PATA RAID questions

[lowereastside]

Hello all,

I am getting ready to set up a couple RAID arrays and would like to run my configuration ideas by you all to see if things look right.

First, my hardware:
Epox 8RDA6+Pro motherboard
nVidia nForce2 ultra 400 chipset with Gb LAN and RAID
2 Western Digital SATA 36Gb hard drives
2 Western Digital PATA 120Gb hard drives

And here's what I'm thinking:

---A striped array consisting of the two SATA drives for the OS, program files, page file

---A striped array consisting of the two PATA drives for all my data

---A WD 320GB external hard drive for frequent backups, as I know striped arrays are risky

My main questions are about the PATA RAID array:

1. Should each drive be a master on it's own IDE channel?

2. Assuming both PATA drives are masters on separate channels, How will putting my DVD drive as a slave on one of the channels affect data transfer when the DVD drive is in use?

3. Is it true that modern IDE devices are no longer limited by the speed of the slowest device on the channel, as used to be the case? Or would my hard drive have to operate at the same speed as the DVD?

Thoughts, suggestions, answers anyone?

Thanks,
Andrew

[BipolarBill]

1. Moot question. Most onboard PATA RAID controllers have a single port. If you have two, set them each as master.

2. No can do - CD drives can't be detected on RAID controllers.

3. Not really. Always set fastest device as master.

[lowereastside]

Thanks for the response.

I'm a little confused about your answers to my first two questions:

On the Epox 8RDA6+Pro, the RAID controller is integrated into the southbridge of the chipset, the nVidia nForce2 Gb RAID southbridge (the final edition of this chipset).

In the motherboard BIOS the options are as follows:

IDE RAID BOOTROM [enable/disable]
IDE RAID [enable/disable]
IDE Channel0 Master RAID [enable/disable]
IDE Channel0 Slave RAID [enable/disable]
IDE Channel1 Master RAID [enable/disable]
IDE Channel0 Slave RAID [enable/disable]
SATA Primary Master RAID [enable/disable]
SATA Secondary Master RAID [enable/disable]

Once enabled, each device becomes available in the nVidia RAID BIOS to be incorporated into an array.

So would it not be possible to enable RAID on the IDE Channel 0 & 1 masters, leave the IDE slaves disabled, and in this way have a RAID hard drive and DVD drive sharing the same IDE channel? I sure hope so.

[BipolarBill]

Your motherboard is an exception to the rule which states that onboard PATA RAID controllers do not support CD drives.

There's need to disable any ports or channels. Set up your SATA and PATA arrays (use the master setting for each IDE drive) and then connect your CD drives as unassigned slaves.

Frankly, I don't like to encourage striped arrays for home use. Something *will* go wrong sooner or later and you will either lose Windows, your data or both. Since performance gains of RAID over non-RAID are in the area of 15%, it sure aint' worth it from even the materials standpoint - much less data integrity. I have RAID available on all of my systems. Do I ever use it? No. RAID 0 doesn't offer enough performance to justify the risk and RAID 1 doesn't make sense when I can use the extra drive(s) and Norton Ghost to do regular scheduled backups.

[lowereastside]

Yeah, I'm one of those freaks who tries to squeeze every last drop of performance out of his rig even if it doesn't make much sense. I'll take that 15%! Especially on this mobo, where the RAID isn't limited by the PCI bus.

But I appreciate your advice and the clarification on the CD/DVD issue.

Thanks again.

Andrew

[Midknyte]

why would you want 2 RAID0 arrays? that doesn't make sense to me.

[lowereastside]

Well, that's a good question, and one that tests some of my assumptions:

One being that RAID works best with identical drives.

The other being that using drives of different sizes in striped arrays would result in wasted disk space.

I already have two WD 36Gb Raptors.

And then I have a WD 120Gb PATA drive. I plan on getting another WD 120Gb PATA drive.

