IO Wait is consistently touching high values around 60-70% during load run
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I am stuck on an IOwait related problem, the server I am monitoring shows a very high value for IOwait during my load run time (50%-70%). I generated this data using the SAR report command. The ideal value should be below 8%-9% as the server has 12 cores(1/12 ~ 0.08). I read this somewhere and took the assumption accordingly.
What can be done to rectify this high IOwait problem, how is it related to other factors in the server which can be checked for to improve the performance.
disk io sar
asked Aug 21 at 9:10
M. Rafi
11
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I am stuck on an IOwait related problem, the server I am monitoring shows a very high value for IOwait during my load run time (50%-70%). I generated this data using the SAR report command. The ideal value should be below 8%-9% as the server has 12 cores(1/12 ~ 0.08). I read this somewhere and took the assumption accordingly.
What can be done to rectify this high IOwait problem, how is it related to other factors in the server which can be checked for to improve the performance.
disk io sar
asked Aug 21 at 9:10
M. Rafi
11
1
Could you please provide physical disk model?ls /dev/disk/by-id/or something. Honestly, I haven't heard of a disk with cores and I am very curious.
– mikst
Aug 21 at 9:36
Sorry, I rectified the mistake, the server has 12 cores.
– M. Rafi
Aug 21 at 9:48
add a comment |Â
up vote
0
down vote
favorite
up vote
0
down vote
favorite
I am stuck on an IOwait related problem, the server I am monitoring shows a very high value for IOwait during my load run time (50%-70%). I generated this data using the SAR report command. The ideal value should be below 8%-9% as the server has 12 cores(1/12 ~ 0.08). I read this somewhere and took the assumption accordingly.
What can be done to rectify this high IOwait problem, how is it related to other factors in the server which can be checked for to improve the performance.
disk io sar
asked Aug 21 at 9:10
M. Rafi
11
I am stuck on an IOwait related problem, the server I am monitoring shows a very high value for IOwait during my load run time (50%-70%). I generated this data using the SAR report command. The ideal value should be below 8%-9% as the server has 12 cores(1/12 ~ 0.08). I read this somewhere and took the assumption accordingly.
What can be done to rectify this high IOwait problem, how is it related to other factors in the server which can be checked for to improve the performance.
disk io sar
disk io sar
asked Aug 21 at 9:10
M. Rafi
11
asked Aug 21 at 9:10
M. Rafi
11
edited Aug 21 at 9:47
asked Aug 21 at 9:10
M. Rafi
11
asked Aug 21 at 9:10
M. Rafi
11
asked Aug 21 at 9:10
M. Rafi
11
11
1
Could you please provide physical disk model?ls /dev/disk/by-id/or something. Honestly, I haven't heard of a disk with cores and I am very curious.
– mikst
Aug 21 at 9:36
Sorry, I rectified the mistake, the server has 12 cores.
– M. Rafi
Aug 21 at 9:48
add a comment |Â
1
Could you please provide physical disk model?ls /dev/disk/by-id/or something. Honestly, I haven't heard of a disk with cores and I am very curious.
– mikst
Aug 21 at 9:36
Sorry, I rectified the mistake, the server has 12 cores.
– M. Rafi
Aug 21 at 9:48
1
1
Could you please provide physical disk model?
ls /dev/disk/by-id/ or something. Honestly, I haven't heard of a disk with cores and I am very curious.– mikst
Aug 21 at 9:36
Could you please provide physical disk model?
ls /dev/disk/by-id/ or something. Honestly, I haven't heard of a disk with cores and I am very curious.– mikst
Aug 21 at 9:36
Sorry, I rectified the mistake, the server has 12 cores.
– M. Rafi
Aug 21 at 9:48
Sorry, I rectified the mistake, the server has 12 cores.
– M. Rafi
Aug 21 at 9:48
add a comment |Â
2 Answers
2
active
oldest
votes
up vote
0
down vote
The more powerful is CPU the greater iowait, not the other way around.
