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RAID in WHS 2011


fblittle
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Does each SFF-8087 mini-SAS support four SATA drives? Is this always true, regardless of manufacturer?

 

Expensive, but the card below looks very nice.

 

areca ARC-1222 PCIe x8 SATA / SAS, $469

 

If THE CARD supports multilane SAS then yes all the 8087 will support breakout sata cables. Usually its a safe bet that 8087 means multilane support, otherwsie they would use the cheaper SAS/SATA connector.

 

That card is overkill for anything a home user would need.

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I would say that any RAID controller that doesn't have its own processor for the parity calculations isn't a true hardware raid card. This can become especially true when doing something more intensive like RAID5 or RAID6. Sure the CPU can handle it in most cases, but it will always be faster for the processing to be done locally.

What else is new?

 

What would classify it as then? Its an hba with a HARDWARE controller on it. Last time I checked that qualifies as hardware. On board parity processing is just an additional feature. The manufacturers agree, might want to let them know they gave classified their products incorrectly.

I'm trying to keep this simple so everyone who isn't a technician can understand how this all works. So that we all build from a correct and common point.

I understand no-control's point about trying to keep it simple. That's always a laudible goal. I also understand usacomp2k3's argument about hardware RAID. It is, in fact, the definition I have used to distinguish hardware RAID from other types since controllers first started appearing on motherboards.

 

The problem with defining hardware RAID by whether it is an add-in card or not is that most of the low-end add-in cards are simply a PCB with the same controllers on them as are on the motherboards. In fact, that's how they got onto motherboards - they started out as add-in cards and then moved to the motherboards, just like video cards did. If they're the same controllers, how can one be called firmware and the other hardware - they're both just chips. Perhaps one way to define both the mobo controllers and the low-end add-in cards is to call them firmware.

 

But, as per no-control's argument, this makes it more complicated to differentiate what is hardware RAID from what's firmware It gets to be a mess.

 

I don't go along with the manufacturers' claims as to what is hardware RAID because it's marketing hype. Of course they're going to say it's hardware; anything to make you think you're getting more than you are. Hey, that's business.

 

I finally settled on this definition for myself:

Software RAID is just that, software and nothing else; there can be no controllers of any kind, either add-in or mobo based.

Firmware RAID is any add-in or mobo based controller that depends on the main CPU for some of the RAID control. As has been mentioned numberous times, that often is the XOR functions, but it can be other things as well.

Hardware RAID handles the RAID aspect of the drive control entirely by itself. This requires the RAID controller, normally an add-in card, to have its own processor. It often has its own memory as well. The only thing the main CPU does is make calls to the RAID driver which takes it from there.

 

I don't believe there is any hard and fast way to define these things, but I've found my own definition useful when deciding how I'm going to set up a RAID system. YMMV.

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That card is overkill for anything a home user would need.

 

Agreed, but I couldn't find anything else that would classify as hardware raid and would support 8 drives. Unfortunately, I can't find the RocketRaid card that pcdoc bought.

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Agreed, but I couldn't find anything else that would classify as hardware raid and would support 8 drives. Unfortunately, I can't find the RocketRaid card that pcdoc bought.

 

 

Any RAID card is a Hardware RAID card. How would you use a software RAID card? Plug the DVD into a slot? HBA = Hardware in OS = Software

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Any RAID card is a Hardware RAID card. How would you use a software RAID card? Plug the DVD into a slot? HBA = Hardware in OS = Software

 

 

Okay, valid point. I want a card that does all the processing on it, instead of the MB.

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Okay, valid point. I want a card that does all the processing on it, instead of the MB.

3

 

Question in regards to Raid.

 

I planon using Raid (first time) on a new WHS 2011 build:

- OS will be on a Icy Dock with 2 WD Black laptop drives...from what I understand this is straigh forward

- Videos will be on a Highpoint RocketRaid 2680 card which is hardware based

- Photos / Data / Music etc will be on a 2TB drive which I plan on using Raid 1 from the motherboard (Gigabyte GA-H55M-UBS3)...is there any downside to this?

 

This is my first shot at Raid and I want to ensure I don't screw it up...any suggestions?

Tim

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  • 1 month later...

Any RAID card is a Hardware RAID card. How would you use a software RAID card? Plug the DVD into a slot? HBA = Hardware in OS = Software

 

I'm kind of resurrecting a dead topic here, but I think what I need to say might be useful to some people and I really don't know why I didn't say it before (my bad).

 

In a nutshell, there is a pretty big difference between hardware and firmware RAID 5 in a very specific operational situation, which is the dreaded RAID 5 rebuild. Please note the difference below.

 

Hardware:

1. Read data from all surviving drives

2. Compute original data from parity using hardware XOR chip

3. Write original data back to spare drive

 

Firmware:

1. Read data from all surviving drives

2. Send all data up the drive interconnect to the CPU, compute XOR, send computed data back down to controller

3. Write original data back to spare drive

 

As you can see, in the case of hardware rebuild, the drive bus doesn't get flooded with rebuild traffic. This is not a big deal with modern systems where drives have dedicated SATA channels and the CPU can take the punishment. However, things are very different when using IDE, or the infamous (cheap) PCI soft RAID cards. In those cases, the rebuild traffic easily overwhelms the bus, with two potentially nasty effects. Firstly, the drive rebuild gets bottlenecked and the array spends more time degraded, exposing it to secondary failure for an extended duration. Secondly, there is a quite noticeable performance hit during the rebuild which usually renders the system unusable.

 

This is why I recommended some thought on this when recycling parts. It's tempting to throw in an old PCI Promise card, and then try to run RAID 5 on it, but you just could be setting yourself up for some pain later...

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