IO (or I/O) is an abbreviation for input/output, most commonly referring to disk input/output.

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High disk I/O activity in CentOS server

I have about 16 websites in a CentOS dedicated, and I am having some problems on high traffic hours, it seems to be a high disk I/O activity causing a general slowdown. I've installed atop and this ...
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iostat shows 100% utilization - what can be done to improve performance?

I have dedicated web server with CentOS. Recently, I get very high server load, probably caused due to IO bottleneck. iostat -mx 3 shows: avg-cpu: %user %nice %system %iowait %steal %idle ...
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Beyond 1Gb upload on a single linux server

I have a high hit nginx web server on CentOS that provides static large content. when the number concurrent connection are low, server could easily provide up to 4Gb of traffic , but when the number ...
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1answer
301 views

iotop does not show writes

What could be writing on the disk that iotop does not show? # iotop -a Total DISK READ: 8.19 M/s | Total ****DISK WRITE: 3.34 M/s**** TID PRIO USER DISK READ DISK WRITE> SWAPIN IO ...
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208 views

Linux buffer memory always stays at zero

One of my hosted server is a Xen guest running Debian and linux kernel 2.6.32 then 2.6.38. It has been running fine for quite some time (more than a year) but I recently noticed something weird. For ...
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247 views

How can I determine the specific file referenced by fs_usage, which is listed by block

I was investigating a problem on a Mac OS X 10.6.8 Server, where users were complaining of access slowdowns. Network throughput slowed to a crawl. It felt like the server was overburdened. System ...
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1answer
228 views

inonice not working properly in xen dom0

I have a Xen Dom0 (3.2) with a bunch of domUs (paravirt). DomU VBDs are on local LVM volumes. Now I want to get backups of the LVM volumes using snapshots. I use rsync ioniced to idle (ionice -c3). I ...
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209 views

Does DFS-R actually write 100%+change to a file on the receiving server(s)?

I am analyzing DFS-R on Windows 2003 R2 and have come across a horrendous thing. It appears that when you append a small amount of data to a large (existing) file, the write cost on the server for ...
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58 views

how to find cause of io spike

Everyday at around the same time, the IO usage on the server where our mysql slave goes up to 100%. I have setup a script that takes IO information every five minutes so I can find out why this ...
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781 views

Linux - KVM - very slow disk io

The I/O performance of my new server is pretty low. I Googled and tried everything I can imagine. First of all, here are the Hardware Components: AMD Opteron(tm) Processor 6344 4x Seagate ...
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htcacheclean doesn't seem to be cleaning the cache

I'm running mod_cache with apache 2 on a fairly high traffic'd site. I've set the htcacheclean to run in demon mode every 10 minutes to keep the cache at 4GB. It's currently at 15GB and doesn't seem ...
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76 views

How can I see which devices are used by a process?

iotop and iostat are great tools to see how much I/O is happening. But I haven't found out how these (or other) tools can show me the I/O rate per device and per process. So I'm looking for a way to ...
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43 views

File transfer slows down the server response

We are on Win server 2003 and we transfer the files across the same intranet either using CuteFTP or through mapped drives. The problem here is the file transfers start fast and get slower as time ...
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1answer
361 views

High cancelled_write_bytes, high IO load, concurrent memory-mapping

I have a software for persisting/retrieving data from files (a bit like database, but it's not exactly a database engine). It's not open source and the documentation is sparse, therefore I don't have ...
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1answer
137 views

replacement drive cage for power edge R710

Hi I'm performance tuning a DB server its a Dell R710 there is a very significant I/O bottleneck. Unfortunately the server was purchased with the 6 x 3.5 inch sata configuration which doesn't give me ...
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1answer
167 views

Sendmail greatly increases value of Total DISK WRITE

Sendmail is installed on the server. It sends an average of 6 emails at 3K per second and writes 18 files in /var/spool/mqueue-client. Because of this high disk writes iotop: Total DISK WRITE: ...
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Benchmarking for DISK I/O Writes Per Second - ElasticSearch and MySQL

During working on our project we needed to decide should we use "ElasticSearch" or "MySQL" to record the audit/trail logs of the system. Searching speed is not an issue here, we needed to see the disk ...
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313 views

kworker consuming +90% IO and zero disk write

this is a standard apache web server on AWS Linux AMI + EBS. We are noticing high load average (+8) and iotop -a shows: Total DISK READ: 0.00 B/s | Total DISK WRITE: 2.37 M/s TID PRIO USER ...
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VPS Unknown Read/Write

I had an lfd email alert - I have installed CSF - today revealing that my server (Centos 6.6) has been using a lot of server resources for 5 minutes. I checked my VPS graphs and noticed that my ...
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“Nosy Neighbor” and the CFQ scheduler

I'm trying to understand how does using CFQ affects the "Nosy Neighbor" problem. I'll ask it a bit naively, can a "Nosy Neighbor" even exist when using CFQ? Isn't that CFQ should make sure all ...
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288 views

How can I optimize the Windows file cache so flushing a file is faster?

