Matrix Raid Question

[Psychotic Emu]

I am planning a storage upgrade and was unsure about what to get... until I started thinking about matirx raid when I became utterly confused!

There are so many options!

So many questions but my main one is:
Is it possible to use all the storage space on un-matched drives (in terms of size) using matrix?

ie 2*250gig + 1*200 gig into, for example, a 600gig (3*200) raid0 and a 50gig raid 1

like this but utilising all space


Thanks!

[Psychotic Emu]

Common Guys

[this_is_gav]

I've not used it before, but I'm fairly certain the ICH8R would support JBOD (Just a Bunch Of Disks).

On past experience of other RAID controllers, I find it hard to recommend RAID 0 on different sized disks, and obviously RAID 1 wouldn't work. No idea about RAID 5.

[Psychotic Emu]

I didn't realise there would be a problem using raid 1 different disk sizes. I thought that it would just leave some space unallocated.

Because I know you can have 2 raid types on a Matrix array (available on the last couple of intel controllers) I was hoping that it would be possible to not use all the disks on all of the arrays...

Ideally I dont want to waste any space either

[Agent]

It'll just do 2 * smallest drive size for RAID 0, and 1 * smallest drive size for RAID 1
You can mix drives fine on most RAID controlers. Just easier to have them the same.

[Psychotic Emu]

Cheers guys for the help, I do need it.
I understand basic RAIDs, but its just this intel matrix which gets me confused.

I want 3 drives, with a with a striped array AND a mirrored array on the same disks.

For example:
3*200Gig drives
Half of each drive is striped (ie 3*100)
and the other half is mirrored (ie 1*100) mirroed accross 3 disks :S
(just an example)

In reality what I want is more complicated due to the unequal drive sizes:
Like Adrian's (thanks Adrian ) picture from my first post but with the unallocated space being used in a RAID 1

Difficult to explain! Thanks for reading

[dancingmatt]

You want 1*100 mirrored across 3 disks? So 100GB of data, and then two backups of it? Why would you want to mirror one drive twice?!

In a 2 drive mirrored (RAID 1) array, you have two (partitions of) drives holding the same data so that if one drive fails, your data isn't lost as you have it all duplicated on the 2nd drive. I'm not sure you can mirror one partition three times. Are you expecting to lose two drives simultaneously, which is why you want a third drive in the mirror array?

Losing a drive and a backup of that drive would be massively unlucky. If you've got really old drives and you're worried about them failing, I guess it makes sense, but new drives are so cheap now and yours are 200GB so they can't be that old.

First thing to check is whether you can have 3 drives in a RAID 1 mirror array, and I don't know if you can. Assuming it's possible then like it was said above, striped (RAID 0) arrays are a multiple of the smallest partition in the striped array, so you want to assign the same partition size on each of the disks. Ditto with the mirror array. But you can have different partition sizes for your striped array than you have in your mirrored array.

Time to start googling your RAID controller I think...

Hope this helps

DM

[FInalD]

What you are sujesting is basicaly rather a foolish way to RAID. As is stated by dancingmatt if you lose one drive you'll lose your data.

If you want a striped and mirrored array you should have one set of discs for each, for example what I plan on doing is;

4*320GB drives in total

2*320GB striped
2*320GB mirror of the striped array

RAID 0+1, or 1+0 (can't remember of the top of my head)

This means I will have a logical 600GB (roughly due to formatting), and a backup copy of the logical drive. So if one of my drives dies I will not lose all my data and I can quickly and easily replace the faulty drive.

Using the method you are sujesting sounds rather dodgey to me and seems that you'll mess the system up if one drive dies.

The way the striping works is that all the drives will be limited to the size of the smallest disc, as far as I am aware disabling the remaining part of the disc anyway.

Correct me if I'm wrong...I can just go ask my lecturer about it as we've just covered RAID on my course.

Oh yeh, and something that's labled 'Intel'...well, I'd avoid it, unless it's a Conroe

FinalD

[dancingmatt]

The idea behind Intel Matrix Raid is you take two drives, split them both into two partitions, then set up a striped array on, say, the first partition of both disks, and a mirror array on the other partitions. If you lose one drive you'll lose the data stored on the striped partition, but not the mirrored partition.

So you put uncritical data, like your Operating System, programs, games etc. on the striped array for speed. You put your files, music, photos, docs, whatever - the stuff that you absolutely want to back up - on the mirrored array. You gain (some) speed in operating and using programs since data comes from both drives in the striped array, and if one disk dies you lose your whole system (half your OS etc. has gone) BUT you still have your data on the mirrored partition.

So you gain (some) speed, until a disk dies, then you lose the software installation (which would happen anyway if you only had one disk) but retain your data (which wouldn't).

I've never thought to try it over 3 disks, but having 2 backup partitions in a 3 drive mirror array, if possible, seems excessive to me.

And note - often overlooked - that you gain speed in reading and writing data stored in the striped array, but you can also gain the same speed increase from reading data in the mirror array since that can be streamed from both disks. Of course, you lose speed in writing to the mirror array since you have to write to 2 disks.

DM

[FInalD]

You may aswell just use the smaller drive for Windows, and then mirror the other two drives for data backup, as you have three this easily is possible and losing a Windows install isn't as upsetting as losing data.

FinalD