Running Raid 0, under Raid 1?

[IAIHMB]

This topic isn't really important, but I just had a thought. :P Is it, or would it be possible to run 2 hard disks in Raid 0 under Raid 1 with another drive?

[Capmaster]

This topic isn't really important, but I just had a thought. :P Is it, or would it be possible to run 2 hard disks in Raid 0 under Raid 1 with another drive?

Sure, if your controller supports it. Theoretically once the drives are Raid0, they become like one large, fast drive. The controller should be able to treat the two striped Raid0 drives as one, and raid the unit together with another pair of striped raid 0 drives as a redundant drive. Then you'd have speed and data security

Check the Adaptec website for how to do that.

Or you could get a single 15KRPM U320 SCSI instead of the two raid0 IDE drives. The U320 will still be faster. Then just raid two together as raid 1 Less power demand and heat also. Problem is you might need PCI-X for U320 :P

[Skoorb]

So you want 2 X 50 gig in RAID0 and 1 X 100 GIG RAID1 to be a redundant source? If that's possible the write speed would be limited by the 1 X 100, so you might as well have just had 2 X 100 RAID 1 in the first place

There are several raid configs, and I'm not familiar with them, but this says that for desktop users RAID0 is insignificantly faster: http://www.anandtech.com/storage/showdoc.aspx?i=2101

[studtrooper]

Well, if you think about it for a second you'd probably figure that to be nearly impossible. What RAID-1 does is send the same information to 2 sets of drives at once (1-to-1, 2-to-2, 3-to-3, etc) for data protection. RAID-0 stripes data to 2 sets of drives for speed increases. So, 2 HDDs in RAID-0 would nearly combine both the HDDs speeds while RAID-1 doesn't increase any speeds at all. Soooo... If you tried to RAID-1 a RAID-0 array you would theoretically need a HDD fast enough for the RAID-1 to concurrently catch the data that is being thrown out to the RAID-0 array (Which, if such a HDD did exist, would negate the need for a RAID-0 array in the first place). Short answer. No

EDIT: On second thought, controllers might exist to throttle back the speed the RAID-0 array to allow for RAID-1 to be used with the RAID-0. But if you couldn't get the speed increases from RAID-0, then why the hell bother?

[shelbyGT]

if I did that with my raid 0, I'd have to buy a 240gb drive..... and that doesn't sound cheap.

[IAIHMB]

You have two 240GB drives in Raid 1?

[IAIHMB]

Wait wait wait, I've done even more thinking. :P Since a regular drive couldn't support Raid 1 under Raid 0, could I run 2 drives under Raid 0 as the Raid 1 drive? :P

[ViRaL1]

How it CAN be done...

If you have 2 (60GB) drives set up as a RAID0 stripe in hardware, the OS will see it as 1 (120GB) drive. You can add 1 (120GB) physical drive and create a RAID1 stripe which windows will see as 2 (120GB) drives.

How it SHOULD be done....

Use 4 matching drives and setup a RAID0+1 stripe in hardware.

[shelbyGT]

You have two 240GB drives in Raid 1?

negatory, two 120gb in a raid 0

just how it came that way, and I'm too lazy to go in and partition and stuff...

[rallynavvie]

Holy...
For the purpose of this lesson striping = RAID 0 and mirroring = RAID 1

You can't have two drives striped with another single drive mirroring them. I don't think any controllers support that first off, second it would slow the striped array down to the speeds of the mirrored drive. However there is striping with parity which creates a parity string on a third drive (RAID 4) or across an array of at least three drives (RAID 5). This helps in that it can handle the loss of up to one drive from the array and rebuild the data from the parity string. It isn't as fast as just plain striping because of the overhead required for the parity (not to mention almost requiring a hardware controller to do the parity calculations). Then there is RAID 0+1, or sometimes called RAID 10 (which it should be RAID 01). That's taking at least four identical drives and striping to two pairs, each pair mirroring the other. Nested RAID, as they're also known, are usually the best arrays to implement if you have the money. I run nested SCSI on my file server for speed and reliability, though the boot is actually only mirrored since I can't afford four 74GB 15krpm U320 drives

I can go on if you like. I've done a small amount of studying on RAID. It gets pretty confusing, especially since a lot of companies mislabel their RAID labelling to whatever is the closest variant that is common/popular. Usually I just paraphrase it like:

RAID sucks unless you're mirroring somewhere in there

or

striping isn't worth the risk for the performance increase, especially with cheap IDE hardware, unless you're mirroring the data somewhere in there

[mrtristan]

Just throwing in my two cents.

Like those quotes rally provided, striping isn't worth the risk, unless it's mirrored somewhere. With two drives in a RAID0 array, you effectively double the possibility of failure. It only takes one drive to kill all your data that's spanned across both.

[shelbyGT]

I'm not worried. The only "large" data I have on there that could get lost are all of my songs (33 gigs wort). All of which are on my iPod and another old computer hooked up to the entertainment system.

Sure, I'd lose some files that I would be a little miffed at, but not much.