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Disk size changes after installing windows server 2008

Dear Experts,

Our server has 16 bays,

14 Bay = 300 GB (Date), RAID 50, ~3.3 TB
2 Bay = 146 GB (System) Mirror, 140 GB

Windows 2008 installation is on System drive.  After installation complete, everything changes. system drive takes some of Data drive as you see from the attached image, and Data drive get divided in to two partition, I can’t even separate them.

Why this happens?
3 Solutions
Paul HuxhamCommented:
Hi uknet80

I notice your data disk is "disk 0" and you system disk is "disk 1".  This is not best practice as the system disk would normally be disk 0.  In your RAID array the two 146GB system disks should be in the first two drive bays (normally 0 and 1, or 1 and 2).  This should cause the system disk to be "disk 0" and will prevent the OS from taking part of your data drive.

If that doesn't work, delete the data drive from thew RAID controller, install the OS on the system disk, then create the data drive on the RAID controller after the OS is installed.

Mohammed KhawajaManager - Infrastructure:  Information TechnologyCommented:
If you want contiguous disk (one big 3 TB drive) then right click on DISK 0 and convert it to GPT.  If you have difficulty then refer to article below.  With respect to DISK 0 and DISK 1, this is not an issue as during OS install, you can select which disk you would like to have for system drive.
Windows creates a small 100MB partition for it's boot loader. This is installed on the first bootable drive it finds, which in your case is the large array.

To avoid this, make sure your large array isn't set to "bootable" (should be possible via the BIOS / RAID configuration utility), or have the array removed while you are installing the OS. Then install the OS again.

Another way of avoiding this, provided you don't need to encrypt your OS drive, is to prevent the creation of the small 100MB partition during the installation. When you get to the point where you can select the disk and partition to install to, first delete all the partitions. Then press Shift+F10. This gets you a CMD prompt. Then enter the following commands:

select disk 1
create partition primary

After that press "refresh", and then select the partition you just created to install the OS to.

Once you have Windows setup, you can open diskmanagement and make sure your big array is set to GPT, as has already been mentioned above.
System reserve partition by default created on Disk 0. When you are installing OS , first it searches the Disk 0 and if found then it will create the system partition over Disk 0 though you have selected the Os drive as disk 1.

In this case  if you are installing Os on disk 1, then you can build raid 50 after installing the OS.So that your system reserve partition will be created on Disk 1. As long as it finds the Disk 0 then it creates the system reserve partition on disk 0.
uknet80Author Commented:
thanks to all
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