Let me make sure I've got this right, re: Raid 5

[compuwiz1]

I'm setting up a box with an AMI U160 raid controller and 4 Cheetah X15's. The 18GB Cheetahs are showing up in FDISK as about 35GB. So it it not showing the capacity of 4 drives, as a single volume because it is spanning, but also mirroring pairs at the same time...correct?
2 drives show same capacity. In building the array, all 4 are identified, however.

 

[fastvideo]

i love you link, do you mine to tell me where you get all those done, i would like to have a multi language web page too.

 

[Tripleshot]

It doesn't sound right for a raid 5 hookup. On raid 5 you would have all HDDs' seen but capicity would be limited to the size of 3 because 1 is for parity. That doesn't add up to 35. Should be closer to 54.

I'm a little confused on this as I have not set one up yet, but that's my undersrtanding. I hope to see someone more knowledgable refute or co oberate this. If it where Raid 1, that would be showing 35 gigs.

 

[OpalFrost98GT]

Right...Raid5 will use one drive for parity...so 4 18gb drives willhave a 18gb x 3 = 54gb usable volume. you should be able to verify this in Windows 2000 under disk management mmc.

 

[Saltin]

If I understand you correctly you you have four 18gb drives.
If you put them all into a RAID 5 array, your total size would be (4x18)-18 = 54. Tripleshot has the right idea.

If you spanned them without parity, you would have 72 gb total.

If you mirrored them all ( and I don't know why you would do this), you would have 18 gb space.

You could span two drives no parity, for 36 gb, and then mirror that span on the last two, but this is not a better option than a straight out span with parity, size wise.

It's been a while since I've done any RAID stuff, so let me know if I'm off at all anyone.

 

[ChrisIsBored]

Saltin you're pretty much on target except i've never seen any RAID controller actually attempt to mirror 3 drives from the first...

RAID 1 usually means an even number of drives, 2, 4, etc... be it in this case, 2x 18G would be the actual data, and the other two would be the mirror...

For standard user desktop environment RAID 1 is both inefficient and not necessary. More suitable for "just in case" backup for your database or other large file environment.

RAID 0 should actually be the best bet for any standard desktop environment provided that you're positive you have sufficient cooling for the drives. If it's your home box, RAID 5 isn't necessary NEEDED, but just there for added security if a drive fails. Look at it this way, if your last system was a single IDE drive and you never had any sort of backup, and you'll be doing pretty much the same stuff just on a faster computer, then RAID 5 will only hinder your performance and RAID 0 will do just fine.

If you do feel you want the added security of parity, and this system will be a desktop environment rather than server orientated, see if your RAID card will let you do RAID 3 instead. RAID 5 is a bit slower on the writes I believe...

 

[compuwiz1]

The main OS drive is completely separate, it boots from an Adaptec U160 controller, running a single 9GB Cheetah. The raid drives are for handling other stuff, and other apps. There are 5 drives in total, but 4 on the raid controller. BTW, this box is gonna be expensive by the time it's done. It's an A/V workstation.
Crap, I've got the array set up, and in the scsi bios on card, I can access the onboard utility to build the array. It does say no logical drives defined. Wouldn't this be an Fdisk function? Well, Fdisk does not see the drives either. What the hell am I supposed to do now? I can find the C driive, install win2k, but when I load the AMI megaraid controller driver, there are no drives in win2k.
Id's are 0,1,2,3. All show in the raid bios utility screen.

 

[ChrisIsBored]

initialized it yet?

 

[compuwiz1]

Ok, logical drives defined and it is initialized, now I have a different problem. Getting it to boot from the stand alone drive. The raid controller seems to want to take over and put the first controlller, which the boot drive is on, secondary.

 

[ChrisIsBored]

If it we're me, i'd put the OS on the RAID drives... it would be faster... but in what order do you have your SCSI card and RAID card in on the PCI slots?

Try having the SCSI card higher up... this sometimes can be the problem.

See if that helps...

 

[compuwiz1]

It's all set. Moving the cards around seemed to do the trick, or else when I just had the scsi controller and Fdisked the drive, then added the raid controller later. At any rate, it all works great now.
The reason for not putting the OS on the array, is that he wants it set up so he runs the OS and some personal stuff on the one drive, but will install all his apps on the raid.

This system has dual P3 1GHz and 1GB of Rambus, as well.

 

[ChrisIsBored]

Sweet.. sounds close to the new server i'm building...

Dual PIII 1Ghz on a Tyan Tiger 230 board...
5x 9.1G IBM 36LZX SCSI drives in a RAID 5 array
1.5GB PC133 Registered ECC RAM
2x 80G 5400 RPM Maxtor D540X IDE drives..(extra storage)

Haven't figured out a backup solution yet though...