latency on MD3420

Hello

I’m working with a Hyper-V Cluster of 2 R630 and a MD3420 (RAID 5 of 24 HDD SAS 10k 1To).

This cluster hosts especially 1 Exchange 2010 server (700 Mbx), 2 Exchange 2013 (30mbx and 100mbx).

I’m facing some latency problems in my Exchange servers, especially during VEEAM Replication job.

While troubleshooting I have some questions:

1. Is the sizing of my storage OK ?
2. My MD3420 has only one LUN,  I would like to know if it is normal that the iops of the disk_pool are the double of the iops of the DATA virtual disk (there is no other virtual disk, excepted the disk dedicated to the Quorum)