Low performance on one of the VNX 5200 controllers

are you sure you dont have a multi-pathing problem with the config on your host ?

What is the host operating system?  Do you have PowerPath installed?

Yes, I forgot to write. If the path selection policy is set to fixed, the problem disappears.The image of ESXi 6.5 is used  from Dell, what can be wrong with round-robin?

I'd recommend that you review the Best Practices for VNX - when you create a LUN in a Pool, the LUN is assigned an Allocated SP owner and then the Default and Current SP Owner. If you trespass the LUN from the Allocated SP owner (say SPB) then the performance of the LUN will be impacted. Best Practice for VNX (VNX1 and VNX2) specifically states that if you need to move a LUN to the peer SP, you must use a LUN move operation - move the LUN to a new LUN that is created on the peer SP first.

https://support.emc.com/docu42660_VNX2_Unified_Best_Practices_for_Performance_-_Applied_Best_Practices_Guide.pdf?language=en_US

glen

Looking a the VNX McX white paper with the explanation of ALUA wouldnt hurt

I created the LUN on controller A and the formatting on the ESXi was completed with an error. I also noticed that the I / O module has the status Removed.How can this be remedied?

If you sure that there is supposed to be a IO Module in the A0/A1/A3/A4 slots then you'll need to contact support. In the VNX, the IO modules are mirrored on SPA and SPB - check that the IO modules on SPB match what you have in SPA.

glen