<s>
iostat	B-Device
(	O
input/output	B-General_Concept
statistics	O
)	O
is	O
a	O
computer	O
system	B-Application
monitor	I-Application
tool	O
used	O
to	O
collect	O
and	O
show	O
operating	B-General_Concept
system	I-General_Concept
storage	B-General_Concept
input	B-General_Concept
and	I-General_Concept
output	I-General_Concept
statistics	O
.	O
</s>
<s>
It	O
is	O
often	O
used	O
to	O
identify	O
performance	O
issues	O
with	O
storage	B-General_Concept
devices	O
,	O
including	O
local	O
disks	B-Device
,	O
or	O
remote	O
disks	B-Device
accessed	O
over	O
network	B-Protocol
file	I-Protocol
systems	I-Protocol
such	O
as	O
NFS	B-Protocol
.	O
</s>
<s>
It	O
can	O
also	O
be	O
used	O
to	O
provide	O
information	O
about	O
terminal	B-General_Concept
(	O
TTY	O
)	O
input	B-General_Concept
and	I-General_Concept
output	I-General_Concept
,	O
and	O
also	O
includes	O
some	O
basic	O
CPU	O
information	O
.	O
</s>
<s>
iostat	B-Device
-x	O
displays	O
output	O
where	O
each	O
line	O
(	O
row	O
)	O
gives	O
numerical	O
data	O
for	O
one	O
device	O
.	O
</s>
<s>
It	O
is	O
best	O
to	O
run	O
iostat	B-Device
specifying	O
a	O
time	O
interval	O
in	O
seconds	O
(	O
for	O
example	O
iostat	B-Device
-x	O
30	O
)	O
in	O
order	O
to	O
see	O
the	O
results	O
over	O
time	O
.	O
</s>
<s>
This	O
is	O
because	O
otherwise	O
,	O
the	O
output	O
will	O
reflect	O
the	O
values	O
over	O
the	O
entire	O
timespan	O
since	O
the	O
system	O
was	O
last	O
rebooted	B-Device
.	O
</s>
<s>
The	O
iostat	B-Device
tool	O
is	O
available	O
on	O
most	O
Unix	B-Application
and	O
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
,	O
such	O
as	O
FreeBSD	B-Operating_System
,	O
macOS	B-Application
(	O
com.apple.pkg.Core	O
package	O
)	O
,	O
Linux	B-Application
(	O
sysstat	B-Application
package	O
)	O
,	O
and	O
Solaris	B-Application
.	O
</s>
<s>
The	O
syntax	O
and	O
output	O
of	O
iostat	B-Device
often	O
differs	O
slightly	O
between	O
them	O
.	O
</s>
<s>
Sun	O
Microsystems	O
stated	O
that	O
high	O
values	O
in	O
the	O
wait	O
and	O
svc_t	O
fields	O
suggest	O
a	O
lack	O
of	O
overall	O
throughput	O
in	O
the	O
system	O
,	O
indicating	O
that	O
"	O
the	O
system	O
is	O
overloaded	O
with	O
I/O	B-General_Concept
operations	I-General_Concept
"	O
.	O
</s>
<s>
Consistently	O
high	O
values	O
in	O
the	O
kr/s	O
,	O
kw/s	O
,	O
%w	O
and	O
%b	O
fields	O
also	O
indicate	O
"	O
a	O
possible	O
I/O	B-General_Concept
bottleneck	O
"	O
.	O
</s>
<s>
In	O
versions	O
of	O
Solaris	B-Application
before	O
Solaris	B-Application
7	I-Application
,	O
iostat	B-Device
can	O
give	O
misleading	O
information	O
in	O
the	O
wait	O
field	O
on	O
multiprocessor	B-Operating_System
systems	O
.	O
</s>
<s>
This	O
is	O
because	O
iostat	B-Device
can	O
misinterpret	O
one	O
processor	B-General_Concept
being	O
in	O
a	O
state	O
where	O
it	O
is	O
waiting	O
for	O
I/O	B-General_Concept
,	O
as	O
meaning	O
that	O
all	O
processors	O
in	O
the	O
system	O
are	O
having	O
to	O
wait	O
.	O
</s>
<s>
It	O
is	O
also	O
advisable	O
to	O
disregard	O
high	O
values	O
in	O
the	O
svc_t	O
field	O
for	O
disks	B-Device
that	O
have	O
very	O
low	O
rates	O
of	O
activity	O
(	O
less	O
than	O
5%	O
)	O
.	O
</s>
<s>
This	O
is	O
because	O
the	O
fsflush	O
process	O
can	O
force	O
up	O
the	O
average	O
service	O
time	O
when	O
synchronising	O
data	O
on	O
disk	B-Device
with	O
what	O
is	O
in	O
memory	O
.	O
</s>
<s>
iostat	B-Device
does	O
not	O
display	O
information	O
about	O
the	O
individual	O
volumes	O
on	O
each	O
disk	B-Device
if	O
a	O
volume	B-Application
manager	I-Application
is	O
used	O
.	O
</s>
<s>
The	O
vxstat	O
command	B-Application
can	O
be	O
used	O
to	O
show	O
this	O
information	O
instead	O
.	O
</s>
<s>
In	O
contrast	O
,	O
when	O
using	O
Linux	B-Application
LVM	I-Application
as	O
a	O
volume	B-Application
manager	I-Application
,	O
iostat	B-Device
does	O
display	O
volume	O
information	O
individually	O
,	O
because	O
each	O
logical	B-Application
volume	I-Application
has	O
its	O
own	O
device	B-Application
mapper	I-Application
(	O
dm	O
)	O
device	O
.	O
</s>