In general in order to reduce iowait this can help:
Optimising application code if possible/applicable, for example suboptimal database query can force DBMS execute inefficient plan and cause excessive disk load.
Getting more RAM if your load is heavy on reads.
Making storage subsystem faster. Faster disks, faster RAID, faster storage controller, write-back caching. That's a science on it's own.
Sorry, with generic question like that, there is only a generic answer.
answered Aug 21 at 9:59
mikst
967
Thank you @mikst, I'll dig deep into the inputs you have given and ask for more specific inputs.
– M. Rafi
Aug 21 at 10:26
add a comment |Â
up vote
0
down vote
Allow me to reveal the small Linux secret: there is no reliable iowait statistics in Linux. This is only truth. From PROC(5) we read:
iowait (since Linux 2.5.41)
(5) Time waiting for I/O to complete. This value is not reliable, for
the following reasons:
The CPU will not wait for I/O to complete; iowait is the time that a task is waiting for I/O to complete. When a CPU goes into idle
state for outstanding task I/O, another task will be scheduled on this
CPU.
On a multi-core CPU, the task waiting for I/O to complete is not running on any CPU, so the iowait of each CPU is difficult to
calculate.
The value in this field may decrease in certain conditions.
So, my suggestion for is to forget about iowait measurements in Linux.
answered Aug 21 at 10:42
Bob
72017
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
0
down vote
The more powerful is CPU the greater iowait, not the other way around.
In general in order to reduce iowait this can help:
Optimising application code if possible/applicable, for example suboptimal database query can force DBMS execute inefficient plan and cause excessive disk load.
Getting more RAM if your load is heavy on reads.
Making storage subsystem faster. Faster disks, faster RAID, faster storage controller, write-back caching. That's a science on it's own.
Sorry, with generic question like that, there is only a generic answer.
answered Aug 21 at 9:59
mikst
967
Thank you @mikst, I'll dig deep into the inputs you have given and ask for more specific inputs.
– M. Rafi
Aug 21 at 10:26
add a comment |Â
up vote
0
down vote
The more powerful is CPU the greater iowait, not the other way around.
In general in order to reduce iowait this can help:
Optimising application code if possible/applicable, for example suboptimal database query can force DBMS execute inefficient plan and cause excessive disk load.
Getting more RAM if your load is heavy on reads.
Making storage subsystem faster. Faster disks, faster RAID, faster storage controller, write-back caching. That's a science on it's own.
Sorry, with generic question like that, there is only a generic answer.
answered Aug 21 at 9:59
mikst
967
Thank you @mikst, I'll dig deep into the inputs you have given and ask for more specific inputs.
– M. Rafi
Aug 21 at 10:26
add a comment |Â
up vote
0
down vote
up vote
0
down vote
The more powerful is CPU the greater iowait, not the other way around.
In general in order to reduce iowait this can help:
Optimising application code if possible/applicable, for example suboptimal database query can force DBMS execute inefficient plan and cause excessive disk load.
Getting more RAM if your load is heavy on reads.
Making storage subsystem faster. Faster disks, faster RAID, faster storage controller, write-back caching. That's a science on it's own.
Sorry, with generic question like that, there is only a generic answer.
answered Aug 21 at 9:59
mikst
967
The more powerful is CPU the greater iowait, not the other way around.
In general in order to reduce iowait this can help:
Optimising application code if possible/applicable, for example suboptimal database query can force DBMS execute inefficient plan and cause excessive disk load.
Getting more RAM if your load is heavy on reads.
Making storage subsystem faster. Faster disks, faster RAID, faster storage controller, write-back caching. That's a science on it's own.
Sorry, with generic question like that, there is only a generic answer.
answered Aug 21 at 9:59
mikst
967
answered Aug 21 at 9:59
mikst
967
answered Aug 21 at 9:59
mikst
967
answered Aug 21 at 9:59
mikst
967
967
Thank you @mikst, I'll dig deep into the inputs you have given and ask for more specific inputs.
– M. Rafi
Aug 21 at 10:26
add a comment |Â
Thank you @mikst, I'll dig deep into the inputs you have given and ask for more specific inputs.
