Windows RAID question.

Tom · May 02, 2007, 10:23:21 PM

I'm mostly sure the answer to the following question is no, but I want to make sure.

Can you install windows (ie: the os itself) to a "Dynamic Disk"? I know that sort of thing is possible*, but I don't know if its possible for windows.

*) I had linux installed on a 2 drive software raid, /(raid0) /home(raid1) swap(raid0) and /boot(raid1).

Melbosa · May 02, 2007, 10:29:46 PM

Explain Dynamic Disk better please.

Lazybones · May 02, 2007, 10:43:48 PM

You can make the disk that hosts the system partition a dynamic disk, but you can't install the System partition it self on a Windows Software raid because there is no mechanism to create it before the OS is installed.

Tom · May 02, 2007, 10:49:02 PM

QuoteExplain Dynamic Disk better please.

A Windows Dynamic Disk allows greater flexibility in resizing, handles raid like features, but of course comes with its own partition format.

QuoteYou can make the disk that hosts the system partition a dynamic disk, but you can't install the System partition it self on a Windows Software raid because there is no mechanism to create it before the OS is installed.

Now would it be possible to make the system partition part of a Raid1 Dynamic Volume after its installed?

Lazybones · May 02, 2007, 10:52:05 PM

Quote from: Tom on May 02, 2007, 10:49:02 PM
QuoteYou can make the disk that hosts the system partition a dynamic disk, but you can't install the System partition it self on a Windows Software raid because there is no mechanism to create it before the OS is installed.
Now would it be possible to make the system partition part of a Raid1 Dynamic Volume after its installed?

I don't know, RAID 1 would be the only one that it MIGHT let you use since you should be able to create a mirror without destroying data. All other RAID levels require the parity set to be in place before data is written.

Tom · May 02, 2007, 11:00:27 PM

I'll have to play with it then. Or I can take some actual time and figure out which of the 160s I have is the one that had the dead sectors (it doesn't now, but more could show up) and not put it in the machine I'm building for my dad...

I was thinking that if I couldn't figure out which one it was, I'd just stick both in the box and mirror them. We shall see.

Melbosa · May 02, 2007, 11:23:44 PM

That is what I thought you meant. My RAID 5 can dynamically increase, and the only way to expand the partition in windows is to use Dynamic Disks and then set it up to span (if I use a new LUN that is).

Some good articles:
http://support.microsoft.com/kb/816307
http://support.microsoft.com/kb/323432 - This one has your answer I believe

Easy way to test this is VMware server. Quick and easy, and doesn't require you to reinstall your comp.

Tom · May 02, 2007, 11:33:31 PM

Ahh, very cool. I'll have to test that out. Thanks.

QuoteMy RAID 5 can dynamically increase

So can mine

XFS even does online expansion. Last week when I had the drive failure, it stayed online in degrade mode, and I didn't even notice any slowdown (over my punny 100mb/s lan). And once I added the new drive, it rebuilt itself online, and I didn't have to touch a thing. Its all rather slick.

Cova · May 03, 2007, 10:54:44 AM

Melbosa: you can expand basic partitions on your server without setting up new LUNs and without using dynamic disks. Use diskpart just like we do at work for resized VMWare disks / EVA LUNs.

Tom: It used to be possible to put the windows system drive on software raid before they had Dynamic Disks (eg. the NT4 days). I haven't tried since then thanks to hardware raid - but MS usually doesn't take features like that away.

Keep in mind that when booting from a software RAID partition that the MBR sector is usually NOT mirrored. So depending which drive fails you may need a boot floppy to get back into windows. I can get around that with grub and putting a bootable MBR on both drives - I dunno if the MS bootloader can do that, it couldn't back in the NT4 days. We always just kept a emergency boot disk (now called an ASR disk) around.

Melbosa · May 03, 2007, 01:34:46 PM

Quote from: Cova on May 03, 2007, 10:54:44 AM
Melbosa: you can expand basic partitions on your server without setting up new LUNs and without using dynamic disks. Use diskpart just like we do at work for resized VMWare disks / EVA LUNs.

That is why I said:

Quote from: Melbosa(if I use a new LUN that is).

Cova · May 03, 2007, 02:56:35 PM

Quote from: Melbosa on May 03, 2007, 01:34:46 PM
Quote from: Cova on May 03, 2007, 10:54:44 AM
Melbosa: you can expand basic partitions on your server without setting up new LUNs and without using dynamic disks. Use diskpart just like we do at work for resized VMWare disks / EVA LUNs.

That is why I said:
Quote from: Melbosa(if I use a new LUN that is).

And I specifically left that part out when I corrected you. If you create a new LUN, then windows will see the array as two separate physical disks. At that point your only option to turn them into 1 "drive-letter" is to use dynamic disks and span them together.

When you are dynamically expanding an existing LUN, such as when doing something like your quote of "My RAID 5 can dynamically increase" implies - then you do NOT have a new LUN, and you want to use diskpart to extend a basic partition - no dynamic disks, or software raid, or anything else required.