Installation guide

File System tools
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This is the catch-all for "legacy" devices which don't appear to provide I/O hints. As such, by default
all partitions will be aligned on a 1MB boundary.
Note
Red Hat Enterprise Linux 6 cannot distinguish between devices that don't provide I/O hints
and those that do so with alignment_offset=0 and optimal_io_size=0. Such a device
might be a single SAS 4K device; as such, at worst 1MB of space is lost at the start of the disk.
File System tools
The different mkfs.filesystem utilities have also been enhanced to consume a device's I/O
parameters. These utilities will not allow a file system to be formatted to use a block size smaller than
the logical_block_size of the underlying storage device.
Except for mkfs.gfs2, all other mkfs.filesystem utilities also use the I/O hints to layout on-disk
data structure and data areas relative to the minimum_io_size and optimal_io_size of the
underlying storage device. This allows file systems to be optimally formatted for various RAID (striped)
layouts.