Description of problem:

In Sequential FIO tests being executed on RHHI with VDO(+/-), with deduplication level in range(0,25,50,100) and iodepth in range (1,4,8,16), it is seen that particularly the sequential throughput on SSDs and RAID 6 are less with VDO.

RAID 6 throughput dropped down to 70% approx w.r.t Non-VDO RHHI
SSD throughput dropped down to 80% approx w.r.t Non-VDO RHHI 


FIO Command used:
fio --name=sequentialread --ioengine=sync --rw=read  --bs=128k --directory="{{ fio_test_directory }}" --filename_format=f.\$jobnum.\$filenum --filesize=16g --size=16g --numjobs=4

Version-Release number of selected component (if applicable):

gluster version:
glusterfs-3.8.4-54.15.el7rhgs.x86_64.rpm                                           
glusterfs-api-3.8.4-54.15.el7rhgs.x86_64.rpm                                          
glusterfs-api-devel-3.8.4-54.15.el7rhgs.x86_64.rpm                                  
glusterfs-cli-3.8.4-54.15.el7rhgs.x86_64.rpm                                        
glusterfs-client-xlators-3.8.4-54.15.el7rhgs.x86_64.rpm                             
glusterfs-devel-3.8.4-54.15.el7rhgs.x86_64.rpm                                      
glusterfs-events-3.8.4-54.15.el7rhgs.x86_64.rpm                                     
glusterfs-fuse-3.8.4-54.15.el7rhgs.x86_64.rpm                                       
glusterfs-ganesha-3.8.4-54.15.el7rhgs.x86_64.rpm                                      
glusterfs-geo-replication-3.8.4-54.15.el7rhgs.x86_64.rpm                              
glusterfs-libs-3.8.4-54.15.el7rhgs.x86_64.rpm                                         
glusterfs-rdma-3.8.4-54.15.el7rhgs.x86_64.rpm                                         
glusterfs-resource-agents-3.8.4-54.15.el7rhgs.noarch.rpm                            glusterfs-server-3.8.4-54.15.el7rhgs.x86_64.rpm          


rhv version:
rhv-4.2.5

How reproducible:


Steps to Reproduce:
1. Setup RHHI with and without VDO
2. Provision a vm and add (RAID6/SSD) storage disk to VM (Virtio-blk,thin-provisioned)
3. Create xfs filesystem over the block device added to the VM and mount it.
4. Install Fio, in the command above , replace "{{ fio_test_directory }}" with the mountpoint and run the fio test.

Actual results:


Expected results:


Additional info:



Result sheet:
https://docs.google.com/spreadsheets/d/1OjQ5gaYj9Vo2SwV0gmZN_SmdBanNCqQmxVwpLkuurdg/edit?usp=sharing