We have a new Synology RS3412RPxs that offers iSCSI targets to three Windows 2008 R2 boxes and NFS to one OpenBSD 5.0 box.
Logging into the RS3412 with ssh and reading/writing both small files and 6GB files using dd and various blocksizes show great disk I/O performance.
Using dd or iometer on the iSCSI/NFS clients, we reach up to 20Mbps (That's not a typo. Twenty Mbps). We were kinda hoping to make better use of the multiple Gbit NICs in the Synology.
I've verified switch and NIC port configuration is set to gigabit, not auto-negotiate. We've tried with and without Jumboframes with no difference. I've verified with ping that the MTU is currently 9000. Two firmware upgrades have been deployed.
I am going to try direct link between the iSCSI target and initiator to rule out switch problems, but what are my other options?
If I break out wireshark/tcpdump, what do I look for?