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29 .Dd March 16, 2022
30 .Dt ZPOOL-IOSTAT 8
31 .Os
32 .
33 .Sh NAME
34 .Nm zpool-iostat
35 .Nd display logical I/O statistics for ZFS storage pools
36 .Sh SYNOPSIS
37 .Nm zpool
38 .Cm iostat
39 .Op Oo Oo Fl c Ar SCRIPT Oc Oo Fl lq Oc Oc Ns | Ns Fl rw
40 .Op Fl T Sy u Ns | Ns Sy d
41 .Op Fl ghHLnpPvy
42 .Oo Ar pool Ns … Ns | Ns Oo Ar pool vdev Ns … Oc Ns | Ns Ar vdev Ns … Oc
43 .Op Ar interval Op Ar count
44 .
45 .Sh DESCRIPTION
46 Displays logical I/O statistics for the given pools/vdevs.
47 Physical I/O statistics may be observed via
48 .Xr iostat 1 .
49 If writes are located nearby, they may be merged into a single
50 larger operation.
51 Additional I/O may be generated depending on the level of vdev redundancy.
52 To filter output, you may pass in a list of pools, a pool and list of vdevs
53 in that pool, or a list of any vdevs from any pool.
54 If no items are specified, statistics for every pool in the system are shown.
55 When given an
56 .Ar interval ,
57 the statistics are printed every
58 .Ar interval
59 seconds until killed.
60 If
61 .Fl n
62 flag is specified the headers are displayed only once, otherwise they are
63 displayed periodically.
64 If
65 .Ar count
66 is specified, the command exits after
67 .Ar count
68 reports are printed.
69 The first report printed is always the statistics since boot regardless of
70 whether
71 .Ar interval
72 and
73 .Ar count
74 are passed.
75 However, this behavior can be suppressed with the
76 .Fl y
77 flag.
78 Also note that the units of
79 .Sy K ,
80 .Sy M ,
81 .Sy G Ns …
82 that are printed in the report are in base 1024.
83 To get the raw values, use the
84 .Fl p
85 flag.
86 .Bl -tag -width Ds
87 .It Fl c Op Ar SCRIPT1 Ns Oo , Ns Ar SCRIPT2 Oc Ns …
88 Run a script (or scripts) on each vdev and include the output as a new column
89 in the
90 .Nm zpool Cm iostat
91 output.
92 Users can run any script found in their
93 .Pa ~/.zpool.d
94 directory or from the system
95 .Pa /etc/zfs/zpool.d
96 directory.
97 Script names containing the slash
98 .Pq Sy /
99 character are not allowed.
100 The default search path can be overridden by setting the
101 .Sy ZPOOL_SCRIPTS_PATH
102 environment variable.
103 A privileged user can only run
104 .Fl c
105 if they have the
106 .Sy ZPOOL_SCRIPTS_AS_ROOT
107 environment variable set.
108 If a script requires the use of a privileged command, like
109 .Xr smartctl 8 ,
110 then it's recommended you allow the user access to it in
111 .Pa /etc/sudoers
112 or add the user to the
113 .Pa /etc/sudoers.d/zfs
114 file.
115 .Pp
116 If
117 .Fl c
118 is passed without a script name, it prints a list of all scripts.
119 .Fl c
120 also sets verbose mode
121 .No \&( Ns Fl v Ns No \&) .
122 .Pp
123 Script output should be in the form of "name=value".
124 The column name is set to "name" and the value is set to "value".
125 Multiple lines can be used to output multiple columns.
126 The first line of output not in the
127 "name=value" format is displayed without a column title,
128 and no more output after that is displayed.
129 This can be useful for printing error messages.
130 Blank or NULL values are printed as a '-' to make output AWKable.
131 .Pp
132 The following environment variables are set before running each script:
133 .Bl -tag -compact -width "VDEV_ENC_SYSFS_PATH"
134 .It Sy VDEV_PATH
135 Full path to the vdev
136 .It Sy VDEV_UPATH
137 Underlying path to the vdev
138 .Pq Pa /dev/sd* .
139 For use with device mapper, multipath, or partitioned vdevs.
140 .It Sy VDEV_ENC_SYSFS_PATH
141 The sysfs path to the enclosure for the vdev (if any).
142 .El
143 .It Fl T Sy u Ns | Ns Sy d
144 Display a time stamp.
145 Specify
146 .Sy u
147 for a printed representation of the internal representation of time.
148 See
149 .Xr time 2 .
150 Specify
151 .Sy d
152 for standard date format.
153 See
154 .Xr date 1 .
155 .It Fl g
156 Display vdev GUIDs instead of the normal device names.
157 These GUIDs can be used in place of device names for the zpool
158 detach/offline/remove/replace commands.
159 .It Fl H
160 Scripted mode.
161 Do not display headers, and separate fields by a
162 single tab instead of arbitrary space.
163 .It Fl L
164 Display real paths for vdevs resolving all symbolic links.
165 This can be used to look up the current block device name regardless of the
166 .Pa /dev/disk/
167 path used to open it.
168 .It Fl n
169 Print headers only once when passed
170 .It Fl p
171 Display numbers in parsable (exact) values.
172 Time values are in nanoseconds.
173 .It Fl P
174 Display full paths for vdevs instead of only the last component of the path.
175 This can be used in conjunction with the
176 .Fl L
177 flag.
