when a discarded area is read the discard_zeroes_data
parameter will be set to one. Otherwise it will be 0 and
the result of reading a discarded area is undefined.
-What: /sys/block/<disk>/alias
-Date: Aug 2011
-Contact: Nao Nishijima <nao.nishijima.xt@hitachi.com>
-Description:
- A raw device name of a disk does not always point a same disk
- each boot-up time. Therefore, users have to use persistent
- device names, which udev creates when the kernel finds a disk,
- instead of raw device name. However, kernel doesn't show those
- persistent names on its messages (e.g. dmesg).
- This file can store an alias of the disk and it would be
- appeared in kernel messages if it is set. A disk can have an
- alias which length is up to 255bytes. Users can use alphabets,
- numbers, "-" and "_" in alias name. This file is writeonce.
+
+What: /sys/block/<disk>/queue/write_same_max_bytes
+Date: January 2012
+Contact: Martin K. Petersen <martin.petersen@oracle.com>
+Description:
+ Some devices support a write same operation in which a
+ single data block can be written to a range of several
+ contiguous blocks on storage. This can be used to wipe
+ areas on disk or to initialize drives in a RAID
+ configuration. write_same_max_bytes indicates how many
+ bytes can be written in a single write same command. If
+ write_same_max_bytes is 0, write same is not supported
+ by the device.
+