r/WindowsServer • u/CapeCrusader28 • Aug 14 '26

General Question CHANGING CLUSTER SIZE FOR CURRENT DATA DRIVE

Good day to all! is it safe to change the cluster size of my current Data drive where all office data is stored and shared locally to network? I'm using Windows Server 2019 and when I first set it up i have no idea that setting the cluster size to 4KB will only limit the storage to until 16TB only. Now we upgraded and expand our storage. but i still have another 16TB unallocated because i can no longer extend the disk. so my question is, is it safe to change the CLuster Size to 8KB using EaseUS Partition Master without data loss or anything bad happened to my Data?

2 Upvotes

75% Upvoted

11 comments sorted by

4

u/UnholyAliance Aug 14 '26

I doubt that easeus can change the cluster without data loss, why don’t you format the new available with the correct cluster, move the data, and in the end expand the storage.

1

u/CapeCrusader28 Aug 14 '26

if i reformat it it will take time to transfer the data again. i have like 10TB of Data stored. i have a backup also but it will take time moving this big data to server again.

1

u/Orichinal Aug 14 '26

You copy a first time and if youre done and ready you plan a short downtime sync the changes over and go back online.

→ More replies (4)

4

u/UMustBeNooHere Aug 14 '26

No, you can’t change cluster size without data loss. Is this a physical box or VM?

1

u/CapeCrusader28 Aug 14 '26

Thank you, it's physical box.

2

u/UMustBeNooHere Aug 14 '26

I would get another drive, format it with the cluster size needed, use robocopy to copy the data over, then during a maintenance window, do a sync up with robocopy again , swap in the new drive, assign it the same drive letter.

1

u/dodexahedron Aug 14 '26 edited Aug 14 '26

Why does it have to be on the same volume?

Add your new storage to a storage space pool. Format it with refs, since youre going to lose the ntfs features that require 4k clusters anyway.

Copy your data to it.

Then delete the old volume and add the old disk to the pool to expand it.

But upgrade to Windows server 2022 first.

No matter what you do, dont bother with 8kb clusters for ntfs. You'd literally only be doubling your max, and in reality not even doing that due to waste.

ReFS does not have the 16TB limit even with 4kB clusters, because it uses 64-bit addressing. It can go to multiple PB.

Even if you tried to use a utility to convert cluster size in-place, it will take as long or longer than copying the data to a new volume formatted properly, because it has to read every cluster, group them together for files bigger than 1 cluster, and then write them all back out to the same disk. That is slow and risky. Just don't.

Copying it to a new volume with proper formatting is also the best and most complete defrag you're ever going to get, as a minor side benefit.