Raid

stan03 · Oct 27, 2003

My motherboard supports
"RAID 0(Data Striping), RAID 1(Data Mirroring), RAID (0+1) and also JBOD function, delivering both data protection and data fetching performance to meet intensive applications demands."(taken from the site.) now i get raid 0 and raid 1 but what is raid 0+1? what are the performace differences between 0+1,0, and1? i know 0 is faster than 1, but i want the security features of raid 1. is 0+1 faster or slower than RAID 1? and i need two drives to do this, i know that much, but in the bios how do i set it to these different types of RAIDs?

deathman20 · Oct 27, 2003

Well think of raid 0+1 as a combination of Raid 0 and Raid 1. It does both if I can remember correctly. You would need 4 drives to do this.

So for example drives 1&2 are in a raid 0 setup, but with Raid0+1 drives 3&4 are in a Raid 0 setup too just mirroring drives 1&2. So you can take this 1 of 2 ways. Its Raid 0 with a mirror, or its a Raid 1 with a nice bump up in writing throughput.

Edit: WOOT Finally a 1 to 1 post ratio. Shows what happens when I get away from the OC'ing forums I lose my posting per day standing.

stan03 · Oct 27, 2003

wow thanks for the quick reply and umm i need 4 drives to do RAID 0+1? i thought at the sticky at the top it only said 2.... but maybe cause i don't get what im reading.... ok.... now how do i change the raid in the bios? and the writing for Raid 1 is slower, but how much slower? is the increased speed of the reading worth the slower writing speed?

another question.... how can i find what kind of sata raid i have? i don't see it on the site. does sata raid work the same way?

deathman20 · Oct 27, 2003

http://www.raidweb.com/whatis.html

This link at the bottom has what the raid setups need for drive wise, and it is 4 for 0+1. Thought I was right.

As for Raid 1 here. Writing should be as fast as the slowest drive if not mistaken. This was taken right from the site above.
RAID 1: Known as "Disk Mirroring" provides redundancy by writing twice - once to each drive. If one drive fails, the other contains an exact duplicate of the data and the RAID can switch to using the mirror drive with no lapse in user accessibility. The disadvantages of mirroring are no improvement in data access speed, and higher cost, since twice the number of drives is required. However, it provides the best protection of data since the array management software will simply direct all application requests to the surviving disk members when a member of disk fails.

As for how its setup in the BIOS, you'd be asking the wrong person

. I only did raid once and had a problem with it. Right now I'm in the process of thinking about another raid setup but I'm waiting on how the new Raptor drives turn out for preformance before I choose to go raid with those right now or just get 1 to start with.

deathman20 · Oct 27, 2003

Oh and your other question, SATA if not mistaken works the same wait ATA raid works. So there should be any problem with that. The Raid setup window should appear right after the bios screen when booting.

stan03 · Oct 27, 2003

why is RAID 1 more expensive? and the reading speed is fast right? thats all i need. is it as fast reading as RAID 0?

shiyan · Oct 27, 2003

I guess mirroring is more expensive in terms of cost per megabyte, as you only get half of the total capacity of the 2 drives.

with regular bunch of disks or striping, you will have the entire capacity of the drives.

read might be somewhat faster than a single disk, not sure by how much though. might be slower than striping though.

deathman20 · Oct 27, 2003

Raid 1 is more expensive because that it uses 4 drives. Besides using the 4 drives say your using 80 gig drives. In raid 0 setup you would have a nice 360 gig array. Yet no data security. With raid 0+1 you'd only have 180 gig array the speed of raid 0 (probley a bit slower due to mirroring) and the security of raid 1 if a drive fails.

Like what I said before about speed is that its totally a ?? unless someone here runs a raid 0+1 array to give us some stats.

deathman20 · Oct 27, 2003

Guess if your controller supports a Raid 5 setup I'd choose that over a Raid 0+1 setup. It only takes 3 disks to set up and it has security and also better transfer rates compared to a Raid 0+1 setup.

pkrew · Oct 27, 2003

Stan, the SATA raid controller on you mobo only support a 2 drive raid array. That means you can't use a 0+1 array. If you want to have a 0+1 you'll have to use the PATA raid controller on your mobo or buy a SATA controller card that supports 0+1

deathman20 · Oct 27, 2003

Oops didn't think of that one

Good call pkrew

stan03 · Oct 27, 2003

ok, well im looking to set up raid with the ata first anyway cause i really only need one raid array... maybe when i get more money ill get the sata raided also.... my ata raid can support 4 drives right? but it cant do raid 5 unfortunately. so what is the difference in read performance between raid 0 and raid 1? i really only want 2 drives, cause it would be a waste of money to get a third

pkrew · Oct 27, 2003

Yes, your ata raid will support 4 drives. I don't really know the difference, but I suspect that the raid 1 would perform similar to a single drive and perhaps slower.

stan03 · Oct 27, 2003

but it will read about the same speed as a raid 0 right?

deathman20 · Oct 27, 2003

In therory it should read the same speed as Raid 0, but I'm not 100% sure on that one.

shiyan · Oct 27, 2003

hmmm... sorry to say this, but it looks like mirroring is a lot slower than striping, and does not seem much faster than 1 single drive...

here's a detailed report on RAID performance:
http://www.tech-report.com/reviews/2002q4/ideraid/index.x?pg=10

pkrew · Oct 28, 2003

Nice link Shiyan. Very informative

stan03 · Oct 28, 2003

which one of those graphs is for the read time only? or is that what they are?

EDIT: http://www.acnc.com/04_01_01.html

it says that RAID 1 writes that same speed as one drive, but reads twice as fast... that would be what im looking for, but does the linky shiyan posted disprove that?

shiyan · Oct 28, 2003

that is what it suggests, but I'm not sure how accurate that is.

I say this because if you look at the graphs for transfer rates at the beginning and end, Raid 1 (mirroring) is significantly slower than Raid 0 (striping), pretty much the same as using just 1 drive.

begin: http://www.tech-report.com/reviews/2002q4/ideraid/winbench-begin.gif

end: http://www.tech-report.com/reviews/2002q4/ideraid/winbench-end.gif

This would make sense, because although there are 2 drives to read from, the length of track on each platter used up to write one file in a mirror array is still going to be the same as that in a regular 1 disk setup, whereas the track length in the striped array with 2 disks would be just half, due to only half the data being sent to each drive. And as the drives are still spinning at 7200 rpms, the time to read the track for the file in the mirror array won't be much different from that of the single drive.

That's just what my interpretation is for what you see in those graphs.

stan03 · Oct 28, 2003

darn... so then there really is no point in running raid 1 huh? it just like running two drives seperate....

and another question for raid is i have 2 120 gigs it would just show up as 1 240.... right?

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