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

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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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190 views

Why is my synchronized I/O so bad compared to direct?

I have two 3TB disks in a software RAID 1 setup and the host OS is 64bit Debian wheezy. Issuing: dd if=/dev/zero of=test bs=64k count=3k oflag=direct && rm test Yields: 201326592 bytes ...
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3answers
3k views

High await in sar

My database server has the following sar output for the data device: [postgres@dbsrv07 ~]$ LC_ALL=POSIX sar -d |egrep "await|dev253-2" 00:00:01 DEV tps rd_sec/s wr_sec/s avgrq-sz ...
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2k views

debian Read-only file system error

I logged on to my debian box and tried running some commands and I was presented with the following message. sudo: Can't open /var/lib/sudo/username/0: Read-only file system After doing some ...
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2answers
351 views

VMWare ESXi: to extend a partition or create a new drive?

Is it better to extend an existing partition or to create a new drive in a VMWare ESXi virtual machine? I'll be using LVM to put the drive in an existing volume group on my VM and to extend a SAN ...
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1answer
438 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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57 views

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 ...
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270 views

Strange IO issue with Ubuntu 12.04

I have a very strange IO issue with Ubuntu 12.04 and MySQL. Currently the machine is only a replicated slave with an occasional read query hitting it. The disk utilization spikes randomly and ...
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3answers
121 views

Running a process within a limited amount of resources, in Linux

Is there a way to run a process (e.g. ls, du, find .. etc) within a strictly limited amount of resources (i.e. cpu, memory, I/O) aside from using nice & ionice, as I didn't find them effective ...
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2answers
400 views

whats the difference between 1lane and 2lane with SATA-3 speeds? [closed]

I read the beauty of PCIe is that a designer can combine two, four, eight or sixteen of PCIe lanes into a single data port. 2.5 Gb/s PCIe×1 5 Gb/s PCIe×2 I have two sata 3 drives that I want to ...
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371 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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100 views

Detect file update from modification time

Is there a way to see how often a file is being updated? I mean I need to see if the modification time of a file is updated in a dynamic way (same as tail shows if the file is updated in a dynamic ...
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1answer
399 views

Why is autovacuum using so much IO when running on a partition's master table after upgrading PosgreSQL from 8.4 to 9.1?

We have an application where we are collecting timestamp-based data. Since a month of data goes over 30M rows (and growing each month), we decided to partition the data on an year-and-month basis. We ...
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4answers
7k views

Flush-0:n processes causing massive bottleneck

I have a LAMP cluster that shares files via NFS and occasionally one of them will be stricken for a while when mysterious flush processes start appearing. Can anyone help me? The only way to resolve ...
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56 views

High load cause? [duplicate]

Possible Duplicate: what is my server high load cause (4 cores and 8 thread cpu) What is my high load cause? CPU,RAM or IO? 4 Core, 8 thread cpu top - 22:27:07 up 149 days, 5:26, 1 ...
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1answer
2k views

Poor guest I/O performance KVM Ubuntu 12.04

I have a guest VM running inside a 12.04 Ubuntu host. VM was created using the vmbuilder python script. On the host the phoronix-test-suite "aio-stress" gives a performance speed of >1600MB/s Random ...
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1answer
424 views

Limited I/O Performance in Dell T410

We have a small number of Dell T410 and T710 systems. Each has a Dell SAS 6iR controller with 6 SATAII disks, 1x160GB OS and 5x3TB DATA disks. We have been having disk access speed issues all ...
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1answer
482 views

Poor KVM guest IO performances

I've a DOM0 packed with two 3TB hard drives configured as a software RAID1, also sporting 16GB of memory. The DOM0's Linux distro is a CentOS 6.3 and the hypervisor is a libvirt-managed KVM. I'm ...
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6k views

jbd2/dm-0-8 consuming all I/O

What is jbd2/dm-0-8 and why It is consuming all my I/O usage and causing I/O wait? Is there anyway to disable this? Bonnie++ results: http://pastebin.com/iQCWP1qp $ sudo hdparm -t /dev/sda1 ...
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4answers
739 views

what is my server high load cause (4 cores and 8 thread cpu)

What should i do if I want to prevent this high load. My website becomes slow when load is higher than 8. Please see iotop result too. top - 20:23:10 up 127 days, 3:22, 1 user, load average: ...
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1answer
563 views

Identify which process is responsible for heavy disk i/o under FreeBSD

I wonder how I can monitor which process takes out all my IO bandwith. The only command i know is gstat but it shows cumulative info. Is there any tools i can use to inspect the running processes for ...
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3answers
962 views

Disk write speed much slower than read speed

I have a VPS server (WiredTree), running CentOS. After experiencing some performance issues I created a simple benchmark for disk read/write speed using the following script: echo Write to disk dd ...
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1answer
243 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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2answers
2k views

Reduce the I/O priority of Windows Backup (Windows Server 2008 R2)

I have a PostgreSQL running on Windows Server 2008 R2 x64 box. And I have scheduled a backup everyday from the RAID 1 DB disk to a dedicated standalone disk. They are SAS 15k on Dell PERC 6i. I am ...
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4k views

Determining cause of high NFS/IO utilization without iotop

I have a server that is doing an NFSv4 export for user's home directories. There are roughly 25 users (mostly developers/analysts) and about 40 servers mounting the home directory export. ...
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1answer
620 views

