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Onboard RAID vs Controller???

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December 11, 2006 3:37:12 AM

I hear onboard RAID is not as effective as aftermarket PCI controllers.. Any experience on this???
December 11, 2006 8:00:43 AM

Quote:
I hear onboard RAID is not as effective as aftermarket PCI controllers.. Any experience on this???


yes i do have experience on this, and the short answer is no, there is no real difference. there might exist, in some parts of the world, crappy no name north bridges, that support raid, but really just have software raid, but as long as its an Intel or an Nforce chipset, its a hardware level raid, and it will perform as well as an ad in card, if not faster in some instances because of hte lower latency from the north bridge, compared to an ad in card that has to go through the PCI/PCix/PCie bus then the northbridge, then to the processor.
altho realistically, you would need a RAM drive to test that, because hard drives are far to slow to push the bandwidth.
December 11, 2006 9:43:28 AM

Define effective. While you're at it, define the budget or which cards you'd buy and which board you have and what drives you'd want to use, and what the use is, needed performance level vs cost to get their (which is more important and how much more important).

I try to avoid running RAID off mobo controllers, mobos are more likely to die than add-on cards and I may switch drives to a different board that doesn't have same RAID controller built in even if the original board still works.

However, almerac has a point that if you were going to use a PCI card with modern drives, the performance will suffer a little in some scenarios. My ideal is a PCI Express SATAII card, or if you get a good price, buy a pair of them and put in your two most favorite systems.
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December 11, 2006 2:26:02 PM

Quote:
I hear onboard RAID is not as effective as aftermarket PCI controllers.. Any experience on this???


yes i do have experience on this, and the short answer is no, there is no real difference. there might exist, in some parts of the world, crappy no name north bridges, that support raid, but really just have software raid, but as long as its an Intel or an Nforce chipset, its a hardware level raid, and it will perform as well as an ad in card, if not faster in some instances because of hte lower latency from the north bridge, compared to an ad in card that has to go through the PCI/PCix/PCie bus then the northbridge, then to the processor.
altho realistically, you would need a RAM drive to test that, because hard drives are far to slow to push the bandwidth.

This is true (that there is essentially no difference) for RAID 0 and RAID 1 implementations, but not RAID 5.

Software controllers/on-board controllers do the XOR parity calculation required for RAID 5 in software, which takes a lot of CPU power and severely slows down the write speed of the array.

Hardware controllers have dedicated processors for doing the XOR calculation and will outperform motherboard/software controllers by a long shot.
Anonymous
a b G Storage
December 11, 2006 3:28:33 PM

One of the huge aftermarket advantage, that not many people seam to mention is the fact that if you sell you motherboard, or if it dies, you will need the exact same board or at the very least the same northbrige/integrated raid chip just to access your data.

Aftermarket makes changing mobo a breeze since you move the card with the HD. That is a big +.

I do think performance wise there is a difference, worth the xtra money just for the performance? not to me. But then again I don't think something else then onBoard audio is worth the extra money so it's a personal thing!
December 11, 2006 5:01:15 PM

Quote:
I hear onboard RAID is not as effective as aftermarket PCI controllers.. Any experience on this???


yes i do have experience on this, and the short answer is no, there is no real difference. there might exist, in some parts of the world, crappy no name north bridges, that support raid, but really just have software raid, but as long as its an Intel or an Nforce chipset, its a hardware level raid, and it will perform as well as an ad in card, if not faster in some instances because of hte lower latency from the north bridge, compared to an ad in card that has to go through the PCI/PCix/PCie bus then the northbridge, then to the processor.
altho realistically, you would need a RAM drive to test that, because hard drives are far to slow to push the bandwidth.

This is true (that there is essentially no difference) for RAID 0 and RAID 1 implementations, but not RAID 5.

Software controllers/on-board controllers do the XOR parity calculation required for RAID 5 in software, which takes a lot of CPU power and severely slows down the write speed of the array.

