SATA RAID vs. IDE…

[kevinshi]

SATA RAID vs. IDE…

I’m a newbie and yes I have read the FAQ (very helpful thanks for putting it together).

I’m considering buying the Abit IS7-G motherboard which the spec says has:
-> “2 x Ultra DMA 33/66/100 Connectors”
-> “4 x Serial ATA 150 RAID Connectors”

Please tell me whether my understanding of the following is correct:

The “Ultra DMA 33/66/100 Connectors” are:
1) A fancy way of saying they are IDE controllers
2) If I put a HDD that supports a transfer rate of 133 then I will not be getting the full benefit of the HDD

The “Serial ATA 150 RAID Connectors” are
3) the functional equivalent of having added a PCI raid controller card to my system
4) are a hardware RAID solution
5) would not be accessible to me during Windows XP setup unless I inserted a floppy with the proper drivers during initial boot of setup
6) If I put a HDD that supports a transfer rate of 133 then I will not be getting the full benefit of the controller

If all of that is correct then I have some follow up questions that I’ll ask in a new thread… thanks in advance for putting up with me…

Thanks,
kevin

 

[Crashman]

Wrong: The fastest BURST rate I've seen from drive cache is around 110MB/s. The fastest MEDIA TRANSFER rate I've read from an SATA drive is around 102MB/s. So you don't have any limits to worry about, and you don't have a hardware RAID controller either.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[kevinshi]

OK, so I think you are saying that #2 & #6 are wrong in practice. Do I have the thoeretical proposition correct though?

"..you don't have a hardware RAID controller."
Huh? Now I am *very* confused. The mobo says it has four SATA RAID connectors. That's not a hardware solution? Why not?

Thanks,
kevin

 

[Crashman]

The RAID controller is "hardware" but it doesn't have a RAID processor to break up the files into chunks to split between drives. So it uses the CPU for that.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[Codesmith]

Currently (performance) ATA100 = ATA133 = SATA 150.

Even a fastest ATA hard drive, 74 GB Raptor starts out at <75 MB/s at the beginning of the drive and ends at about 53 MB/s.

Of course that Raptor is only avaliable in SATA, but I suspect that it would be just as fast if released in an ATA 100 version.

Advantages of SATA
1) Better cabling
2) Hot Swapable. You can plug an external SATA drive into your motherboard while your system is on.
4) No Mater/Slave.
3) Eventually hard drives will be fast enough to need it.

 

[kevinshi]

"The RAID controller is "hardware" but it doesn't have a RAID processor to break up the files into chunks to split between drives. So it uses the CPU for that."

Ah. Thank you, thank you, thank you.

Thanks,
kevin

 

[kevinshi]

"Currently (performance) ATA100 = ATA133 = SATA 150."

Ah, so given any one of those the limiting factor is going to be my hard drive not the cabling. Correct?

Thanks,
kevin

 

[kevinshi]

"The RAID controller is "hardware" but it doesn't have a RAID processor to break up the files into chunks to split between drives. So it uses the CPU for that."

Hmm. So armed with a bit better understanding I went and looked carefully again at the docs of the motherboard I am evaluating. What I see is both confusing in its own right and doesn’t appear to be totally consistent with what you’ve said.

I’m looking at the Abit IS7-G: http://www.abit-usa.com/products/mb/techspec.php?categories=1&model=81

First, if you take a gander at the tech specs by dialing up [ http://www.abit-usa.com/products/mb/techspec.php?categories=1&model=81 ] you will see the following:

“
Serial ATA RAID
- On board 2 channels Serial ATA 150MB/s data transfer rate
- Supports RAID 0

2nd Serial ATA RAID
- 2 channels SATA 150 RAID 0/1 via Silicon Image PCI Chip
“

Now the fact that it says it supports RAID sure seems to me that they are implying hardware control. Otherwise why would they say that – its just a normal IDE with a different connector, eh?

