Dynamic Disk shows two slices of "Unallocated Space"

Posted on 2014-03-11
Last Modified: 2014-03-27
Hello all,

I have an issue with a dynamic disk showing two slices of "allocated space". This is how I got to it:

1) Created Partition 1 and Partition 2 on DISK1
2) Converted Disk 1 to Dynamic
3) Formatted both partition with 64K cluster size (to support for future upgrades of partitions to over 16TB without having to re-format).
4) Added more disks to the RAID array and extended the array and the logical drive.
5) Refreshed disk management and I see two slices of "Unallocated Space" one of 127GB and the other 8TB.
6) Trying to extend partition 1 or 2 over 127GB and it fails. Its as if the extra space is not seen. This is where I am stuck.

Any help would be greatly appreciated for this.

Info of cluster sizes:

Hardware/Software Info:
Windows 2008 R2 on a HP ProLiant DL380p Gen8.
HP D6000 Disk Enclosure

Question by:Ars_Technica

Expert Comment

by:Shahnawaz Ahmed
ID: 39921391
Did you try diskpart to extend the drive/partition?

Author Comment

ID: 39921398
Yes I did.

Same error as with the GUI when trying to go over 128GB : Not enough space.

Expert Comment

by:Shahnawaz Ahmed
ID: 39921411
Its it will give you the error if you go over 128 GB. If you expand 127 GB it suppose to allow you. Because there is a 128 GB space chunk residing in between and you can not skip without using it.

Expert Comment

by:Shahnawaz Ahmed
ID: 39921421
Suppose if you want to increase 200 GB total then go for 128.98 GB first then 72 GB from another chunk of data storage.

Author Comment

ID: 39921447
Hello and thank you for the responses.

I have created another partition of 128.98 and tried to extend that drive as suggested and same issue. I tried with the GUI and using diskpart.

Note the free space reported by diskpart for disk 1: 0B (the extra slice of 8 TB not showing up).
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Expert Comment

by:Shahnawaz Ahmed
ID: 39921467
I m not sure if there is any limit of storage we can extend via diskpart. Can you try to extend by 200 GB once???

Expert Comment

by:Shahnawaz Ahmed
ID: 39921514

There is limitation of Disk Size in windows which is 2 TB. So below 2 TB you can extend but not more than that a single partition.

Author Comment

ID: 39921563
Hello Shahnawaz,

As far as I know, when you do not specify the size, it uses the maximum size available. And as for the 2TB limit, it should not affect me as I am using a GPT disk (non MBR) on a dynamic disk.

My other partitions are 6TB and 12TB.

When using 4KB clusters for my Partition 1 and 2, I did not see this issue. I had no choice but to format the partition 1 and 2 using 64K clusters because these partitions will be upgraded to over 16 TB in the future. The default 4KB clusters allow a maximum size of 16TB.

I have already extended a <2TB partition to over 8 TB without any issues provided that the space is available.

As for your suggestion extending the drive by 200GB at once it fails with the same issue.

I am wondering if this issue has something to do with 64K cluster sizes. I did not have this issue with 4K cluster sizes.
LVL 55

Accepted Solution

andyalder earned 250 total points
ID: 39926862
Why on earth are you using dynamic disks in this day and age? 10 years ago maybe because that was the only way to break the 2TB barrier by sticking lots of sub-2TB slices together but now that there's GPT there's really no excuse for dynamic disks any more.

See for example, dynamic disks are supported but best practice is to use basic disks.

As far as extending basic disks on MBR is concerned it works fine but it only extends into free space immediately after the partition, so if you have E: and F: on a single logical disk on the RAID controller and extend that logical disk you can only extend F: and not E:. You can create two logical disks on a single array using the ACU, then when you add more physical disks you can extend either or both of them using the ACU and then expand E: and F:.

You can't expand C: at least not live under Windows but I don't think you're trying to do that. C: is limited to 2 TiB anyway since ProLiants can't currently boot GPT disks as they do not have UEFI.
LVL 34

Assisted Solution

by:Seth Simmons
Seth Simmons earned 250 total points
ID: 39928310
that was a thought i had also
is there a specific reason why dynamic disks are being used?
a gpt basic disk is sufficient
i was reading posts where some have had weird issues with dynamic disks and after backing up data, converting to basic and restoring their data they didn't experience the same partition issues

Author Comment

ID: 39959741
Hello all,

Thank you so much for your responses. I have abandoned dynamic disks and instead creating two arrays with basic GPT disks.  It it to note that I was not able to reproduce the problem after re-building the system from scratch several times as mentioned above and using the exact same procedure.

I was using dynamic disks because I had requirements of using a single array of disks that would start with a certain amount of TB and scale upto 200 TB, and contain two partitions (windows drives) that one would be double the size of the other. But this was changed recently.

Thank you all for your insights on this issue.

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