4 drives, 3 cables - who goes with whom?

[Felecha]

I was so confident that the guy who built my box at the local computer shop knew it all, now that's a little shaken.

Athlon 900 TBird, ABIT KT7-RAID, 256, 98se. I got a second hard drive so I could use the RAID, so I now have 2 IBM DeskStar 75GXP 30GB. And I got a CDROM and a Plextor 8/4/32 CDRW. On the board, there are 4 IDE controllers -- 1 & 2 are "regular", 3 & 4 are RAID. When it was built, he put the HD on #1 , with the CDRW as slave. CDROM is on #2. 3 & 4 are open. When I got the 2nd HD, I looked inside and saw the setup and was puzzled. The ABIT manual says they strongly urge not to put a CD-ROM on the same IDE channel as a HD, for performance reasons, depending on the CDROM performance. And I thought that 3 & 4 were the hotshot connectors, so the HD would have gone there. I called him, and he said this was his first RAID motherboard installation, and he hadn't read the whole manual word for word. He thought he had seen 1 & 2 as the RAID connectors, and he completely missed the fine print about not putting a CD with a HD.

I can't complain a lot about the performance the way he set it up. It's so fast compared to what I had (200 Pentium Pro). But now I have this second drive, and one more cable, to make a total of three cables available, and 2 open connectors -- the 3 and 4 RAID connectors. I don't know much about these things, but I think I can do the install myself, having read enough on websites. I can install my own RAM and peripherals, just never installed a HD before.

So the quiz is -- with 4 connectors, 4 devices, and 3 cables, what goes where? I can of course just get a 4th cable and each device would get its own connector and cable, and I expect the HD's would get the RAID connectors and the CD's would get 1 & 2.

The manual says not to connect a HD and CDROM together. Does that apply to a CDRW as well?

For now, would I put the HD's on one cable in one of the RAIDs, as master and slave? I plan to use the 2nd HD for installing a Linux partition, and for massive backup capability. Would backups benefit from individual channels for the HD's? If each HD gets a cable and a channel, that leaves the CD's having to go piggy-back. Somewhere I read that a CDROM and CDRW should not go together, it would make copying really slow.

Anyhow, that's my puzzle and what I've thought of it so far. Any gurus out there?

Thanks a lot

F

 

[Pederv]

I've got the same board using 2 IBM 20G's in RAID 0. So I may be able to help. If you're gonna RAID 0 your hard drives you'll need a second ATA66 cable, one for each HD on each channel. If you RAID 1 your HD's then you can leave both on the same cable. If you just want to have 2 HD's then you can connect them either on the same channel or sepperate ones off of #3 and/or #4. It is better to have your CD's on seperate channels for disk to disk copying. Unless ATA has changed and I wasn't paying attention, you can only have one "actively" UDMA ATA device at a time on a channel. I haven't done any benchmarks on devices sharing a channel to verify this, but I'm sure someone out there has.

 

[Felecha]

So, 2 + 2 = 4, as has so often been the case. Looks like I should get a 4th cable and set everyone separate, to cover all possibilities. I don't know what exactly I'll end up doing, and another cable is not a big expense.

Thanks

F

 

[jimmygates]

Since you have 2 hdd's and 2 cd-roms, I would set it up like this.

1 IBM 75GXP 30GB Primary Master on RAID #3
1 IBM 75GXP 30GB Secondary Master on RAID #4

1 Plextor 8/4/32 CDRW Primary Master IDE #1
1 CD-Rom Primary Slave IDE #2

The reason for putting the HDD's on seperate channels is to get the best RAID performance out of them. The performace of RAID with HDD's on the same channel is really pointless.

For IDE, I think the rule is the device on the channel only runs as fast as the slowest device. So with the previous setting, your IBM 75GXP was probably forced to wait for your Plextor 8/4/32 CDRW. With this in mind, if the CD-Rom is slowing the Plextor 8/4/32 CDRW down, maybe you can put it on its channel also. Just my $.02


-Jimbo

 

[Felecha]

Jimbo --

That's what my rookie guess was, but I'm curious about setting the CDROM as a Primary Slave. All the others you suggest as Primary Masters.

Is Primary Master or Primary Slave a meaningless term if there's only one device on a channel?

Thanks

F

 

[Pakman]

You would want to set them all to master if they're gonna all be on different IDE channels.

 

[1ce]

The terms primary master and primary slave just mean what connector the item is on and is it set to slave. Normally, like in my computer, you have two connecters. One being primary and one being secondary. Then on both connectors one can have two drives, one being master the other slave.

To get the raid proformance the drive MUST be on different connecters. On IDE connectors one one drive can transmitted at a time. RAID is when you have two hard disks acting as one and transmitting both at the same time. For example, take the byte (in bit format) 01001101. One drive would send 0,0,1,0 while the other sends 1,0,1,1. The raid controller takes these two transmitions from the hard disks and puts them together to get 01001101.

The best layout of your system would be if all of the drives would have a differnet cable and connector. But in my computer, I am short on irqs and each new connector takes up another irq.

Therefore, You should put the the hard disks on differnet raid connectors, and the Cd drives on different connectors as well. But if you cannot spare the irq then put the CD ROMs together and set the Re-Writer as Master. The problem you might encounter is that you can't copy the CD while writing it because both drives cannot talk to the computer at the same time. Then you would have to copy CD to hard drive then to CD.

 

[Felecha]

Sounds good to me. Thanks, all

F

 

[Mday]

yeah, just set each drive as the master on the channels... ;-)

it's best to have the CD-ROM and CDRW on different channels if you want to do CD cloning.

you need one more cable. that is, a fourth.

the HDDs which are in RAID belong on the RAID channels and should use the ata66 cables (the wires are thinner, and there are 80 wires and 40 pins). the CD-ROM and CDRW can use ata66 cables if you have them, or regular IDE cables are fine (40 wires, 40 pins)