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parameter	description	required
id	data volume id	true
size	new size in gigabytes (if custom disk offering)	false
diskofferingid	disk offering to migrate volume to (if not currently custom offering)	false
shrinkok	required boolean value, signing off confirmation on volume shrink (dangerous if admin doesn't know what they're doing)	false

XenServer

XS only support volume size grow

XS doesn't support volume size shrink