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Mixing RAID types in different partitions

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  • Hard Drives
  • NAS / RAID
  • Partition
  • Storage
Last response: in Storage
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October 5, 2006 3:51:21 PM

Hi all,
Here's the deal. I'm building a new C2D system, and I ran into the following dilema (I'm simplifying it a bit for the sake of clarity). Say I have 2x320GB drives. I want the OS to be in RAID0 while the data is non-RAID. So, I partition each 320 to 20+300, put the two 20G partitions in RAID0, and I'm left with two non-RAID 300 partitions for data.

Now here's the question. Say one of the drives *dies*. Obviously the RAID0 partition is gone, which is ok because it's only OS. The non-RAID partition on the dead drive might also be gone, let's assume I don't care about that. The question is -- what about the drive that did not fail? The data on the non-RAID part of this drive should obviously be intact. BUT will I be able to access it? Specifically, will it be possible to connect this drive to a different system (via RAID or non-RAID SATA controller), or as an external disk, and see the non-RAID partition?

BTW, the M/B will be Intel 965 w/ 6xSATA, RAID controller on board.

Thanks for your help everyone!

More about : mixing raid types partitions

October 5, 2006 6:37:03 PM

Assuming you have a raid controller that supports what you are trying to do, then yes the non-raid partitions are just regular partitions and can be read by any system.

If you are worried about losing data you can use RAID 1 on the data partitions.

BTW every RAID 1 array I ever created allowed the a single drive to be accesssed by any system as a regular drive, and I never hear of a RAID 1 drive having problems when connected to a non-RAID controller.

Still I am very cautious so as soon as I set up the hard drive I would

1) test to make sure I can still backup and restore my OS (some utilities may not have the right drivers for you RAID controller,

2) determine what I need to do to recreate the array wihtout losing data if something trivial happens to it (lets say you start the system with a lose data or power cable) and

3) Verify that your data partition can be read by any system.

And don't forget step

0) running a full diagnostic on each drive before using them. I doubt the drive would be defective when shipped, but you never know how many times the drive was dropped or kicked arround before you recieved it.

And maybe

4) Benchmark the system so you know how much faster it runs using RAID 0.
October 6, 2006 9:59:59 PM

What you want to do is not possible. If you want your OS on a RAID0 you need to buy two HDD's and hook them up in RAID0 config. If you want a separate data disk you'd need to purchase a third disk, or more if you want anonother type of RAID there.

RAID means Redundant Array of Independend Disks (that means physical disks, not partitions). Level 0 means no redundancy. Level 1 is the simplest way and is just a mirror. Levels 3 and 5 spread checksums across the disks so you can rebuild all data if one disk fails. Anything else is a mix of the previous types, i.e. RAID 10 is just RAID 1+0, that is a mirrored stripeset. There are controllers that can mirror RAID5's for increased safety, but usually the ones on a mobo cannot. This type is very rare and requires at least 6 disks, which until recently, was possible only with SCSI RAID controllers.

If you want your OS on a RAID you need to have a floppy drive with the RAID drivers for your controller read and press F6 during setup (a message will display telling you to do so).

Any data on a non-RAID disk is accessible as long as the disk itself has not failed. Any data on a RAID0 is lost if one disk in the array dies. Any other form on basic RAID (1, 3, 5) is safe as long as one disk fails. After that it becomes more complex and is dependant on the type of array in an array.
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October 7, 2006 7:01:07 PM

Its called Matrix RAID.

Technology changes so fast you have to be very careful when you tell someone something is not technically possible.

Pretty cool stuff. You can have only two drives and still use RAID 0 for your OS and RAID 1 for your data. Or you can have 3+ drive and mix RAID 0 and RAID 5.

Last I checked it was only available via Intel motherboard chipsets, but I wouldn't be surprised if Intel released it in some other form or if other manufactures adopted it.

Quote:

Intel Matrix Storage Technology can be found on select platforms based on the IntelĀ® 965, 975X, 955X, 945G ,945P, 945PM and 945GM Express chipsets. Contact the platform manufacturers directly to verify which of their products offer Intel Matrix Storage Technology.
October 7, 2006 8:22:55 PM

Hi guys,
Thanks for all the valuable info! It is much appreciated.