However if you then go to their user manual (page 36 found at [ftp://ftp.abit.com.tw/pub/download/manual/english/is7_series.pdf
]) they say the following:

“
SATA1 and SATA2 are controlled by South Bridge. To enable the SATA1 and SATA2 controller, you have to enable the “OnChipSerial ATA” first in the BIOS menu of the “OnChip IDE Device."
...
SATA3 and SATA4 are controlled by Silicon Image PCI Chip. To enable the SATA3 and SATA4 controller, you have to enable the item “Serial ATA Controller” first in the BIOS menu of the “Onboard PCI Device”.
“

Here it seems like they are saying that SATA1 and SATA2 are simply IDE controllers w/out any hardware support. Further it seems they are saying that SATA3 and SATA4 are indeed controlled by hardware (the Silicon Image PCI Chip).

My guess is that the tech specs are misleading (but the manual is accurate) – that there are two SATA controllers w/out hardware RAID and there are two WITH hardware RAID.

What says you - am I nuts?

[Begin Edit]

OK I just talked to Abit technical support and the fellow there tells me that all four of these are hardware controlled RAID (user selectable in the BIOS – you don’t HAVE to use hardware RAID).

SATA1 and SATA2 are controlled, he said, by the Intel chipset. SATA3 and SATA4 are controlled by the Silicon Image chipset.

I asked specifically if in any case would the CPU be involved in the RAID management process and he said “no, definitely not, that is the point – there is no software RAID here it is hardware RAID.”

Hopefully no one will tell me this fellow is nuts…

[End Edit]<P ID="edit"><FONT SIZE=-1><EM>Edited by kevinshi on 01/20/05 03:30 PM.</EM></FONT></P>

 

[Codesmith]

Most definately.

I benchmarked my fastest IDE drive (Seagate 200GB) on both a really old Promise Ultra ATA100 controller and my new Abit NF7-S2 motherboard's ATA133 controller and got identical charts both times.

 

[Crashman]

Nah, what you have here is two controllers that are both SATA standard controllers and both have BIOS to enable RAID features using the controller as the I/O device and the CPU as the processor.

I haven't looked at the hardware on any high end solutions recently, but it used to be you'd find on most "hardware RAID" cards a RAID controller and an i960 processor, where the processor did the heavy work of splitting/combining the data (and calculating parity data for modes 3 and 5). Without that second chip, the CPU does the task.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[Codesmith]

Some raid cards do 100% of the work is being done by the RAID hardware.

Then there is software raid where the ATA controller is doing 0% of the RAID proccessing.

Many budget RAID controllers fall somewhere in between with some of the work being done in hardware and some being done in "software" that is executing instructions on your CPU.

For example Highpoints RR404 is a "hardware" raid controller but its RAID 5 is software RAID. This makes it's RAID 5 increadibly slow, in fact it is even slower than a 100% software solution! But the more expensive RR464 has hardware XOR making it much faster than software RAID 5.

Many cheap sound cards, modems, lan cards opperate on the same principle.

 

[kevinshi]

OK, so if I am understanding you all correctly (and thanks again for putting up with me on this) you are saying that the tech support guy at Abit isn’t entirely correct…

That in fact ‘controller’ on the motherboard there does *part* of the heavy lifting but in the end the CPU is used as well. So this is a sort of ‘bybrid’ solution using hardware and software.

So there are three types of RAID:
- CPU does it all -> “Software” (Windows XP Disk Management)
- CPU does some in partner with some other chip -> “Software/Hardware’ (the motherboard I reference above)
- CPU does NONE and other chips do it all -> “Hardware” ($200 PCI add in cards).

Is that correct?

[Start Edit]

Another nuance just hit me…

All I care about is RAID level 0. Could it be the case that the Abit tech support guy was saying that “if you are using RAID 0 then there is no hit on the CPU”?

[End Edit]

Thanks,
kevin<P ID="edit"><FONT SIZE=-1><EM>Edited by kevinshi on 01/20/05 05:30 PM.</EM></FONT></P>