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Based on kernel version 4.0. Page generated on 2015-04-14 21:19 EST.

1	What:		/sys/block/<disk>/stat
2	Date:		February 2008
3	Contact:	Jerome Marchand <jmarchan@redhat.com>
4	Description:
5			The /sys/block/<disk>/stat files displays the I/O
6			statistics of disk <disk>. They contain 11 fields:
7			 1 - reads completed successfully
8			 2 - reads merged
9			 3 - sectors read
10			 4 - time spent reading (ms)
11			 5 - writes completed
12			 6 - writes merged
13			 7 - sectors written
14			 8 - time spent writing (ms)
15			 9 - I/Os currently in progress
16			10 - time spent doing I/Os (ms)
17			11 - weighted time spent doing I/Os (ms)
18			For more details refer Documentation/iostats.txt
19	
20	
21	What:		/sys/block/<disk>/<part>/stat
22	Date:		February 2008
23	Contact:	Jerome Marchand <jmarchan@redhat.com>
24	Description:
25			The /sys/block/<disk>/<part>/stat files display the
26			I/O statistics of partition <part>. The format is the
27			same as the above-written /sys/block/<disk>/stat
28			format.
29	
30	
31	What:		/sys/block/<disk>/integrity/format
32	Date:		June 2008
33	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
34	Description:
35			Metadata format for integrity capable block device.
36			E.g. T10-DIF-TYPE1-CRC.
37	
38	
39	What:		/sys/block/<disk>/integrity/read_verify
40	Date:		June 2008
41	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
42	Description:
43			Indicates whether the block layer should verify the
44			integrity of read requests serviced by devices that
45			support sending integrity metadata.
46	
47	
48	What:		/sys/block/<disk>/integrity/tag_size
49	Date:		June 2008
50	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
51	Description:
52			Number of bytes of integrity tag space available per
53			512 bytes of data.
54	
55	
56	What:		/sys/block/<disk>/integrity/device_is_integrity_capable
57	Date:		July 2014
58	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
59	Description:
60			Indicates whether a storage device is capable of storing
61			integrity metadata. Set if the device is T10 PI-capable.
62	
63	
64	What:		/sys/block/<disk>/integrity/write_generate
65	Date:		June 2008
66	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
67	Description:
68			Indicates whether the block layer should automatically
69			generate checksums for write requests bound for
70			devices that support receiving integrity metadata.
71	
72	What:		/sys/block/<disk>/alignment_offset
73	Date:		April 2009
74	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
75	Description:
76			Storage devices may report a physical block size that is
77			bigger than the logical block size (for instance a drive
78			with 4KB physical sectors exposing 512-byte logical
79			blocks to the operating system).  This parameter
80			indicates how many bytes the beginning of the device is
81			offset from the disk's natural alignment.
82	
83	What:		/sys/block/<disk>/<partition>/alignment_offset
84	Date:		April 2009
85	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
86	Description:
87			Storage devices may report a physical block size that is
88			bigger than the logical block size (for instance a drive
89			with 4KB physical sectors exposing 512-byte logical
90			blocks to the operating system).  This parameter
91			indicates how many bytes the beginning of the partition
92			is offset from the disk's natural alignment.
93	
94	What:		/sys/block/<disk>/queue/logical_block_size
95	Date:		May 2009
96	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
97	Description:
98			This is the smallest unit the storage device can
99			address.  It is typically 512 bytes.
100	
101	What:		/sys/block/<disk>/queue/physical_block_size
102	Date:		May 2009
103	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
104	Description:
105			This is the smallest unit a physical storage device can
106			write atomically.  It is usually the same as the logical
107			block size but may be bigger.  One example is SATA
108			drives with 4KB sectors that expose a 512-byte logical
109			block size to the operating system.  For stacked block
110			devices the physical_block_size variable contains the
111			maximum physical_block_size of the component devices.
112	
113	What:		/sys/block/<disk>/queue/minimum_io_size
114	Date:		April 2009
115	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
116	Description:
117			Storage devices may report a granularity or preferred
118			minimum I/O size which is the smallest request the
119			device can perform without incurring a performance
120			penalty.  For disk drives this is often the physical
121			block size.  For RAID arrays it is often the stripe
122			chunk size.  A properly aligned multiple of
123			minimum_io_size is the preferred request size for
124			workloads where a high number of I/O operations is
125			desired.
