It's much easier via CLI for cDOT.
If you run this command:
SANCL1::> qos statistics volume characteristics show
You get output for all the volumes in the cluster, just look for Request size that's your IO size.
If you want to know the IO size for specific volume then use the following command:
SANCL1::> qos statistics volume characteristics show -volume v_dmz -vserver san01
Workload ID IOPS Throughput Request Size (IO Size) Read Concurrency
--------------- ------ -------- ---------------- ------------ ---- -----------
v_dmz 21451 6 3.00KB/s 512B 66% 0