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ashley75 02-06-2006 04:06 PM

Iowait
 
Hi all,

below is the result from top on my server:

14:49:51 up 39 days, 17 min, 3 users, load average: 1.34, 1.27, 1.63
326 processes: 325 sleeping, 1 running, 0 zombie, 0 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 2.8% 0.2% 0.9% 0.1% 0.6% 51.6% 43.5%
cpu00 5.4% 0.4% 1.4% 0.4% 1.0% 61.0% 30.3%
cpu01 4.4% 0.0% 1.4% 0.0% 0.8% 61.6% 31.6%
cpu02 1.2% 0.4% 0.6% 0.0% 0.6% 41.6% 55.6%
cpu03 0.2% 0.0% 0.4% 0.0% 0.2% 42.6% 56.6%



as you see, iowait is is about 50%, what does it tell you??? I noticed that the server running bit slow and I am new to Linux.

thanks,

Tinkster 02-06-2006 04:40 PM

It tells us that you forgot to post the next ten lines of your
tops output, and that you failed to give any detail about the
machines physical details, e.g. HDD subsystem, network cards, ...


Cheers,
Tink

ashley75 02-06-2006 05:08 PM

Sorry Tink

16:00:21 up 39 days, 1:27, 5 users, load average: 9.10, 8.74, 8.16
366 processes: 364 sleeping, 2 running, 0 zombie, 0 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 16.6% 0.0% 3.3% 0.0% 0.0% 79.7% 0.0%
cpu00 15.4% 0.2% 3.2% 0.0% 0.0% 81.2% 0.0%
cpu01 17.1% 0.0% 3.3% 0.3% 0.1% 78.8% 0.0%
cpu02 13.9% 0.0% 3.7% 0.0% 0.0% 82.2% 0.0%
cpu03 19.9% 0.1% 2.9% 0.0% 0.1% 76.6% 0.0%
Mem: 4091528k av, 4072000k used, 19528k free, 0k shrd, 23380k buff
2835480k actv, 744224k in_d, 76576k in_c
Swap: 3068372k av, 698784k used, 2369588k free 3297556k cached

PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND
13377 oracle 16 0 51640 49M 48368 S 4.5 1.2 0:01 2 oracle
13399 oracle 16 0 89196 85M 82816 S 3.8 2.1 0:02 2 oracle
13394 oracle 15 0 84820 81M 80488 D 3.7 2.0 0:01 0 oracle
12885 oracle 15 0 145M 123M 98868 D 1.4 3.0 1:56 1 oracle
13413 oracle 23 0 26888 24M 20604 R 0.3 0.6 0:00 3 oracle
13388 oracle 15 0 27940 23M 22684 S 0.2 0.5 0:00 1 oracle
11 root 15 0 0 0 0 SW 0.1 0.0 38:27 3 kswapd
5024 oracle 25 10 10556 8312 2784 S N 0.1 0.2 363:18 3 rhn-applet-gui
13261 oracle 16 0 1408 1408 904 R 0.1 0.0 0:02 0 top
13403 oracle 23 0 10872 10M 9300 S 0.1 0.2 0:00 2 oracle
13405 oracle 23 0 10904 10M 9332 S 0.1 0.2 0:00 0 oracle
13409 oracle 23 0 10936 10M 9364 S 0.1 0.2 0:00 2 oracle
13411 oracle 23 0 10880 10M 9308 S 0.1 0.2 0:00 0 oracle
1 root 15 0 300 264 236 S 0.0 0.0 0:36 0 init
2 root RT 0 0 0 0 SW 0.0 0.0 0:00 0 migration/0
3 root RT 0 0 0 0 SW 0.0 0.0 0:00 1 migration/1
4 root RT 0 0 0 0 SW 0.0 0.0 0:00 2 migration/2
5 root RT 0 0 0 0 SW 0.0 0.0 0:00 3 migration/3
6 root 15 0 0 0 0 SW 0.0 0.0 0:00 2 keventd
7 root 34 19 0 0 0 SWN 0.0 0.0 0:00 0 ksoftirqd/0
8 root 34 19 0 0 0 SWN 0.0 0.0 0:00 1 ksoftirqd/1
9 root 34 19 0 0 0 SWN 0.0 0.0 0:00 2 ksoftirqd/2
10 root 34 19 0 0 0 SWN 0.0 0.0 0:00 3 ksoftirqd/3

Tinkster 02-06-2006 05:53 PM

And the disk-subsystem on the machine is ... ?
Who or what is it talking to in terms of networking, are you
running an (or several) app-servers against it?
More than one network card? What speeds?


Cheers,
Tink

ashley75 02-06-2006 09:32 PM

I don't have any app running on this server, I just have 15 databases running and couple users are connecting to them concurrently, this machine is fairly new with dual Xeon processor, the IOWAIT are at peak almost al the time so I am trying to find out what is happening.

Please throw out some advises

Tinkster 02-06-2006 09:46 PM

And the disk-subsystem is?
And what Oracle version are you running?
How do the users connect, running plain old sqlplus against it?
And why do you always only ever answer one of my questions
ignoring the rest?
How am I supposed to help when you don't answer the others? :}



Cheers,
Tink

ashley75 02-06-2006 10:14 PM

Sorry, I didn't mean to ignore your question, I just don't understand what you mean since I am very sufficient with Linux.

