I have recently installed a new VNXe1600 1Gbps ISCSI SAN. I have 4 active connection going into an HP 1900 switch. I have set all MTU values across the board to 9000. I also disabled Delayed ack and set the default Round Robin Policy to 1. We are using the Software ISCSI adapter. I have logged a call with EMC and they recon the SAN performing okay.
I'm getting performance problems with our SAP server. Sometimes it gets so bad that I see a message that the Database disconnected. When looking at ESXTOP all seems okay except for the storage. Where I'm seeing the below. This happens regularly about every 2-5 minutes. I can also reproduce this by performing a simply query.
Latency is around 5-10 ms on read and write. Every blog I'm reading points to changing the q depth length, but I can't find any recommendations from EMC.
Should the q depth be changed? If so, how and to what?
Is the SAP VM generating to many IOPS and I need to look at SSD cache?