– M. Rafi
Aug 21 at 10:26
Thank you @mikst, I'll dig deep into the inputs you have given and ask for more specific inputs.
– M. Rafi
Aug 21 at 10:26
Thank you @mikst, I'll dig deep into the inputs you have given and ask for more specific inputs.
– M. Rafi
Aug 21 at 10:26
add a comment |Â
up vote
0
down vote
Allow me to reveal the small Linux secret: there is no reliable iowait statistics in Linux. This is only truth. From PROC(5) we read:
iowait (since Linux 2.5.41)
(5) Time waiting for I/O to complete. This value is not reliable, for
the following reasons:
The CPU will not wait for I/O to complete; iowait is the time that a task is waiting for I/O to complete. When a CPU goes into idle
state for outstanding task I/O, another task will be scheduled on this
CPU.
On a multi-core CPU, the task waiting for I/O to complete is not running on any CPU, so the iowait of each CPU is difficult to
calculate.
The value in this field may decrease in certain conditions.
So, my suggestion for is to forget about iowait measurements in Linux.
answered Aug 21 at 10:42
Bob
72017
add a comment |Â
up vote
0
down vote
Allow me to reveal the small Linux secret: there is no reliable iowait statistics in Linux. This is only truth. From PROC(5) we read:
iowait (since Linux 2.5.41)
(5) Time waiting for I/O to complete. This value is not reliable, for
the following reasons:
The CPU will not wait for I/O to complete; iowait is the time that a task is waiting for I/O to complete. When a CPU goes into idle
state for outstanding task I/O, another task will be scheduled on this
CPU.
On a multi-core CPU, the task waiting for I/O to complete is not running on any CPU, so the iowait of each CPU is difficult to
calculate.
The value in this field may decrease in certain conditions.
So, my suggestion for is to forget about iowait measurements in Linux.
answered Aug 21 at 10:42
Bob
72017
add a comment |Â
up vote
0
down vote
up vote
0
down vote
Allow me to reveal the small Linux secret: there is no reliable iowait statistics in Linux. This is only truth. From PROC(5) we read:
iowait (since Linux 2.5.41)
(5) Time waiting for I/O to complete. This value is not reliable, for
the following reasons:
The CPU will not wait for I/O to complete; iowait is the time that a task is waiting for I/O to complete. When a CPU goes into idle
state for outstanding task I/O, another task will be scheduled on this
CPU.
On a multi-core CPU, the task waiting for I/O to complete is not running on any CPU, so the iowait of each CPU is difficult to
calculate.
The value in this field may decrease in certain conditions.
So, my suggestion for is to forget about iowait measurements in Linux.
answered Aug 21 at 10:42
Bob
72017
Allow me to reveal the small Linux secret: there is no reliable iowait statistics in Linux. This is only truth. From PROC(5) we read:
iowait (since Linux 2.5.41)
(5) Time waiting for I/O to complete. This value is not reliable, for
the following reasons:
The CPU will not wait for I/O to complete; iowait is the time that a task is waiting for I/O to complete. When a CPU goes into idle
state for outstanding task I/O, another task will be scheduled on this
CPU.
On a multi-core CPU, the task waiting for I/O to complete is not running on any CPU, so the iowait of each CPU is difficult to
calculate.
The value in this field may decrease in certain conditions.
So, my suggestion for is to forget about iowait measurements in Linux.
answered Aug 21 at 10:42
Bob
72017
edited Aug 21 at 10:59
answered Aug 21 at 10:42
Bob
72017
answered Aug 21 at 10:42
Bob
72017
answered Aug 21 at 10:42
Bob
72017
72017
add a comment |Â
add a comment |Â
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1
Could you please provide physical disk model?
ls /dev/disk/by-id/or something. Honestly, I haven't heard of a disk with cores and I am very curious.– mikst
Aug 21 at 9:36
Sorry, I rectified the mistake, the server has 12 cores.
– M. Rafi
Aug 21 at 9:48