Recently we brought a new Netapp3240 with SAS disks.so i have carved out some 50 LUNs from the raid-DP set and assigned it to a windows host2008 x64 using microsoft MPIO .During carving these luns while creation of qtree i didnt select the NTFS security style instead opted for UNIX security style .Now does that really make any difference by selecting this luns with wrong security style as those volumes are formated using NTFS filesystem .If what ever i have done is wrong then changing it now to NTFS security style will it corrupt the data.
You need to be careful differentiating between volumes and qtrees and luns. The security style is set on the volume/qtree. You create a lun at that level as well. The luns are presented to the windows box, and are formatted with NTFS - the volume/qtree is NOT formatted with NTFS.
The security style of the volume/qtree won't affect the luns that live there; it only manages file permissions via NFS and CIFS. The lun file permissions are managed by the filesystem on that lun and the host it is presented to.
Changing security style never affects data; it will affect volume/qtree level file ACLs, which may make data inaccessible (via CIFS/NFS), but data itself is unaffected. In your case, if all that you have under these volumes are luns, then changing the security style won't have any effect.