Question about RAID and dynamic disks

[segil]

Hello everybody,

I've got a question about extending my RAID configuration. We have a Windows 2000 DC on a Compaq Proliant ML350 server with a Smart Array 431 controller and three 18 GB disks in a RAID 5 config.
This array consists of one logical drive of 36 GB. This drive is formatted as a Windows 2000 dynamic disk and divided into two volumes, the w2k system volume and a data volume. Both volumes are running out of space and I want to add another drive to the RAID, so I've purchased a 36 GB drive (18 GB isn't sold anymore).
Compaq says that I can add this drive online using ACU and the array will be rebuild. After that, I can extend the dynamic volumes using the free space and that's it. Is it that easy?
Microsoft says that a system volume can't be extended. Is that true? And what about the remaining unallocated 18 GB on my new 36 GB drive? Can I use that in some way?

So my questions:

1. Is it possible to extend a system volume on a dynamic disk, containing the Windows 2000 server installation?

2. Can I use the unallocated 18 GB space on my 36 GB drive or is it just wasted?

3. Can this all be done while the DC is running, or does it need to be rebooted a few times?

Thanks a lot for your help!

 

[Jpoandl]

My suggestion, for future reference, is that you do NOT use dynamic disks if you have hardware RAID. Dynamic disks are meant for Software based RAID sets. Dynamic disks give you the ability to extend you raid set.

However, dynamic disks running on hardware RAID can cause problems when you try to extend the volume. I know, I ran into this issue. Dynamic disks may not be supported on 3rd party utilities to extend partitions (like server magic, volume magic). So, you are forced to rely on Windows based volume extention.

Pre-Requisites for Disk Expansion

Before disk expansion can take place, it is important to meet these minimum requirements:

· Make sure that a current full backup of the data volume is available
· Upgrade the RAID Array Controller firmware (See HP web for more information:

http://wwss1pro.compaq.com/support/...=29&source=EM000915_CW01.xml&dt=3&docid=2996)

· If possible, upgrade the hard disk firmware
· The data volume must be a BASIC disk. Dynamic disks are not supported using this procedure
· Windows OS must be either Windows 2000 SP3 (or greater) or Windows 2003

Note: Microsoft Recommendation regarding Dynamic Disks: If you do not need software based spanned volumes, striped volumes, mirrored volumes, or RAID-5 sets, it is best to use basic disks


More information can be found here:

BEST PRACTICES FOR USING DYNAMIC DISKS:

http://support.microsoft.com/?kbid=329707

There is no reason to run dynamic disks when you have hardware RAID. However, it sounds like you are already in this situation. So, we might as well just move on...

If you add the 36gb to the RAID set, you will lose the extry 18Gb's. There is nothing you can do about this...but at least, you will gain the additional disk space in your array.

This is a 4 step process...

1) insert the new disk physically to the server (no reboot)
2) Run the ACU and Expand the RAID Array with the new disk (no reboot)

Now when you go into the ACU, you will see available disk space. However, you need to add the disk space to each volume through the ACU. This is where you allocate the new disk space to each partition.

3) Run the ACU and Extend the volume (no reboot) with the proper additional disk space to each volume. (I've never tried to extend a system partition...you may want to call HP to find out about the limitations (if any) with your RAID card.


Now your additional disk space has been allocated as far as your RAID array is concered. Howerver, the OS will still "see" the original size. You will have to use a program to grow the partition so the OS realizes the additional space.

4) Use MS tool called DISKPART to grow the data volume:

http://support.microsoft.com/default.aspx?kbid=325590

Once diskpart is complete, you are done.

Hope this helps..


Joseph L. Poandl
MCSE 2003

If your company is in need of experts to examine technical problems/solutions, please check out

http://www.NJCOMPUTERNETWORKS.com

(Sales@njcomputernetworks.com)

 

[segil]

Hello Joseph,

thanks for your great reply! I will try to add some more information.

Unfortunately this server was already installed in this way by a former sysadmin, I don't know why he did it like this.

