Cluster Hyper-V VMs slow

Hi,

I have a Hyper-V cluster with a CSV connected in ISCSI. Some of my VMs are very slow.

For example, I have some VMs (2008R2/2012R2) :  I/O -> 90Mb/s. Everything is Ok.

I have other Vms (2008R2/2012R2) : I/O -> 15Mb/s. Not ok.

The deduplication is activated everydays à 24AM.

Regards.