178 .It Fl r
179 Print request size histograms for the leaf vdev's I/O.
180 This includes histograms of individual I/O (ind) and aggregate I/O (agg).
181 These stats can be useful for observing how well I/O aggregation is working.
182 Note that TRIM I/O may exceed 16M, but will be counted as 16M.
183 .It Fl v
184 Verbose statistics Reports usage statistics for individual vdevs within the
185 pool, in addition to the pool-wide statistics.
186 .It Fl y
187 Normally the first line of output reports the statistics since boot:
188 suppress it.
189 .It Fl w
190 Display latency histograms:
191 .Bl -tag -compact -width "asyncq_read/write"
192 .It Sy total_wait
193 Total I/O time (queuing + disk I/O time).
194 .It Sy disk_wait
195 Disk I/O time (time reading/writing the disk).
196 .It Sy syncq_wait
197 Amount of time I/O spent in synchronous priority queues.
198 Does not include disk time.
199 .It Sy asyncq_wait
200 Amount of time I/O spent in asynchronous priority queues.
201 Does not include disk time.
202 .It Sy scrub
203 Amount of time I/O spent in scrub queue.
204 Does not include disk time.
205 .It Sy rebuild
206 Amount of time I/O spent in rebuild queue.
207 Does not include disk time.
208 .El
209 .It Fl l
210 Include average latency statistics:
211 .Bl -tag -compact -width "asyncq_read/write"
212 .It Sy total_wait
213 Average total I/O time (queuing + disk I/O time).
214 .It Sy disk_wait
215 Average disk I/O time (time reading/writing the disk).
216 .It Sy syncq_wait
217 Average amount of time I/O spent in synchronous priority queues.
218 Does not include disk time.
219 .It Sy asyncq_wait
220 Average amount of time I/O spent in asynchronous priority queues.
221 Does not include disk time.
222 .It Sy scrub
223 Average queuing time in scrub queue.
224 Does not include disk time.
225 .It Sy trim
226 Average queuing time in trim queue.
227 Does not include disk time.
228 .It Sy rebuild
229 Average queuing time in rebuild queue.
230 Does not include disk time.
231 .El
232 .It Fl q
233 Include active queue statistics.
234 Each priority queue has both pending
235 .Sy ( pend )
236 and active
237 .Sy ( activ )
238 I/O requests.
239 Pending requests are waiting to be issued to the disk,
240 and active requests have been issued to disk and are waiting for completion.
241 These stats are broken out by priority queue:
242 .Bl -tag -compact -width "asyncq_read/write"
243 .It Sy syncq_read/write
244 Current number of entries in synchronous priority
245 queues.
246 .It Sy asyncq_read/write
247 Current number of entries in asynchronous priority queues.
248 .It Sy scrubq_read
249 Current number of entries in scrub queue.
250 .It Sy trimq_write
251 Current number of entries in trim queue.
252 .It Sy rebuildq_write
253 Current number of entries in rebuild queue.
254 .El
255 .Pp
256 All queue statistics are instantaneous measurements of the number of
257 entries in the queues.
258 If you specify an interval,
259 the measurements will be sampled from the end of the interval.
260 .El
261 .
262 .Sh EXAMPLES
263 .\" These are, respectively, examples 13, 16 from zpool.8
264 .\" Make sure to update them bidirectionally
265 .Ss Example 13 : No Adding Cache Devices to a ZFS Pool
266 The following command adds two disks for use as cache devices to a ZFS storage
267 pool:
268 .Dl # Nm zpool Cm add Ar pool Sy cache Pa sdc sdd
269 .Pp
270 Once added, the cache devices gradually fill with content from main memory.
271 Depending on the size of your cache devices, it could take over an hour for
272 them to fill.
273 Capacity and reads can be monitored using the
274 .Cm iostat
275 subcommand as follows:
276 .Dl # Nm zpool Cm iostat Fl v Ar pool 5
277 .
278 .Ss Example 16 : No Adding output columns
279 Additional columns can be added to the
280 .Nm zpool Cm status No and Nm zpool Cm iostat No output with Fl c .
281 .Bd -literal -compact -offset Ds
282 .No # Nm zpool Cm status Fl c Pa vendor , Ns Pa model , Ns Pa size
283 NAME STATE READ WRITE CKSUM vendor model size
284 tank ONLINE 0 0 0
285 mirror-0 ONLINE 0 0 0
286 U1 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T
287 U10 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T
288 U11 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T
289 U12 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T
290 U13 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T
291 U14 ONLINE 0 0 0 SEAGATE ST8000NM0075 7.3T
293 .No # Nm zpool Cm iostat Fl vc Pa size
294 capacity operations bandwidth
295 pool alloc free read write read write size
296 ---------- ----- ----- ----- ----- ----- ----- ----
297 rpool 14.6G 54.9G 4 55 250K 2.69M
298 sda1 14.6G 54.9G 4 55 250K 2.69M 70G
299 ---------- ----- ----- ----- ----- ----- ----- ----
300 .Ed
301 .
302 .Sh SEE ALSO
303 .Xr iostat 1 ,
304 .Xr smartctl 8 ,
305 .Xr zpool-list 8 ,
306 .Xr zpool-status 8