There is no risk involved if you want to change host port mode from FC to iSCSI. This is just related to which protocol and interface you want to use for data transfer. Important point to keep this in mind that this is offline process.
Regarding your data and filesystem level partitions or MSA vdisk and volumes information all reside in drive metadata so all is safe.
Hope this helps!
Regards
Subhajit
I am an HPE employee
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