Terrible performance of RAID10 on 256GB Dell PE820 KVM host

I have a 4-way Dell PE820 with 256GB of memory that primarily runs CPU intensive KVM guests. The system has a PERC 710 controller with a battery attached. I recently added 8 Seagate ST600MM0026 SAS 600 GB drives and created the following hardware RAID 10

• 64KB stripe size
• write through enabled
• disk cache enabled
• read ahead enabled

The RAID synced just fine and the RHEL6.5 (2.6.32-431.11.2.el6.x86_64) host sees the device just fine. I created a partition with parted

Model: DELL PERC H710 (scsi)
Disk /dev/sde: 2398GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system  Name  Flags
 1      1049kB  2398GB  2398GB  ext4         data

and formatted it ext4

mkfs.ext4 -b 4096 -E stride=16,stripe-width=64 /dev/sde1

I then mounted it without any special flags (mount /dev/sde1 /mnt/new)

The problem is that just about any IO I try is brutally slow or just hangs. For example, I can't even get bonnie++ to finish one test, it just hangs on 'Writing Intelligently' step. Watching things like iostat and vmstat show virtually no activity on the device or other devices on the system for that matter.

I installed tuned and enabled the enterprise-storage profile, but that did not seem to help.

If I do cude tests like 'badblocks /dev/sde' and watch iostat, I see reasonable values like:

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
sde            8134.50   1041216.00         0.00   10412160          0

If I do a simple dd test like 'dd if=/dev/zero of=bogusfile count=5M',

5242880+0 records in
5242880+0 records out
2684354560 bytes (2.7 GB) copied, 27.4337 s, 97.8 MB/s

I see values like this from iostat

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
sde             914.20         0.80    365319.20          8    3653192

If I then attempt to copy this bogusfile 'time cp bogusfile bogusfile2' , it takes a long time!

# time cp bogusfile bogusfile2

real    2m37.567s
user    0m0.032s
sys 2m36.510s

Any suggestions on what I have setup incorrectly? Thank you