What NTFS allocation unit size is best for OLTP databases? SQL executables, log files, data files are all located on separate channels. Was thinking that OS and SQL executables should be on the default for the disk (4KB). Data and log files on drives that have an 8KB block size (thinking that OLTP servers do a lot of random IO in 8KB blocks). Or, should we use 4KB or 64KB block sizes for data and log drives? What does SQL Server like best for the data and log drives?