Hi,
I just installed a Dell R610 with PERC H700 512MB and BBU, 4x 146GB SAS Drives in RAID5.
Running ESXi 5.5 update 2 from 09-09-2014.
FW versions could be outdated (3 years old).
Write speed is POOR!! best case 10 MB/s.
Read speed is much better around 179 MB/s.
So probably the same issue as you are facing.
I tried to remove the VIB named lsiprovider but I cannot locate it on my ESXi nstallation
Maybe you have some other advice for me?
Also if there is anything I could test on my server for this matter that is no problem.
For now it is still being used as testenvironment.
Regards,