RAID Question

[tameanaka]

Hey, I;m going to buy an ASUS P5GD2 Deluxe pretty soon here and was just wondering if the serial raid is an actual hardware raid controller and does all the work without the cpu or is it totally software or is it a combination? If it's not a full on hardware controller, would it be worth it to invest in one? Is the difference between hardware and software negligible? Running ide is totally software isn't it, or is that combination? I'm a noob so be prepared for some other questions to follow up your responses, thanks.

 

[Crashman]

All the onboard RAID controllers I know of are software RAID. The RAID controller is a piece of hardware, but it's just a drive interface, the processing is done by the CPU. I don't know of any reasonably priced hardware RAID controllers either, even add-in cards that most of us can afford are software RAID.

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[tameanaka]

but is there really a noticable difference between the two? it can't be anymore cpu drain than normal ide would use right?(i'm assuming ide hd are controlled through software with cpu)

 

[Crashman]

The "hardware RAID" cards I've used have been SCSI and had both a SCSI controller chip and a RISK processor (usually the Intel i960 RISK processor). The processor does the work of splitting/combining files (not too difficult) and calculating parity for modes 3 and 5 (more difficult). At any rate, RAID0 will eat up CPU cycles using a software RAID, I'm not certain how many, but it wouldn't be nearly as bad as more advanced modes.

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[tameanaka]

Yeah i'm just planning on raid 0 with two seagates. But I guess my question still remains: would the software at raid 0 use more/less cpu cycles than normal ide would? Or would it be worth it to get a promise card? I see on newegg that they have a sata raid card with 2 jacks for only like $60, perfect for my application, but i don't know if i should get it since i haven't foudn the answers to my questions yet.

 

[Crashman]

1.) Software RAID0 will always eat up more CPU cycles than no RAID because the CPU has to calculate the file split
2.) A Promise controller on the motherboard should have similar or identicle overhead compared to a Promise PCI card using the same chip, both software RAID.

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[Codesmith]

I don't think you will likely notice the performance hit at all, and you will see some improvement over IDE just not as much as if you had a $200+ card.

Any any performance hit will only happen when the RAID array is in use. So I am guessing that games will still load faster since durring loading usually the hard drive is the bottlenech and not the CPU.

One interesting note is that Highpoints software RAID 5 on its RR 404 & 454 is pathetically slow. 1/3 the speed of regular IDE (Windows XP software RAID 5 is quite faster).

RAID 5 support was added after the fact via a bios upgrade, but even their tech support advised against actually using it. Advising me to avoid RAID 5 unless I was going with one of their cards with hardware support (RR 464).