There's a bug when upgrading from ESX 3.0 to ESX 3.5. This bug has to do with Lunmasking. When performing the following mask command:
/adv/Disk/MaskLUNs =
vmhba2:1:19,20,36,37,38,39,40,41,48,49,50,89,90,91,92,93,94,95,96;vmhba2:2:19,20,36,37,38,39,40,41,48,49,50,89,90,91,92,93,94,95,96;vmhba4:1:19,20,36,37,38,39,40,41,48,49,50,89,90,91,92,93,94,95,96;vmhba4:2:19,20,36,37,38,39,40,41,48,49,50,89,90,91,92,93,94,95,96;"
This should mask all the luns, what you effectively get is:
/adv/Disk/MaskLUNs =
"vmhba2:1:19,20,36,37,38,39,40,41,48,49,50,89,90,91,92,93,94,95,96;vmhba2:2:19,20,36,37,38,39,40,41,48,49,50,89,90,91,92,93,94,9
This means there is a restriction in the amount of characters that can be set in 3.5 for masking luns.