And the disk-subsystem is?
how do you find out about this

And what Oracle version are you running?
Oracle 10G release 2

How do the users connect, running plain old sqlplus against it?
I don't know at this points. At this point, I am still looking for who/which datababse drag the system down


If you don't ming to let me know how to narrow down and troubleshoot the problem, that would be greatly appreciated. Like right now is off business hours and the iostat still hight.

Tinkster 02-06-2006 10:50 PM

Quote:

Originally Posted by ashley75
Sorry, I didn't mean to ignore your question, I just don't understand what you mean since I am very sufficient with Linux.

And the disk-subsystem is?
how do you find out about this

If you're the sys-admin you should know off the top of your head :}
Have a look at the output of
fdisk -l
and we'll (try to) tackle it from there.

Quote:

Originally Posted by ashley75
And what Oracle version are you running?
Oracle 10G release 2

15 DBs on a machine with only 4GB RAM?
Hope they're not too big/busy.
What kind of app is Oracle being used for? Have you configured
opmn and emctl for those databases?


Quote:

Originally Posted by ashley75
How do the users connect, running plain old sqlplus against it?
I don't know at this points. At this point, I am still looking for who/which datababse drag the system down

How can you if you don't know what's happening?


Quote:

Originally Posted by ashley75
If you don't ming to let me know how to narrow down and troubleshoot the problem, that would be greatly appreciated. Like right now is off business hours and the iostat still hight.

Chances are that the machine is busy paging stuff in and out.



Cheers,
Tink

ashley75 02-07-2006 09:29 PM

Tink,

thanks so much for your advises and now I found out I don't have fdisk functionality neither iostat on my server so the next question is what package do I need to install so I can those two utilities loaded on my server.

thanks a bunch

Tinkster 02-07-2006 10:14 PM

The machine is a DeadRat box?

sysstat
and
util-linux

ashley75 02-09-2006 04:32 PM

thanks Tink,

I got fdisk and iostat installed. now the next question is "the gzip command really take a lot of resources???"

Please see the below when I have gzip running:


avg-cpu: %user %nice %sys %iowait %idle
21.00 0.00 1.13 60.30 17.57

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sda 182.05 1.60 5361.69 16 53456
sda1 0.00 0.00 0.00 0 0
sda2 0.00 0.00 0.00 0 0
sda3 182.05 1.60 5361.69 16 53456
sda4 0.00 0.00 0.00 0 0
sda5 0.00 0.00 0.00 0 0
sda6 0.00 0.00 0.00 0 0
sdb 350.95 9098.50 3792.98 90712 37816
sdb1 350.95 9098.50 3792.98 90712 37816



AFTER GZIP is completed:

avg-cpu: %user %nice %sys %iowait %idle
0.18 0.00 0.18 9.05 90.60

Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sda 33.30 3.21 516.75 32 5152
sda1 0.00 0.00 0.00 0 0
sda2 0.00 0.00 0.00 0 0
sda3 33.30 3.21 516.75 32 5152
sda4 0.00 0.00 0.00 0 0
sda5 0.00 0.00 0.00 0 0
sda6 0.00 0.00 0.00 0 0
sdb 1.40 1.60 28.08 16 280
sdb1 1.40 1.60 28.08 16 280




Is it normal for gzip to behave this way??? would you recommend to use some other utility to compress??? or you think I have I/O issue on my server???

thanks

Tinkster 02-09-2006 05:43 PM

Could you please put code-tags around the stuff you copy & paste
to make it more readable? Zip should be fine, other compression
methods would a) use more CPU or b) be inefficient at compression,
there's just a lot of I/O going on.

Can you give me details about the hardware we're looking at?
Server type, CPU speed, controller type ... and again: if the
box is a RedHat machine make sure you have turned auditing off,
otherwise it will be happily playing with itself. The auditing
is something you may want on a file-server, but definitely NOT
on a database machine.

And once again: it would be nice if you provided more detail
in the first place, e.g which distro and version you're using ;)

For future reference, and to make both your and our lives with
helping you easier, read this, please



Cheers,
Tink

jlliagre 02-09-2006 06:41 PM

Quote:

Originally Posted by ashley75
thanks Tink,

I got fdisk and iostat installed. now the next question is "the gzip command really take a lot of resources???"

Please see the below when I have gzip running:

...

Is it normal for gzip to behave this way??? would you recommend to use some other utility to compress??? or you think I have I/O issue on my server???

What are the numbers that lead you to believe there is a ressource issue on your system ?

Tinkster 02-09-2006 06:50 PM

Quote:

Code:

CPU states: cpu  user  nice  system    irq softirq iowait idle
total            16.6%  0.0%    3.3%    0.0%    0.0%  79.7% 0.0%


Quote:

Code:

avg-cpu:  %user  %nice    %sys  %iowait  %idle
          21.00    0.00    1.13    60.30  17.57


I think this is what she's refering to ...


Cheers,
Tink

jlliagre 02-09-2006 08:14 PM

iowait is really just CPU idle time.

Switching to a faster algorithms wouldn't probably improve significantly the process, as this gzip operation seems I/O bound.

sda3 and sdb1 are busy, looks fine to me, unless the I/Os are not on behalf the zip operation, but a consequence of memory shortage and pagination.


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