Powerstore and Disk.DiskMaxIOSize

Hi All,

I just wanted to share an experience in case anyone else has this issue.  First I will state that Dell does state that the Advanced ESXi setting on a host connected to Powerstore must be 1024.  In our case, prior to installing the Powerstore, we had another SAN (still connected in the environment) that wants this setting to be the default, 32767.  

We understood that 1024 was needed on the Powerstore so this was discussed with Dell engineering during the installation\project process and they recommended we keep the setting at 32767 until the migration was completed.  The problem is this caused major VM issues on a couple hosts running an older version of ESXi 6.7 as we were migrating these machines using Storage Vmotion.  Instead of just causing performance issues (which we could tolerate for a bit), it caused the VMs on these hosts to start throwing hard disk errors, "An error was detected on device \Device\Harddisk0\DR0 during a paging operation."  every couple of seconds.  Which ultimately made the VM unusable after a period of time (BSODs, failing services, etc.).

Based on this, we changed the Disk.DiskMaxIOSize to 1024 on all hosts and the errors ceased immediately.  The moral of the story is, no matter what you are told, set this to the lowest value required by your storage systems when you have multiple block level storage systems with different vendors or models (e.g. SAN 1 is fine with 32 MB but SAN 2 wants 1 MB IO size, set it to 1 MB on all hosts connected to SAN 2 even if SAN 1 is connected as well).