopus card, so do I.
So, sadly, it really does look like a two slots on a single bus segment PCI-X bandwidth problem, at least as it is implemented on this specific mobo. I should add that I also tried out other permutations including two disk RAID 0 and the write speed remained resolutely at 7.7MB/S

Rob The picture is only there to keep the sound in sync