I have a third-party, object-oriented database server running on a Windows Server 2003 x64 machine with 24 GB of RAM. Except for some system processes and monitoring tools, the database server is the ...
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Restrict I/O Write usage using cgroups

I am trying to restrict I/O write usage on my server using cgroups. Here is my partition table info: major minor #blocks name 8 0 10485760 sda 8 1 9437184 sda1 8 ...
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__ticket_spinlock high cpu

We are having a strange problem on our Ubuntu 10.04 KVM infrastructure, where periodically, one of two vm webservers freaks out, with persistently high load, even if we restart the applications. (the ...
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476 views

Why are pgpgin/s and majflt/s inconsistent in sar -B?

In sar -B ouptut, I would naively expect pgpgin/s to equal majflt/s multiplied by the system page size. From man sar: pgpgin/s Total number of kilobytes the system paged in ...
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193 views

Visualizing IO other then seekwatcher

Is there any other programs that can generate visuals/graphs/diagrams (movie and pictures) to visualize IO across a full device other then seekwatcher? NOTE: seekwatcher generates visuals(pic/movie) ...
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239 views

Reason for high CPU time when executing fio

After weeks of troubleshooting some performance issues I have on my VPS running Ubuntu 12.04 LTS, I am getting closer to the conclusion that the problem is related to IO. When I have a considerable ...
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File I/O Throughput

I have an IBM x3650 M4 server (64-bit) running Ubuntu 13.04 Desktop (32-bit). I realize that this is a non-standard setup by it's being driven by other requirements. I am seeing slow file writes ...
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49 views

Chrooted from LiveCD: Bad IO performace

my Ubuntu Server installation is broken, so I grabbed a Ubuntu Desktop CD, mounted my Ubuntu installtion on my hard disk and chrooted into it. But now my IO performance is really bad: # time dd ...
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516 views

I/O error on non-existent device?

Getting the following in /var/log/messages: Sep 17 10:38:53 server1 kernel: end_request: I/O error, dev sde, sector 0 Sep 17 10:38:53 server1 kernel: end_request: I/O error, dev sde, sector 63 Sep 17 ...
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521 views

Heavy disk write on a Debian VPS gives “ata1: lost interrupt (Status 0x50)”

I have a new Debian VPS that appears to fail almost every time I run a heavy disk write test on ext4 filesystem. The filesystem goes to read-only mode and "ata1: lost interrupt (Status 0x50)" is ...
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33 views

How efficient is the tac command on large files

The taccommand (catreversed) can be used to read a file backwards, just like cat reads it rom the beginning. I wonder, how efficient this is. Does it have to read the whole file from the beginning and ...
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MongoDB hogging IO but it doesn't show in mongotop or mongostat

Iotop says mongod is using a lot of IO (96.32%) for a long while but mongotop and mongostat show a bunch of zeros. How can I better monitor mongodb and find out what's happening?
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IO Rate is exceedingly incrementing

I have read through Is a 'high' IO rate healthy?, and was at ease when I read someone say that even 50,000 / hr wasn't an issue.... or not unhealthy, to answer their question; so I increased ...
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Can poor Internet connection affect the IO read on my server?

I'm trying to spot the culprit causing too much IO read in my server. Issuing IOTOP -ao I have come accross many httpd processes among which one caught my attention: PRIO USER DISK READ ...
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BUG: soft lockup - CPU#0 stuck for 23s! on XEN PV debian related to high i/o load

i am currently experiencing some problems with my Debian Xen System. It runns on an old opteron System with two Dual Core AMD Opteron(tm) Processor 275 CPUs. I am using image files (block devices) ...
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freebsd: disk i/o utilization statistic by user

Whether there some utils for collect/view statistic about disk I/O utilization by user in FreeBSD? After googling that question i found only sa, but in its manpage is not any information about ...
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666 views

Direct I/O on Linux

I'm trying to enable Direct I/O on /opt (/dev/sda6, ext4) on Linux Mint 13. What I'm trying is: mount -o dio,rw /dev/sda6 /opt as root. The system responds with: mount: wrong fs type, bad ...
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535 views

High disk usage in CSRSS.EXE

I recently started working on the server for a certain software (Tango). The users complained that it recently became extremely low, so I used an application (ProcessHacker) to see the resource usage ...
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81 views

Two servers with inconsistent disk speed

I have two servers of identical spec (bought at the same time), except for the drive configuration: Server A: C: and D: drives are partitions on the same 2 disk RAID 1 E: is a 2 disk RAID 0 ...
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Windows server 2008 I/O counters

For an I/O capacity study I'm working on, (on a windows server 2008R2 system) I'd like to gather absolute I/O counts for a given physical (or logical) disk over a specific period of time. When I look ...