I strongly suggest you open a support case on any performance related issues.  However, with ESXi especially when I see low I/O + latency,  the first thing I usually find is that DelayedACK is enabled.  Sometimes, Large Receive Offload (LRO) can do this as well.   Another common issue is not optimizing MPIO.  I.e. not using Round Robin with 3 IOs per path vs. default of 1000 IOs.  Or if you have an Enterprise or Enteprise+ license installing Dell EQL MEM.   Also sharing multiple VMDKs with a single Virtual SCSI adapter inside each VM is another cause of latency.   Each VM can have up to four (4) Virtual SCSI adapters.  With only one adapter, only one VMDK (Disk) can be active at any one time.  So an I/O operation on the "C:" drive will block your SQL drives.    This link has a PDF that will show you how to correct common mis-configurations with ESXi + EQL.  en.community.dell.com/.../20434601.aspx HOWEVER.  If you find delayed ACK is enabled the process described there won't likely be enough to fix current connections.   With the node in maint mode.  Remove the EQL discovery address, remove the "Static Discovery" entries for EQL volumes.   Then reboot node.   Add Discovery address back in but do NOT rescan yet.  Verify that login_timeout is at 60, and DelayedACK is disabled.   Then do the rescan.   Regards, 
Hi,   I have a Dell PS4100xv with 12x 600 GB 15K SAS drives configured at RAID 6.   Three (3) R420 servers are connected via 2x Power Connect 6224 (stacked).   I'm running ESXi 5.1 U1 with a mix of SQL VMs, File servers and Proxy servers.   What are acceptable values for a healthy EQL in terms of latency, disk queue, IOPs and etc?   Just recently, I transferred a VM to the PS4100XV. The VM has very sluggish behavior when operating from the Dell EQL. It's SQL Server. Got a lot of users complaining on the sluggish behavior.   I need to determine, if I have a problem on my PS4100xv in terms of performance before I start troubleshooting the VMs and ESXi hosts.     These are the readings taken from SAN HQ for the last eight hours.     If, I got this right this my own analysis           Disk Queue Depth: zero (0), the   graph show its flat at zero. Average READ IOP: 625 Average WRITE   IOPS: 117 Total Average IOPs 742     Average READ   Latency 30 ms (20 ms to 40   ms) Average Write   Latency 13 ms (straight   line @ 13 ms) Weighted Average 28 ms     Average IO Rate   Reads 26.41 MB/sec Average IO Rate   Write 2.26 MB/sec Total 28.67 MB/sec     Average IO size   READ 43.30 KB Average IO size   WRITE 19.91 KB Weighted Average 39.62 KB   There are no retransmit packets and network utilization is at 3% only.   Would really appreciate any inputs and recommendations.  What are acceptable values for a healthy EQL in terms of latency, IOPs, disk queue and etc?     Thanks, Paul  
DELL PS4100xv and SAN HQ acceptable Disk performance