Add Support for Storage Spaces in virtual environment and as iSCSI target
Recently I looked at using an iSCSI target VHDX on a storage space volume in a hosted environment where I don’t have access to Hyper-V, so can’t create a dedup VHDX that the hypervisor uses.
The reasons I did this was three-fold.
1. I could create a VHDX using an iSCSI target to a Windows Server running Storage Spaces – hence a VHDX file on a Windows volume that I could dedup.
2. I now had a dynamic disk so for a space hungry application like DPM that requires overallocation for replica and recovery point volumes, I could create a large disk that would only grow when backup data was written.
3. The hosted environment only provided me with 2TB virtual disks as their largest size so Storage Spaces provided me a way to create a big Windows volume.
Unfortunately for me the solution was not stable and the support team have pointed out that Storage Spaces are not supported for iSCSI targets.
Dedup is one part of the solution I was hoping to use and would like to know if there are any supported scenarios or features being thought of where this type of solution could be implemented in a hosted virtual platform rather than only on a Hyper-V platform (as per the article outlined here http://blogs.technet.com/b/filecab/archive/2015/05/05/data-deduplication-in-windows-server-technical-preview-2.aspx)
Basically the real reason I’m creating the large iSCSI target is to allow me to grow the VHDX as a dynamic disk past the NTFS volume size. For the DPM application it’s replica and recovery point volumes require over-allocation of the data I’m backing up so there is wasted space there (backup of x file data must be x+1) which can be saved by using a dynamic disk as the DPM replica volume grows it doesn’t grow the dynamic disk until backup data is written to the volume. Also when backing up similar (BMR examples) targets the replica volumes for those targets will have very similar data so Deduplication on the NTFS volume will save me space and the VHDX actual size will be much smaller.