The MirrorView Write Intent Log requires two 128MB LUNs, one for each SP. For whatever reason we could not get 128MB LUNs provisioned from a Storage Pool to show as available LUNs for the log-- but had no trouble using 128MB LUNs from a RAID Group. This may have just been that the LUN from the SP had some overhead taking it below the 128MB... but something I wanted to share.