The iowait tag has no wiki summary.
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IO-intensive processes hang with iowait, but no activity going on
I have a bunch of IO-intensive jobs, and to boost performance, I just installed two SSDs in a compute server, one as a scratch file system, one as swap. After running for some time, all my processes ...
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1answer
47 views
How can i view the disk latency of a ZFS pool, or of the disks in it?
I'm using FreeBSD. I would like to write a munin plugin to log it, but i don't understand how to get this data.
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1answer
62 views
How to combine different pidstat outputs (CPU, I/O, Disk Usage)
I would like to use pidstat to get both -u, -r and -d flags. Is there a way to do so?
The idea, is to get both CPU, I/O and disk usage.
Cheers
Ps. Combining the flags as -urd doesn't work in Ubuntu ...
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4answers
747 views
High iowait on Amazon EC2 MySQL instance with EBS volume
We have a MySQL server running on an Amazon EC2 c1.medium instance relying on a single EBS volume using the ext3 filesystem for storage.
This MySQL server is queried ~500/ps by several applications ...
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3answers
186 views
MySQL on ubuntu very high IOWAIT
Can anyone advice what is going on with my setup.
I have mysql server on ubuntu which periodically produce very high iowait.
for long time up to 10-20 minutes.
During this time system and database ...
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0answers
186 views
MySQL INSERT … SELECT renders server unresponsive
Solution: Although I haven't found a proper solution yet I'm at least sure that this is purely a disk I/O problem and has nothing to do with MySQL...
I have a MySQL server (5.1.54-1ubuntu4-log) ...
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2answers
433 views
What iowait values are ok?
I am trying to find the bottleneck of a server running a fairly busy php/mysql site. My first culprit was io but iostat shows that on average iowait consumes only %3.60 of cpu time. here is the ...
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2answers
344 views
mysqld causing machine to lockup with high iowait
I've inherited a LAMP server running centos, which randomly hangs from time to time despite low web traffic.
I've installed Server Density to monitor what's going on, and have found during a hang the ...
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3answers
342 views
JVM hangs with 100 IO wait on Ubuntu Maverick (AWS EC2 xlarge instance)
Asked this question on on stackoverflow, reposting:
Have an xlarge instance in AWS running 9 Tomcats with heaps from 256M to 4G. With Ubuntu 10.04 the box sporadically hangs for a few hours with huge ...
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4answers
4k views
How to measure IOwait per device?
I have a server, which exports home directories over NFS. They are on software RAID1 (/dev/sdb and /dev/sdc) and the OS is on /dev/sda. I noticed that my %iowait as reported by top and sar are ...
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2answers
245 views
How do I know if my disks are being hit with too many I/O reads or writes or both?
I know a bit about disk I/O and bottlenecks relating to this especially when relating to databases.
How do I really know what the max I/O numbers will be for my disks? What metric might be available ...
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1answer
76 views
High IOWait executing JBoss 3.2.7
Server Details:
Kernel: Linux wiq31 2.4.21-9.ELsmp #1 SMP Thu Jan 8 17:08:56 EST 2004 i686 i686 i386 GNU/Linux
CPU: 4 x Intel(R) Xeon(TM) CPU 3.06GHz
Memory: 1028520 kB
JBoss version: 3.2.7
Every ...
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3answers
754 views
100% iowait + drive faults in dmesg
I have a server on which resides a fairly visited web app.
It has a raid1 of 2 HDDs, 64MB Buffer, 7200 RPM.
Today it started throwing out errors like:
kernel: ata2.00: exception Emask 0x0 SAct ...
2
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1answer
5k views
is CPU actually occupied during iowait (%wa in top) on Linux / EC2?
On an 8-way Amazon EC2 instance (running Linux 2.6.21) with 8 EBS volumes and a lot of disk traffic, we see high %wa in top (30-40%), and high load average (8-9). My understanding is that processes ...
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2answers
4k views
Finding the root cause of 100% iowait in Linux
I have a system that is a few years old that is running Fedora 7 (I know, it's old too).
Now I have PS3 Media Server running (and some other things, like Vmware and Plone) and I noticed that I was ...
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2answers
2k views
Does iowait include time waiting for network calls?
The proc(5) manpage describes iowait as "time waiting for IO to complete". This was mostly explained in an earlier question. My question is: while waiting in blocking IO, does this include waiting on ...
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4answers
7k views
Can anyone explain precisely what IOWait is?
As much as I have read about iowait, it is still mystery to me.
I know it's the time spent by the CPU waiting for a IO operations to complete, but what kind of IO operations precisely? What I am also ...
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4answers
2k views
Resolving high iowait on Samba server
We've got a centralised file cache which a cluster of web servers use to store "heavyweight" pages. Each webserver uses Samba to mount this shared area.
We're getting a lot of iowait on the server, ...