I'm doing RAID purely for the performance gains, which I know are not great on single-user home systems; but for the kind of applications I use, such as video and audio recording, which use very large files, sustained access to a particular part of the drive can be improved quite a bit with striped arrays. A lot of the delay in hard drive access comes from the time it takes the drive head to reach the part of the disk to be read. It takes much much longer, relatively, for the drive head to move than it takes for the data to be transferred to RAM. So even if you improve the transfer rate with RAID, if you're reading a lot of small files dispersed over the drive, you're still dealing with the time it takes to reposition the drive head, and RAID doesn't help with that at all, as far as I know. But with reading/writing large files (especially with reading/processing large, unfragmented files), my past experience with RAID is that there are noticeable performance gains. Additionally, you can reduce the neccessity for drive-head movement by partitioning your drives in ways that compliment your applications.

For some time I have been partitioning my systems in such as way as to put the OS and program files on a different drive (and drive channel) from my data, so that the system can access programs and data simultaneously, with a minimum of drive-head movement. So I plan on expanding that idea and having one SATA RAID array for the OS & programs, and the much larger PATA RAID array for all of my data--and in so doing, take a bite out of transfer time and seek time.

(But, as Bill has pointed out, RAID 0 is risky, having several more possible points of failure than non-RAID systems. So it's absolutely essential to proceed on the assumption that the array WILL fail, and to have a good backup routine in place at all times.)

Now, if there's a way to have a four-disk RAID 0 array with two 36GB drives and two 120GB drives and not waste huge amounts of disk space on the larger drives, I'll definitely consider that. But even it's possible , I'm not sure that makes much sense.

Anyway, that's my thinking.

Andrew

[lowereastside]

By the way, no one has actually answered my original question #2, which was:

Assuming both PATA RAID drives are masters on separate channels, How will putting my DVD drive as a slave on one of the channels affect data transfer when the DVD drive is in use?

I've heard that only one device controller at a time can have access to the channel. So I'm guessing that when the DVD drive is being accessed the PATA RAID array is going to take a hit. What I'm wondering is how serious that hit will be. Will data access on the PATA RAID array come to a grinding halt if I'm using the DVD drive?

[Midknyte]

most raid adapters will not allow for atapi devices at all.

on standard ide, a cd or dvd would not affect the speed of the hdd unless you are accessing the drive. check out this link: http://www.pcguide.com/ref/hdd/if/ide/confTiming-c.html

yes ide can only access one drive at a time. it really depend on what you are doing, but there is a performance penalty because the computer has to switch time between the hdd and the dvd.

[lowereastside]

Thanks for the link. That's a great site. Some of the info seems a little out-of-date, but lots of good stuff on there.

As suggested on that site, I'm thinking about maybe getting a PCI IDE addin card and putting the DVD on there.

I didn't even realize that was an option, but it kind of makes sense to me, because the speed of the optical drive pretty much matches the speed of the PCI bus, and that way it wouldn't be interfering with my PATA array.

Anyone have a recommendation for a good PCI IDE addin card?

[BipolarBill]

the speed of the optical drive pretty much matches the speed of the PCI bus, and that way it wouldn't be interfering with my PATA array.

BZZZZ! Wrong answer. The PCI bus can handle 133MB/s. No optical drive is going to get anywhere near that. Figure 15MB/s for optical drives.

Highpoint and Promise both have excellent IDE cards. I prefer Promise because they make it a point to allow ATAPI connections.

http://www.newegg.com/Product/Product.asp?Item=N82E16816102026

[lowereastside]

Yes, my mistake.

I was thinking aloud and equated 33Mhz with 33MB/s.

I think I'll try my setup without the IDE card, and just see how it goes with the DVD drive and one of the PATA RAID disks sharing a channel. I'm worried about writing from the PATA array to the DVD drive; it seems like transfer times would really take a hit with them sharing a channel. But if the "hit" is only a couple milliseconds here and there, it might be manageable. I'm also concerned about a PCI IDE card hogging the bus and interfering with my PCI sound card when, for example, playing a CD. We'll see.