What about RAID 1.5?

[mpichescs]

Tomshardware did a review (five years ago) about Highpont's "RAID 1.5" chip used on a couple of motherboards. It's a configuration that offers the security of RAID 1 but with the speed of RAID 0 with only two hard drives. This is, of course, in theory. It seems like a perfect "poor mans" RAID to me. I can't afford 4 hard drives to start a 1+0 and I couldnt even fit them in my case even if they were affordable (only 3 bays).

Why can't something like this be developed? The review at Toms was a little optimistic but in five years no other company has tried it out (a quick look at Highpoint's web site shows they dropped it altogether). Why do manufacturers support 1+0 but not this? Is there some obvious hurdle I've overlooked? Or better yet am I just an idiot and this exact thing I'm looking for exists and I just haven't found it yet? (I really hope I'm that idiot)

What do you all think?

 

[3NZ0]

Intel do it and have done it for years, it's called matrix raid.

Eg. you put in two drives, split the drive into two partitions, 1st half is in raid 0 with the other drive and the second partition is in raid 1 with the other drive for redundancy.

I have only used it a few times, even then for a short period of testing but I would assume the problem arises when you start to put heavy workloads on different partitions, at the same time. You would get a severe slowdown, something you wouldn't get if you had 4 drives, 2 in raid 0 and two in raid 1.

Most people want either speed or redundancy, I myself have 5x80gb drives in raid 0 for speed. This is because they were dirt cheap when I picked them up for a high throughput and their combined capacity is enough for an OS drive. The whole machine is backed up to a fileserver every two days anyway, so I'm not at all bothered about any loss.

On my server I have my drives in raid 5 as redundancy is the name of the game. Matrix raid doesn't really have a place in any of my systems.

 

[Ockie]

You won't have the true speed of Raid 0 since you are basically using the same disk twice. In theory this is nice, but in practice, you are better off with real raid solutions such as Raid 0, Raid 1, or if you wanted 3 drives and have some speed + security Raid 5.

 

[mpichescs]

Im a terrible consumer because the motherboard Im using now supports matrix raid and I had no idea. I wouldnt have known what it was anyway.

So this is definitely interesting. A little information Ive uncovered about it recommends putting an OS on RAID 1 and games and video files on RAID 0. 3NZO do you think you would still suffer from a slow down if I was to put each array on it own platter? I dont know much about the mechanics of hard drives but wouldnt that eliminate the possibility of one head having to read from both arrays? So in effect a smaller chance of slow downs?

RAID 5 looks like an interesting choice as well, just gotta save up a little more than I thought.

 

[StarTrek4U]

So this is definitely interesting. A little information Ive uncovered about it recommends putting an OS on RAID 1 and games and video files on RAID 0. 3NZO do you think you would still suffer from a slow down if I was to put each array on it own platter? I dont know much about the mechanics of hard drives but wouldnt that eliminate the possibility of one head having to read from both arrays? So in effect a smaller chance of slow downs?

No since you can't specify what HD platter to put information on. As previous posters have stated, you'll want dedicated disks depending on your RAID setup.

 

[[LYL]Homer]

I thought RAID 1.5 was RAID 1 on write, but on read it pulls from different sectors of both drives. Hence "poor man's RAID 0" - but only on read.

 

[unhappy_mage]

3NZO do you think you would still suffer from a slow down if I was to put each array on it own platter? I dont know much about the mechanics of hard drives but wouldnt that eliminate the possibility of one head having to read from both arrays? So in effect a smaller chance of slow downs?

No. All the heads seek to the same place on their respective platters at once. This wouldn't help.

I thought RAID 1.5 was RAID 1 on write, but on read it pulls from different sectors of both drives. Hence "poor man's RAID 0" - but only on read.

Any decent raid 1 implementation will do something like this. Reading the Tom's article (shudder) it looks like that's all they're doing, they just slapped a marketing name on it.