onboard raid vs expensive raid cards?

Maezr

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Jan 20, 2002
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what exactly is the difference? what warrants using one of the expensive cards?

I tend to use / need a lot of space, and I already have 2 500gb drives [and a lot of other drives, but I couldn't use those in the array] and I'm about to purchase more space so I figured raid was a logical jump. I'm figuring raid 5.

main questions:

1) onboard or raid card? why?

2) is the slowdown from using raid 5 for writes significant? should I use raid 5 just for a "data" array and have my main drive be something else?

3) anything else in particular I should be aware of?
 

Madwand1

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Jan 23, 2006
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Be specific. Which on-board controller? Which motherboard? Which inexpensive add-on card?

And how are you going to be accessing this array / what sort of data will you be accessing where performance will matter?
 

Maezr

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Jan 20, 2002
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I'm wondering in general. no specifics in mind. my motherboard is the P5B Deluxe though.

it's mostly for storage (movies, music, other data that's rarely accessed). but since I'm setting it up I'm wondering if I should have my primary drive seperate or within the array. the system itself is used for a lot, mostly a ton of multitasking.
 

Fullmetal Chocobo

Moderator<br>Distributed Computing
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May 13, 2003
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To be honest, I haven't messed with motherboard controllers at all. I have one hard drive connected to the mobo for boot, and that's it. For me, it's the options that a RAID card provides that make it worth it to me. I can take an array and transform, change, and expand it as I need to on the fly, and you can't do that with motherboard controllers. Plus the ability to take it from one machine to the next is unbeatable. And the performance of my RAID 5 and RAID 0 arrays are not bad at all, so I will keep with my methods. :)

EDIT: (after your recent post). I always have a drive for boot plugged into the mobo. It makes things much easier for setting up, and I'd rather have it external to the RAID arrays for ease of reformatting and the like.
 

Madwand1

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Jan 23, 2006
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Originally posted by: Maezr
I'm wondering in general. no specifics in mind.

You can't easily generalize this. Sure, tons do, but as there's no official RAID standard, and implementations can and do vary a lot, generalizations are often wrong and not nearly as useful as specific information.

Originally posted by: Maezr
my motherboard is the P5B Deluxe though.

That's useful information. It has an Intel ICH8R controller, which is quite good for on-board RAID 5. Sequential RAID 5 read/write performance can be quite good locally. You probably won't beat it with an inexpensive add-on controller. However, you can beat its feature set with a not-too-expensive add-on controller, e.g. Highpoint 23xx series. The Intel controller stops at 4 drives in a single array, and doesn't even directly allow expansion from 3-drive RAID 5 to 4-drive RAID 5. The Highpoints can do that and more, and give also give decent performance.


Originally posted by: Maezr
it's mostly for storage (movies, music, other data that's rarely accessed). but since I'm setting it up I'm wondering if I should have my primary drive seperate or within the array. the system itself is used for a lot, mostly a ton of multitasking.

In either case, until you get to much more expensive controllers (e.g. Areca/3ware), RAID 5 writing will cost you something in CPU utilization. How much? How much will it matter? These are hard to say. They both depend on what exactly you're doing. For some tasks, e.g. file serving, the CPU utilization isn't very important with decent modern CPUs. For others, it depends...

Small/random RAID 5 writes are also always slow. Only very expensive controllers with a lot of on-board RAM help here -- essentially by caching lots of small writes.

I strongly recommend keeping the OS on a separate drive from the storage array. Things sometimes get a lot simpler when you do it this way. You can also gain some performance advantage by being able to access the OS/swap/temp/personal folders concurrently with your data.
 

Fullmetal Chocobo

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Originally posted by: Old Hippie
games -- 2 x WD 150gb Raptor (RAID 0) on Areca ARC-1220 PCIe RAID controller)
Nice. :thumbsup:

Thanks. I'm looking forward to adding a drive on each of the RAID arrays. I can't wait to see what 3 150gb Raptors does in RAID 0. :) Should be interesting.
 

superHARD

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Jul 24, 2003
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As Madwand1 said, you will now want your OS on your raid...if something happens to the raid, you will be able to boot still, and rebuild your raid.

Freenas has softraid...I like it :)