Multi-threaded concurrent direct IO is slower on EXT filesystems versus raw block devices

Issue

• Multi-threaded IO utilizing O_DIRECT is slower on EXT2, EXT3, and EXT4 than it is on a block device
• An example workload such as a restore from a Sybase backup where Sybase is configured to use direct IO is much slower when using an EXT filesystem versus a raw block device
• The speed difference is as much as 200% slower on a filesystem versus raw block device