Codesmith I believe you've answered all my questions. Indeed the best thing is to simply configure the thing, then test it and see if the non-RAID partition is seen by another controller. I'll let you know how this turns out. Also, I'm encouraged to hear that it works this way with RAID1 (i.e. you can access each disk seperately via a non-RAID controller). I was actually curious about that.

p.s. Calyn: indeed this is new technology, and I have not yet tried it myself. It seems these new RAID controllers will allow you to have different RAID types on different partitions of the same physical disk, which is very convenient for many purposes. Once I have it configured, I'll share my experience with all of you.

Cheers!
October 9, 2006 8:01:37 PM

Quote:
Its called Matrix RAID.

Technology changes so fast you have to be very careful when you tell someone something is not technically possible.


Intel Matrix RAID is close to what he wants, but not exactly.

Intel Matrix RAID will support 2 logical disks on 2 hard drives, but both logical disks must be some type of RAID. You can mix RAID 0 and RAID 1 logical disks, or RAID 0 and RAID 5 logical disks, or RAID 0 and RAID 10 logical disks. But you cannot create any type of logical disk that is non-RAID.

Furthermore, if the drive isn't connected to an Intel Matrix Storage controller, I don't think you'd be able to see anything. The RAID logical disk definitions aren't written to the hard disk's MBR/Partition table in the standard fashion so that non-RAID controllers could see the logical disks. (This is true of almost any RAID controller, not just Intel Matrix RAID controllers).

The following is a semantics issue/technicality, but I thought I'd mention it. Different sections of RAID are properly referred to as "containers" or "logical disks". "Volume" is sometimes used but it is technically incorrect - a volume is actually a term used by Windows at the file system level. A "partition" is also a file system term - it refers to a section of a drive that has been reserved to create a file system.

So, viewing the storage subsystem from the top down:

Disk Volume (drive letter, as seen in Windows, formatted with a particular file system like NTFS) -->
Partition (section of storage) -->
Logical Disk (seen as one device by Windows) -->
Physical Disk (a single physical hard drive)

RAID controllers create Logical Disks out of Physical Disks.
Partitioning software creates partitions on Logical Disks.
Formatting creates a Volume of a particular file system in a Partition.

Don't mistakenly call a Logical Disk (created with the RAID controller) a "Partition". They are two completely different things, defined at completely different levels in the storage subsystem.
October 10, 2006 12:06:06 AM

Most RAID 1 controllers create a local disc from two physical disc by the most straight forward method.

Each physical disc is the same as a non RAID disc and all the RAID 1 controller does is make sure that they are kept in sync.

Obviously this won't apply to any other RAID version or even RAID 1 setups with more than two drives.

It could also be that most RAID 1 controllers produce individual drives that are non-standard and I have just been extreemly lucky.


I still run tests with every new controller, but so far Two drive RAID 1 Array = complete compatiblity with non-RAID controllers.

---
I would really like to get my hands on a Matrix Raid controller.

I am guessing Matrix Raid is similar to Windows XP software RAID.

XP Raid creates a single volume out of multiple "standard" partitions.

Matrix RAID creates logical discs out of multiple partitions.

The only question is whether the partitions are "standard" partition recognizable by an OS when connected via a non-RAID controller.

Assuming a two disc Matrix RAID using RAID 1 & RAID 0, connecting a drive via a non-RAID controller could result in

A) A drive with no recognizable partitions
B) A drive with two recognizable partitions but no recongizable file systesm
C) A drive with two partitions one of which has a recognizable files system.

I am guessing the its going to be either A or C.
October 10, 2006 12:46:59 AM

Yes, I forgot, a RAID-1 on most RAID controllers does result in recognizable partitions when connected to a non-RAID controller. This is an exception to what I stated above.

However, it may not work that way on the Matrix RAID controller. If it does, I bet it only works that way if the RAID-1 is the first logical volume. If a RAID-0 is the first volume, you may not be able to see the RAID-1 at all.

When formerly RAID drives get connected to non-RAID controllers, I've seen a variety of results:

1. No partitions appear at all (entire drive appears to be unpartitioned space).
2. A partition exists, but it's an unknown type, or has no file system.
3. A partition with a recognizable file system exists, but the apparent partition and file system size is larger than the physical disk. Attempting to access files on the disk results in errors because LBA references point past the end of the drive.

