Provide block layer support for the kernel. Disable this option to remove the block layer support from the kernel. This may be useful for embedded devices. If this option is disabled: - block device files will become unusable - some filesystems (such as ext3) will become unavailable. Also, SCSI character devices and USB storage will be disabled since they make use of various block layer definitions and facilities. Say Y here unless you know you really don't want to mount disks and suchlike.
Enable block devices or files of size 2TB and larger. This option is required to support the full capacity of large (2TB+) block devices, including RAID, disk, Network Block Device, Logical Volume Manager (LVM) and loopback. This option also enables support for single files larger than 2TB. The ext4 filesystem requires that this feature be enabled in order to support filesystems that have the huge_file feature enabled. Otherwise, it will refuse to mount in the read-write mode any filesystems that use the huge_file feature, which is enabled by default by mke2fs.ext4. The GFS2 filesystem also requires this feature. If unsure, say Y.
Saying Y here will enable generic SG (SCSI generic) v4 support for any block device. Unlike SG v3 (aka block/scsi_ioctl.c drivers/scsi/sg.c), SG v4 can handle complicated SCSI commands: tagged variable length cdbs with bidirectional data transfers and generic request/response protocols (e.g. Task Management Functions and SMP in Serial Attached SCSI). This option is required by recent UDEV versions to properly access device serial numbers, etc. If unsure, say Y.
Some storage devices allow extra information to be stored/retrieved to help protect the data. The block layer data integrity option provides hooks which can be used by filesystems to ensure better data integrity. Say yes here if you have a storage device that provides the T10/SCSI Data Integrity Field or the T13/ATA External Path Protection. If in doubt, say N.
Block layer bio throttling support. It can be used to limit the IO rate to a device. IO rate policies are per cgroup and one needs to mount and use blkio cgroup controller for creating cgroups and specifying per device IO rate policies. See Documentation/cgroups/blkio-controller.txt for more information.