Being able to specify a sector size larger than the default 512 bytes is another ASM feature of Oracle Databases 11g Release 2. Now, we can specify a sector size up to 4k. There is a new SECTOR_SIZE attribute while create the ASM disk group.
ASM Cluster File System (Oracle ACFS) does not support 4 KB sector drives.
There’s performance implications for Oracle ACFS when utilizing 4 KB sector disk drives in 512 sector emulation mode.
Posted by Charles Kim, Oracle ACE Director