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Based on kernel version 3.3. Page generated on 2012-03-23 21:22 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/write_generate
57	Date:		June 2008
58	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
59	Description:
60			Indicates whether the block layer should automatically
61			generate checksums for write requests bound for
62			devices that support receiving integrity metadata.
63	
64	What:		/sys/block/<disk>/alignment_offset
65	Date:		April 2009
66	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
67	Description:
68			Storage devices may report a physical block size that is
69			bigger than the logical block size (for instance a drive
70			with 4KB physical sectors exposing 512-byte logical
71			blocks to the operating system).  This parameter
72			indicates how many bytes the beginning of the device is
73			offset from the disk's natural alignment.
74	
75	What:		/sys/block/<disk>/<partition>/alignment_offset
76	Date:		April 2009
77	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
78	Description:
79			Storage devices may report a physical block size that is
80			bigger than the logical block size (for instance a drive
81			with 4KB physical sectors exposing 512-byte logical
82			blocks to the operating system).  This parameter
83			indicates how many bytes the beginning of the partition
84			is offset from the disk's natural alignment.
85	
86	What:		/sys/block/<disk>/queue/logical_block_size
87	Date:		May 2009
88	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
89	Description:
90			This is the smallest unit the storage device can
91			address.  It is typically 512 bytes.
92	
93	What:		/sys/block/<disk>/queue/physical_block_size
94	Date:		May 2009
95	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
96	Description:
97			This is the smallest unit a physical storage device can
98			write atomically.  It is usually the same as the logical
99			block size but may be bigger.  One example is SATA
100			drives with 4KB sectors that expose a 512-byte logical
101			block size to the operating system.  For stacked block
102			devices the physical_block_size variable contains the
103			maximum physical_block_size of the component devices.
104	
105	What:		/sys/block/<disk>/queue/minimum_io_size
106	Date:		April 2009
107	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
108	Description:
109			Storage devices may report a granularity or preferred
110			minimum I/O size which is the smallest request the
111			device can perform without incurring a performance
112			penalty.  For disk drives this is often the physical
113			block size.  For RAID arrays it is often the stripe
114			chunk size.  A properly aligned multiple of
115			minimum_io_size is the preferred request size for
116			workloads where a high number of I/O operations is
117			desired.
118	
119	What:		/sys/block/<disk>/queue/optimal_io_size
120	Date:		April 2009
121	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
122	Description:
123			Storage devices may report an optimal I/O size, which is
124			the device's preferred unit for sustained I/O.  This is
125			rarely reported for disk drives.  For RAID arrays it is
126			usually the stripe width or the internal track size.  A
127			properly aligned multiple of optimal_io_size is the
128			preferred request size for workloads where sustained
129			throughput is desired.  If no optimal I/O size is
130			reported this file contains 0.
131	
132	What:		/sys/block/<disk>/queue/nomerges
133	Date:		January 2010
134	Contact:
135	Description:
136			Standard I/O elevator operations include attempts to
137			merge contiguous I/Os. For known random I/O loads these
138			attempts will always fail and result in extra cycles
139			being spent in the kernel. This allows one to turn off
140			this behavior on one of two ways: When set to 1, complex
141			merge checks are disabled, but the simple one-shot merges
142			with the previous I/O request are enabled. When set to 2,
143			all merge tries are disabled. The default value is 0 -
144			which enables all types of merge tries.
145	
146	What:		/sys/block/<disk>/discard_alignment
147	Date:		May 2011
148	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
149	Description:
150			Devices that support discard functionality may
151			internally allocate space in units that are bigger than
152			the exported logical block size. The discard_alignment
153			parameter indicates how many bytes the beginning of the
154			device is offset from the internal allocation unit's
155			natural alignment.
156	
157	What:		/sys/block/<disk>/<partition>/discard_alignment
158	Date:		May 2011
159	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
160	Description:
161			Devices that support discard functionality may
162			internally allocate space in units that are bigger than
163			the exported logical block size. The discard_alignment
164			parameter indicates how many bytes the beginning of the
165			partition is offset from the internal allocation unit's
166			natural alignment.
167	
168	What:		/sys/block/<disk>/queue/discard_granularity
169	Date:		May 2011
170	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
171	Description:
172			Devices that support discard functionality may
173			internally allocate space using units that are bigger
174			than the logical block size. The discard_granularity
175			parameter indicates the size of the internal allocation
176			unit in bytes if reported by the device. Otherwise the
177			discard_granularity will be set to match the device's
178			physical block size. A discard_granularity of 0 means
179			that the device does not support discard functionality.
180	
181	What:		/sys/block/<disk>/queue/discard_max_bytes
182	Date:		May 2011
183	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
184	Description:
185			Devices that support discard functionality may have
186			internal limits on the number of bytes that can be
187			trimmed or unmapped in a single operation. Some storage
188			protocols also have inherent limits on the number of
189			blocks that can be described in a single command. The
190			discard_max_bytes parameter is set by the device driver
191			to the maximum number of bytes that can be discarded in
192			a single operation. Discard requests issued to the
193			device must not exceed this limit. A discard_max_bytes
194			value of 0 means that the device does not support
195			discard functionality.
196	
197	What:		/sys/block/<disk>/queue/discard_zeroes_data
198	Date:		May 2011
199	Contact:	Martin K. Petersen <martin.petersen@oracle.com>
200	Description:
201			Devices that support discard functionality may return
202			stale or random data when a previously discarded block
203			is read back. This can cause problems if the filesystem
204			expects discarded blocks to be explicitly cleared. If a
205			device reports that it deterministically returns zeroes
206			when a discarded area is read the discard_zeroes_data
207			parameter will be set to one. Otherwise it will be 0 and
208			the result of reading a discarded area is undefined.
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