Hardware controllers have dedicated processors for doing the XOR calculation and will outperform motherboard/software controllers by a long shot.

yes this is true, i should have been a bit more thorough, the nforce 4 chipset and higher supports SOME raid modes, most support at least 0, 1, 5, and JBOD. you would honestly need to look at the exact specs of that northbridge, to be able to tell. i would aslo agree with others that it would be a bad idea to depend on that specific northbridge for data integrity. its also worth noting that ad in cards often have a plethora of extra features, and extra software for rescuing arrays gone bad. my original point was simply that, the average person will not see the difference between an a chipset raid or a separate controller. also worth noting is there are some motherboards (usually workstation or server class) that have actual dedicated RAID chips on them, that are not part of the northbridge/southbridge solution.

what kind of raid system are you planning on setting up? because that is what will determine whether or not you should use onboard or an ad in. if you just want to RAID two discs in raid 0 then there is no point in an ad in controller, because you have no integrity, and just raiding two discs hardly justifies a $150 controller.
December 11, 2006 5:45:09 PM

Can you speak at all to the Intel ICH7R southbridge? I am currently using that for a 1 TB RAID 5 array. Write speeds are slow, but not nearly as slow (nor with as much CPU overhead) as I might expect with a software-based solution.

I have clocked writing to the 4-disk array at up to 10 MBytes / second. That is with the Windows write cache disabled. CPU utilization does not vary perceptibly between write and non-write periods.

Mind, I would not use this RAID 5 implementation for anything like TV recording. The peak may be good, but the lowest-observed rates can be pretty bad. It's great for anything involving reading, though (e.g. your online CD collection), because it acts like 3-disk RAID 0 in read mode.
December 11, 2006 6:35:55 PM

Quote:
Can you speak at all to the Intel ICH7R southbridge? I am currently using that for a 1 TB RAID 5 array. Write speeds are slow, but not nearly as slow (nor with as much CPU overhead) as I might expect with a software-based solution.

I have clocked writing to the 4-disk array at up to 10 MBytes / second. That is with the Windows write cache disabled. CPU utilization does not vary perceptibly between write and non-write periods.

Mind, I would not use this RAID 5 implementation for anything like TV recording. The peak may be good, but the lowest-observed rates can be pretty bad. It's great for anything involving reading, though (e.g. your online CD collection), because it acts like 3-disk RAID 0 in read mode.


no i cant, i actually have no personal experience with intel chipsets in RAID, i am just aware that most of the more recent ones have RAID capability. i am much more familiar with the Nforce chipset, ive been using it since socket A. your setup looks like its falling on a software raid or something or the raid chip is not quiet up to par. 10MB/s? thats kinda abysmal my single seagate 7200.10 averages 61MB/s ish according to sandra lite 2007. i have never experienced that problem with my Nforce 4 chipset and ive done RAID 0, 1 with them. idk about raid 5 tho, never had a need for RAID 5. ive used JBOD tho, without any noticeable performance hit (no real performance gain either).
Anonymous
a b G Storage
December 11, 2006 6:42:41 PM

Raid 5 writing is really not fast, data has to be written on 2 disk and parity is also written. It's like a raid 1 but without loosing as much space...

It is pretty normal to see such slow write speed, and that is why a dedicated card with a XOR engine will make the write speed so much faster.
December 11, 2006 7:00:24 PM

That's been my experience so far. Intel claims to use what they brand as "Intelligent RAID". But from what I understand, that means each write is actually a read-modify-write cycle, all occurring within the controller.

Is 60 MBytes / sec a typical write speed for a standalone SATA disk? Or is it 60 Mbits / sec?
December 11, 2006 7:09:59 PM

Megabytes is what i was refering to, and yes, it is around normal for a single disc these days.

if speeds as slow as 10 megabytes/s second are normal for raid 5, i guess it isnt that suprizing, still, that seems really slow.
Anonymous
a b G Storage
December 11, 2006 7:11:11 PM

TOms HD charts

That's in MB/s

Quote:
Acronym Definition
MB/S Megabits Per Second
MB/s Megabytes per Second


Quote:
Upper Case "B" for Bytes
MB/sec, MBytes/sec, MB/s and MBps means megabytes per second and is used for disk and tape transfer ratings.