126	
127	What:		/sys/block/<disk>/queue/optimal_io_size
128	Date:		April 2009
129	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
130	Description:
131			Storage devices may report an optimal I/O size, which is
132			the device's preferred unit for sustained I/O.  This is
133			rarely reported for disk drives.  For RAID arrays it is
134			usually the stripe width or the internal track size.  A
135			properly aligned multiple of optimal_io_size is the
136			preferred request size for workloads where sustained
137			throughput is desired.  If no optimal I/O size is
138			reported this file contains 0.
139	
140	What:		/sys/block/<disk>/queue/nomerges
141	Date:		January 2010
142	Contact:
143	Description:
144			Standard I/O elevator operations include attempts to
145			merge contiguous I/Os. For known random I/O loads these
146			attempts will always fail and result in extra cycles
147			being spent in the kernel. This allows one to turn off
148			this behavior on one of two ways: When set to 1, complex
149			merge checks are disabled, but the simple one-shot merges
150			with the previous I/O request are enabled. When set to 2,
151			all merge tries are disabled. The default value is 0 -
152			which enables all types of merge tries.
153	
154	What:		/sys/block/<disk>/discard_alignment
155	Date:		May 2011
156	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
157	Description:
158			Devices that support discard functionality may
159			internally allocate space in units that are bigger than
160			the exported logical block size. The discard_alignment
161			parameter indicates how many bytes the beginning of the
162			device is offset from the internal allocation unit's
163			natural alignment.
164	
165	What:		/sys/block/<disk>/<partition>/discard_alignment
166	Date:		May 2011
167	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
168	Description:
169			Devices that support discard functionality may
170			internally allocate space in units that are bigger than
171			the exported logical block size. The discard_alignment
172			parameter indicates how many bytes the beginning of the
173			partition is offset from the internal allocation unit's
174			natural alignment.
175	
176	What:		/sys/block/<disk>/queue/discard_granularity
177	Date:		May 2011
178	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
179	Description:
180			Devices that support discard functionality may
181			internally allocate space using units that are bigger
182			than the logical block size. The discard_granularity
183			parameter indicates the size of the internal allocation
184			unit in bytes if reported by the device. Otherwise the
185			discard_granularity will be set to match the device's
186			physical block size. A discard_granularity of 0 means
187			that the device does not support discard functionality.
188	
189	What:		/sys/block/<disk>/queue/discard_max_bytes
190	Date:		May 2011
191	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
192	Description:
193			Devices that support discard functionality may have
194			internal limits on the number of bytes that can be
195			trimmed or unmapped in a single operation. Some storage
196			protocols also have inherent limits on the number of
197			blocks that can be described in a single command. The
198			discard_max_bytes parameter is set by the device driver
199			to the maximum number of bytes that can be discarded in
200			a single operation. Discard requests issued to the
201			device must not exceed this limit. A discard_max_bytes
202			value of 0 means that the device does not support
203			discard functionality.
204	
205	What:		/sys/block/<disk>/queue/discard_zeroes_data
206	Date:		May 2011
207	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
208	Description:
209			Devices that support discard functionality may return
210			stale or random data when a previously discarded block
211			is read back. This can cause problems if the filesystem
212			expects discarded blocks to be explicitly cleared. If a
213			device reports that it deterministically returns zeroes
214			when a discarded area is read the discard_zeroes_data
215			parameter will be set to one. Otherwise it will be 0 and
216			the result of reading a discarded area is undefined.
217	
218	What:		/sys/block/<disk>/queue/write_same_max_bytes
219	Date:		January 2012
220	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
221	Description:
222			Some devices support a write same operation in which a
223			single data block can be written to a range of several
224			contiguous blocks on storage. This can be used to wipe
225			areas on disk or to initialize drives in a RAID
226			configuration. write_same_max_bytes indicates how many
227			bytes can be written in a single write same command. If
228			write_same_max_bytes is 0, write same is not supported
229			by the device.
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