Quantifying the effects of partition mis-alignment

I'm experiencing some significant performance issues on an NFS server. I've been reading up a bit on partition alignment, and I think I have my partitions mis-aligned. I can't find anything that ...
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2answers
4k views

Issues with Server 2012 using DFSR running on Hyper-V 2012

We have a number of Server 2012 systems, all of which run virtualised on Hyper-V 2012 server. We are having problems with two such virtual instances, both of which are used as file servers, whereby ...
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1answer
2k views

Strange high CPU I/O wait on postgresql server

I'm really struggling with a performance issue currently, where all my database queries takes up to a 1000 times more than normally, when my database server is under "heavy" load. I have a server ...
5
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1answer
2k views

High I/O latency with software RAID, LUKS encrypted and LVM partitioned KVM setup

I found out a performance problems with a Mumble server, which I described in a previous question are caused by an I/O latency problem of unknown origin. As I have no idea what is causing this and how ...
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3answers
4k views

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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213 views

Does php function move_uploaded_file() cause disk io?

The /tmp dir and the destination dirs are on the same file system. If its handling large files (over 1GB), does this create any overhead in term of disk io? Would it be better to simply have php put ...
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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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421 views

Proxmox VE Logical Volume in RAW format?

I added a Volume group in Proxmox VE as Storage for KVM VMs. A new Logical Volume will be created for each VM, but in Proxmox VE under The Defined Storage which shows list of created Logical Volumes I ...
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1answer
463 views

high disk usage = io-bound on an apache + postgresql web server?

I have a server running apache, postgresql, and a lot of sites, and my graphs from my hosting provider indicate basically constant disk thrashing. 10k/s disk usage. This seems like a bad idea, but I'm ...
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420 views

I/O limits in FreeBSD

I am searching for a method to implement per Jail I/O limits in FreeBSD, as linux have from a long time now. During my research I stumbled upon: http://info.iet.unipi.it/~luigi/geom_sched/ My ...
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3answers
2k views

RAID10 without write-back cache = horrible write performance?

I have just provisioned a dedicated server on singlehop. I'm running it through some tests to know what to expect performance-wise. On the I/O side (with 4 1TB disks in RAID 10) I get: write-cache ...
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2answers
1k views

How iostat figures out to take CPU idle time to consider as %idle or %iowait?

I was going through iostat man page. According to it, %iowait Show the percentage of time that the CPU or CPUs were idle during which the system had an outstanding disk I/O request. %idle ...
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2answers
541 views

Testing a production hard hard / debugging high I/O Load

I've been getting a lot of high load lately on this server more so then it should for what little is on this system. Seems like just the simplest stuff using the disk like a YUM update will spike the ...
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3answers
222 views

How to arrange 2 SSD with 2 SATA? [closed]

I like to have best io performance as well as good capaciyy and reliability out of a server that hosts a busy forum, which involves loads of static files download. I am wondering what is the best plan ...
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0answers
44 views

How can I measure disk cache churn on Linux? [duplicate]

Possible Duplicate: Is there a way to get Cache Hit/Miss ratios for block devices in Linux? I have a file server which serves out large (25GB-1TB+) files over the network from local ...
0
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1answer
578 views

How to check which processes are deleting files without using inotify or auditd? [closed]

I'm trying to figure out which processes are deleting files from a specific directory on my CentOS server. I looked at inotify, but all this does is to tell me how many file deletions are occurring; ...
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2answers
406 views

How to figure out which processes are deleting files from a specific directory?

I'm trying to figure out which processes are deleting files from a specific directory, so I want to set up and run auditd on my system. I've set up the following rule in audit.rules: -w S unlink -S ...
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1answer
501 views

What buffer size should I use to maximize disk I/O bandwidth? (16Kb, 32Kb, 64Kb, etc.) [closed]

I am trying to write a file as fast as I can through a buffered FileChannel similar to a BufferedOutputStream. I am wondering what is the optimum chunk of data I should use per write call to maximize ...
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574 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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3answers
2k views

Linux utility to record IO statistics (random/sequential, block sizes, read/write ratio)

As part of provisioning our new server (see other SF) I'd like to find out the following: ratio of random to sequential reads & writes amount of data read & written at a time (pref in ...
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1answer
1k views

Debian: nginx using an extreme amount of disk I/O

We're currently haveing an issue with one of our nginx servers. It's using an extreme amount of disk I/O. It's the / (root - cciss/c0d0) partition that's being abused. See picture of iotop here: ...
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142 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
71 views

Partitioning disk I/O on linux

I have a server that runs two different workloads: heavy, linear write (stores all network traffic as pcaps); and a transactional DB workload where IDS alerts are written to (frequent inserts) and ...
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2answers
4k views

Very high load, apparently caused by pdflush

I have a server that's running CentOS 5, and it will periodically (a couple of times a day) have enormous spikes in load, and the whole server will grind to a halt. After a couple of minutes, the load ...
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3answers
331 views

Analysing Disk IO Traffic

I am running a web server (Ubuntu 11.04) that exhibits unexpected high write traffic. When the server is not supposed to write at all, the amount of write traffic is comparable to the read traffic. ...