IO (or I/O) is an abbreviation for input/output.

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Are networks now faster than disks?

This is a software design question I used to work on the following rule for speed cache memory > memory > disk > network With each step being 5-10 times the previous step (e.g. cache ...
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4answers
9k views

Determine what's causing high disk IO

I'm having a problem with my VPS and disk IO. My server is running nginx + PHP-FPM + APC. The database is located on another dedicated VPS. I have several Wordpress MU sites living on the web server. ...
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2answers
987 views

High Disk I/O rate. How to investigate

One of my servers is getting very high Disk I/Os. The problem is that the disk I/Os are constantly increasing. The server just have simple LAMP configuration and there shouldnt be any disk operation ...
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4answers
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Measuring 'total bytes written' under Linux

We're quite interested in exploring the possibility of using SSD drives in a server environment. However, one thing that we need to establish is expected drive longevity. According to this article ...
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3answers
2k views

High Load - Low IO - Low CPU usage

I have a system whose load is rather high. As you can see from the top output below, CPU usage and I/O is negligible: top - 17:31:59 up 4 days, 2:34, 2 users, load average: 1.00, 0.99, 1.00 ...
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2answers
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VMWare Esxi Looking for Bottlenecks

I have a VMWare ESxi box, 22GB ram, Dual Quad Core Xeon, 2 Sas drives + Write caching raid controller etc. Anyways, have about 30 small XP VM's running on it and starting to get some very slow boot ...
0
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3answers
525 views

How to view formatted iotop log file in terminal with a cat

Hey there. So I have logged the history of Disk usage with a iotop > iohis.log How can I view the file so it is formatted nicely and I can actually find the issue. I thought I could use the cat but ...
0
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3answers
221 views

Estimate daily network IO between 2 servers

I have 2 servers : a database server (SQL Server 2008, called server A) and an application server (called server B) which send SQL queries to the first one. They are actually in the same LAN, but we ...
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2answers
318 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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6answers
17k views

I/O Performance Benchmarking Linux

Just finished setting up a poor mans SAN with iSCSI and want to benchmark it. What are some good I/O performance benchmarks for Linux besides: hdparm -tT /dev/sda1 How do I get a IOPS measurement? ...
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1answer
545 views

IO-related lockups on a Xen PV guest running Ubuntu 10.04

I have a Xen PV guest, running Ubuntu 10.04. I do not run the underlying host. Kernel is the stock one provided by Ubuntu: Linux nephos 2.6.32-21-server #32-Ubuntu SMP Fri Apr 16 09:17:34 UTC 2010 ...
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1answer
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Determining which process is causing heavy disk I/O?

I've seen this question: How to identify heavy write to disk? And I've used dstat and atop before...but they don't seem to pinpoint what process is causing disk I/O. For example, from dstat: dstat ...
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2answers
3k views

Will adding a SSD cache device to my ZFS storage improve performance?

The server has 4GB of RAM and my zpool is made up of 15.5k SAS drives arranged like this: NAME STATE READ WRITE CKSUM tank ONLINE 0 0 0 raidz1-0 ...
0
votes
1answer
388 views

Can I set noatime for my XEN guest OS partition? Will it work?

I have a VPS in cloud environment based on XEN Virtualization platform. /etc/fstab looks like that: LABEL=PRGMRDISK1 / ext3 errors=remount-ro 0 0 As far as I know IO can pretty ...
3
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7answers
5k views

How do I tell which processes are writing heavily to disk in CentOS 5?

Our server started getting slow, so I ran iostat on it. iostat -dx 5 Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 0.00 ...
6
votes
4answers
238 views

Frequently accessed files and I/O usage

I'm curious, from a performance standpoint, is there an advantage in storing all files in one directory versus having each file in a separate directory? I'm not concerned about organization. Also, ...
0
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2answers
151 views

What types of IO does SQL trace display?

Are they physical or logical IOs? If they're logical, is there a way to break it out similar to STATISTICS IO for a production server?
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1answer
1k views

Linux Read-Ahead Downsides

Hope all is well. I have a question regarding read-ahead caching. Are there any downsides to raising the size of the read-ahead cache? On our farm, we're currently running at 256, and upon raising ...
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2answers
1k views

Windows Disk I/O Analysis

It appears that we are having a problem with the disk i/o speed on our Windows 2003 Enterprise Edition server (64-bit). As we were initializing a database that created two 1G tablespaces on 3 ...
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1answer
3k views

Debugging IO Limitation

I have a Fedora box with some severe IO limitations which I have no idea how to debug. The server has a Areca Technology Corp. ARC-1130 12-Port PCI-X to SATA RAID Controller with 12 7200 RPM 1.5 TB ...
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2answers
525 views

I/O Reads and Writes per process Unix/SunOS?

Can prstat or something similar tell me how many reads/writes a process is doing similar to how Task Manager on Windows can show I/O Reads, I/O Writes and many other I/O columns per process? I'm ...
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2answers
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lsass.exe high I/O with SQL Server 2005 sp3

Hi I have a SQL Server 2005 Enterprise Edition on a Windows Server 2003 Enterprise sp2. Lately, I get very high I/O(Reda, Write, Other in Task Manager) from process lsass.exe. When I run sysinternals' ...
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5answers
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How to identify heavy write to disk?

I have this problem with server running CakePHP application. The server is insanely slow, I first thought that it's application problem, but then I found constant 5-6MB/s write to disk. What is the ...
0
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2answers
4k views

CPU or network I/O bound?

I'm trying to find out whether my server is network IO bound or CPU bound. I did look at the output of some of the typical tools to check the current status of the system (output of iostat, sar and ...
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3answers
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Linux - How can I see what's waiting for disk IO

I have a server that has a really high load. Nothing is jumping out at me in terms of CPU usage, and it's not swapping. I think it's cause some processes are waiting for disk IO, and I want to see ...
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2answers
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How can I monitor network I/O usage per process under Linux?

Such known tools like iftop/iptraf display network I/O per interface and per connection. Is there a way to see network I/O statistics per process?
2
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1answer
316 views

How to track cause of blocking IO problems

I move between multiple subnets and networks on a regular basis. I'm often faced with Explorer and other programs that stall in what appears to be an IO request. I'm trying to find a consistent way ...
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5answers
647 views

Expected throughput when re-building RAID array?

I'm just doing some testing on a NAS RAID array we've been lent to see if we want to deploy it. Just to see whats what, I decided to see what kind of network performance we get when it's re-building a ...
0
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4answers
270 views

Exchange 2003 I/O Troubles

We have some internal processes that send email to our Exchange 2003 system (on Win2K3 R2 32bit). Recently they have been intermittently failing with various errors -- boiled down they report ...
57
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7answers
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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 ...
15
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4answers
18k views

How to identify I/O bottlenecks on a Linux server?

How do you determine that the performance of your Linux server is I/O bound and, perhaps more importantly, what process or processes are casuing the problem?