However, I haven't taken drives from an Intel Matrix RAID controller to see what they look like when connected to a non-RAID controller, so I don't know which of these you'll see.

If the OP wants to do a combination of RAID-0 and RAID-1 on two drives, the Matrix RAID controller can certainly do that. But some research would be in order to determine what the RAID-1 looks like on another controller. Further, I was inferring from his original post that the unused space (not used by the RAID-0 logical volume) he wanted to be non-RAID. In other words, he wanted to take the 2x 320GB drives, create a 40GB RAID-0 (2x 20GB), and then use the remaining 300GB on each drive as separate drives, for a total of 600GB of available space. The Matrix controller can't do this. It could take the 300GB of extra space on each drive and create a 300GB RAID-1, but I think the OP didn't want to lose 300GB of space to redundancy for the second logical disk.
October 10, 2006 1:16:22 AM

Thanks again for all the replies. As soon as I get my new system, I'll play around with it and let you know what I find out.

It makes sense that in the configuration I suggest, even if it is possible, the non-RAID would not be recognized by any other controller after all. I wish it could work, but would be really surprise if it did.

Anyhow, I was thinking that if SomeJoe is correct and you gotta have some type of RAID on all partitions, then the solution might be RAID0 for the system, then JBOD for the rest. If that can be considered a legal configuration it would probably do for my needs, although it's not perfect.

BTW, any problems I should know about with JBOD? Apart from the fact that it probably also bundles the drives to a specific controller.
October 10, 2006 2:27:51 AM

Quote:
Anyhow, I was thinking that if SomeJoe is correct and you gotta have some type of RAID on all partitions, then the solution might be RAID0 for the system, then JBOD for the rest. If that can be considered a legal configuration it would probably do for my needs, although it's not perfect.


I thought about that. Some RAID controllers will let you create a single-drive JBOD to allow you to essentially use one physical disk. Alas, the Intel Matrix RAID controller does not have an option to create a JBOD. All logical disks must be RAID-0, RAID-1, RAID-5, or RAID-10. So unfortunately, that won't work.
October 10, 2006 4:24:11 PM

Your best chance of having a universally readable data is RAID 0/RAID 1 matrix.

RAID 1 is very handy anyway, as it ensures your data survives the death of a single hard drive.

All hard drive break down and die and while sometimes there are signs of impending doom and have time to move your data, other times the drive just stops working without warning.
October 11, 2006 5:15:50 PM

I might give that RAID0/1 combination a try. I wonder if the RAID1 partition (sorry, logical disk) will be seen by a non-RAID controller -- I doubt it, but I'll check. Too bad JBOD is not supported, kinda surprised by this I must say. In any event, I actually have automated backups to an external disk so RAID1 is not really a priority. But, I'll go ahead and play around with it nonetheless :) 

Thanks for all the advice, and if I find some elegant solution, I'll let you all know.

Cheers!
May 9, 2009 4:29:16 AM

I've spent the better part of today playing with this, and I have what I think is the perfect solution to all of this.
What works/what to do:
I have a gigabyte ep45-ud3p mobo. In the bios, enable raid. When it's booting, enter the raid utility. FIRST create your mirrored partitions. THEN create your striped partitions. Install windows on your striped partitions. Your striped partition (i know i am using that word technically wrong, but you get the idea) will be your boot disk, your c:/ etc. Your mirrored disk will show up as d:/. You can take one drive out, hook it up to another computer (even if it doesn't have raid), and the mirrored section will be recognized with no special effort. All the mirrored files are intact and accessible. The striped portion is, of course, gone.

What doesn't work/what not do: create the striped partition first. windows will not recognize the mirrored part on another machine, at least not with zero effort (i didn't find a way, but imagine there is one somehow). you can not (at least with my mobo) create more than two raid partitions. eg, you can't have striped swap partition, striped os/data/programs partition, and mirrored backup partition. it will force you to put all size not used in partition 0 into partition 1.

As far as the "raid 1 is not for backup" critics:
i will be using backup software to backup files from striped to mirrored. this way, if a file is corrupted on striped i have an old copy (or ten or twelve) on mirrored, and if either mirrored fails, i still have the other mirrored.

now wth stripe size i should have used, who knows. i maxed it out (128kb), since i watch tons of movies. all legally obtained, of course.
!