Lower Case "b" for Bits

I think the upper case 'B' is the real one, making the 'S' upper/lower is stupid, safe to assume they talk about Bytes though!

I would assume it is slower to write and all on the RAID5...
December 11, 2006 7:39:31 PM

Quote:
if speeds as slow as 10 megabytes/s second are normal for raid 5, i guess it isnt that suprizing, still, that seems really slow.


Please don't take my word for this as being normal. This is just what I think I'm getting.

I asked for the clarify on bytes vs. bits b.c. some posters mean one thing and say another.
December 11, 2006 7:40:33 PM

Don't know how he was testing it. But if he's transfer file over 100baseT that is max it's going to get.

It highly possiable he does not have enough ram and cpu power to go any faster. Raid 5 parity calculating requires a lot of cpu (2+ghz) to do parity calculations. My Snap 4500 has a 2.4 P4 in it, 2 gigabit ports, and can send and receive close to 160+Meg/sec.

Hardware raid off load the work to there optomized cpu to do parity calculations. If they fail you are in the same boat. You have to find a card that matches what you had.
December 11, 2006 8:50:03 PM

Quote:
if speeds as slow as 10 megabytes/s second are normal for raid 5, i guess it isnt that suprizing, still, that seems really slow.


Please don't take my word for this as being normal. This is just what I think I'm getting.

I asked for the clarify on bytes vs. bits b.c. some posters mean one thing and say another.

ok, if it was me i would look into that, just to see if there was anything i do to make it a bit faster, (single) hard drives haven't been that slow for almost a decade, would be nice if at least an array meant for mass storage was responsive to a degree.
December 11, 2006 10:35:42 PM

Quote:
I have clocked writing to the 4-disk array at up to 10 MBytes / second. That is with the Windows write cache disabled. CPU utilization does not vary perceptibly between write and non-write periods.


10 MB/sec writes is about typical for a software RAID 5 implementation. Some cards/chips are a little faster, some are slower. If you do software RAID 5 on Windows 2003 Server, this is also about the speed you get.

The top of the line hardware cards (like the 3Ware 9590SE) can do RAID 5 writes at over 100 MB/sec.
December 13, 2006 10:47:15 PM

Sorry I took a while

I have a P5N32 SLI deluxe with an onboard Nvida RAID...

I hear that expensive PCI RAID controllers (>50 bucks) are better than onboard RAID preformance wise.

I plan to setup RAID O (striping) with a couple of WD raptors to speed up load times and data transfer times etc etc.

(still open to discussion)
December 14, 2006 11:41:49 PM

Quote:
Sorry I took a while

I have a P5N32 SLI deluxe with an onboard Nvida RAID...

I hear that expensive PCI RAID controllers (>50 bucks) are better than onboard RAID preformance wise.

I plan to setup RAID O (striping) with a couple of WD raptors to speed up load times and data transfer times etc etc.

(still open to discussion)


i think onboard raid will be fine. you are doing raid 0 so there is little point in an ad in controller, even an expensive one wouldnt make that much of a difference speed wise or integrity wise. altho i would advise you if, your going to get sever raptors (i assume you mean 3 or more) then you might be better off getting 2 (or more) 15000 RPM SCSI drives (they would beat the pants off of any raptor), and a cheap raid controller for them (it would be faster then raptors without so much wasted space, because with an ad in card or not, you should not depend on a raid 0 for data integrity) its also worth noting that the 36GB raptors are not worth much anymore, because most modern hard drivers are faster then them.

also $50 is a cheap raid controller (and i would not expect it to be any better then a chipset), often good ones are more then a hundred, and really good ones are several hundred (USD$), up to enterprise level ones which can be over a grand.
!