To make everything clear... the array consists of ONE big logical volume and that volume is used in Windows for two partitions (C-drive and D-drive). These partitions are dynamic, so I call them 'volumes'. So my idea was to add the fourth disk, create a second logical volume in the array and use MS diskmanagement to use this new logical volume to add more free space to the existing two dynamic partitions. But MS says that in this way you can't add more free space to a dynamic drive that has the Windows 2000 installation (the system partition). Do you know if that's true?
The reason why I want to extend my C-drive is because that lovely former sysadmin created a 3 GB C-drive! And now I have about 400-500 mb free. Not much huh?! So that's way I want to extend my C-drive.
I would like to backup the Windows installation, but it's also a DC so I'm not sure how to successfully restore it when necessary.

Thanks for your help.

 

[figmatalan]

You shouldnt worry too much about that much space on your C drive. The C drive should be restricted to the OS and a few tools. I've seen installations with a 2Gb C drive with 200-300Mb free but the server is completely OK so really dont stress.

 

[Jpoandl]

The only way that I have been able to successfully grow a C: drive was to use third party software. (Last time I tried was about 2 years ago...the process worked very nicely though. But I had to buy Server Magic to do it.)

The new "server magic" product is called Volume Manager made by Symantec.

http://sea.symantec.com/content/product.cfm?productid=7

However, I see that on their website this warning: Note: Symantec VolumeManager supports basic disks only in Windows 2000. Dynamic disks (LDM) are not supported at this time.


Your only option may be to backup, resize partitions, and restore.

Joseph L. Poandl
MCSE 2003

If your company is in need of experts to examine technical problems/solutions, please check out

http://www.NJCOMPUTERNETWORKS.com

(Sales@njcomputernetworks.com)

 

[segil]

Thanks for your reply!

I know that normally 3 gb is enough for a Windows installation, but I've had some situations that required more local diskspace... for example, when the DC is also a print server and the spooler folder is located on the C drive, then a big print job (e.g. printing 50 copies of a 40 mb Word document) can really take up all the free space on the C drive! Or when a Arcserve installation is located on the C drive and the LOG/database folders becomes bigger and bigger... believe me, you can run into strange situations!

I'm a bit hesitant about backing up data and restoring on a DC. My nightmare is that AD will have some serious problems after that.

I'll let you know if my idea works or not. Thanks a lot for your information!

 

[figmatalan]

I've worked in several global organisations with thousands of servers worldwide and the policy they all adopted was to install the OS with a few tools on C and any applications which required any disk space went on a D drive.

This included printer spools, AD direcories, backup programs, Office products, etc, etc.

I've adopted this in my home installations and it's works well as you can trash the C drive and when you come to re-install any apps on the D drive, etc, most of them pick up the settings from the old installation which saves some time.

I'd look at moving your print spool folders to D along with Arcserve and AD too.

 

[segil]

I've implemented that policy also, but my predecessor didn't. Once Arcserve is installed, it's not possible to move these directories to another location, without reinstalling the program. The print spooler is now located on the D drive, together with the data files. Since this drive has user quotas enabled, the print spooler can't exceed the users quota!

AD is still located on the C drive. Do you think it can grow much in size? Is it easy to move this database, without corrupting AD?

 

[figmatalan]

Unless you make a lot of AD changes the size wont change much. If you have another server that AD is replicated to then theoretically you can transfer any FSMO roles off this server and force a directory replication so any changes made on it are sent out.

Once you've done this you can take it out of the domain/forest and reconfigure AD to another drive then add it back in and transfer any roles back over to it and AD should replicate back.

I've done it on a small system and it worked OK.

 

[segil]

Hello,

thanks for your reply. It's also possible to move the AD databases using the following MS article:

http://support.microsoft.com/default.aspx?scid=kb;en-us;257420&Product=win2000

Another question: I'm thinking about creating an extra partition in Windows for the AD databases and also for the Windows paging file. Is this a smart thing to do?