RHEL 7.4 ext4 I/O permance issue compared to RHEL 5.11 ext3

What problem/issue/behavior are you having trouble with?

Below script is being used to do a disk performance test:

for i in {1..50}
do
sleep 2
sync
echo -e $i" \c"
dd if=/dev/zero of=$PWD/testfile oflag=direct bs=1G count=1 2>\&1 |\
awk -F, '{print $3}'|grep -v "^$"
rm -f testfile
done

This scripts shows a throughput of 1.4GB/s on ext3 filesystem at RHEL 5.11.

Running the same scripts on RHEL7.4 can reach on ext4 700MB/s and on ext3 550MB/s.
At first on xfs speeds of 1.2GB/s could be reached, but since a few days the speed drops to 880 MB/s and we have not found a way to get it fixed.

A Red Hat case has all ready been created, but I hope one of the Forum Members might know a solution.

Both VM's ran at the same VMware Datacenter during testing.