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Questions tagged [io]

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

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

401 questions
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2 answers

How to set i/o priority for nfs client processes?

The configuration is: A linux server and a nas box (netgear) acting as nfs server. It is easy for a single process on the linux server to use all i/o bandwidth by simply copying a file from the nfs share to the nfs share. The i/o channel is jammed…
Moritz Both
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4 answers

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 relatively high (compare to the rest of the servers).…
grs
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6
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1 answer

RAID6 resync with fast writes but slow reads

I'm using Debian Jessie. # uname -a Linux host 4.9.0-0.bpo.3-amd64 #1 SMP Debian 4.9.30-2+deb9u5~bpo8+1 (2017-09-28) x86_64 GNU/Linux And have setup a RAID6. # cat /proc/mdstat Personalities : [raid6] [raid5] [raid4] [raid1] md0 : active raid6…
rabudde
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6
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1 answer

Centos7 - Buffer I/O error on dev sda, logical block xxxxxxxxx, lost async page write

I have a webserver that have the content in HP MSA2040 Storage (10 tb total storage). I keep getting error like below Jul 31 19:06:24 xxxxxxxx*** kernel: blk_update_request: I/O error, dev sda, sector 7094923416 Jul 31 19:06:24 xxxxxxxx*** kernel:…
Lunatic Fnatic
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6
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3 answers

Massive performance degradation on sustained sequential write

I'm in the process of migrating data into LUKS partitions. Now that the operating system drive is running off LUKS, I tried to start migrating the data drives. Then the server stopped responding. This LUKS device was opened: cryptsetup luksOpen…
Deltik
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6
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3 answers

Evaluating the CPU I/O wait on Linux

Doing a top to check the io wait, I get these figures: Cpu(s): 6.7%us, 1.4%sy, 1.2%ni, 85.5%id, 5.0%wa, 0.0%hi, 0.3%si, 0.0%st Looking at these figures (%us ~= %wa), do they mean that: there are almost as many CPU processes waiting than…
Toto
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6
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1 answer

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 that runs ubuntu 12.04 and hosts my postgresql 9.2…
Niels Kristian
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6
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1 answer

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 to further debug it, I'm asking for your ideas…
aef
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6
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1 answer

How to prevent IO Load under Linux for Video serving?

I'm currently serving videos of conferences via Nginx on 3 servers; 4 cores, enough memory (no swap used) and RAID-10 with 8 drives per server. Unfortunately iostat -xd 1 gives me 100% on all 3 servers and iotop shows Nginx eating that 99-100%.…
CharlesS
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6
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1 answer

Maximizing throughput of virtual file systems

I've been using a QEMU system to build software. The problem I've been having is that the system seems to suffer from extremely slow disk access. This is not necessarily a problem as it's not really a time-intensive operation, but I'd like to have…
amphetamachine
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6
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7 answers

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? Thanks.
Justin
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6
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4 answers

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, this is assuming the files will be accessed often --…
locke92
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6 answers

Find the bottleneck: disk I/O on Windows XP

One of our development boxes has developed a problem wherein performance will occasionally drop through the floor. When this happens, you can hear the hard drive thrashing, but I don't know what's causing it. This happens during periods of high…
Ben Blank
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5
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1 answer

Misunderstanding about Page Cache and dirty_background_bytes

I've been looking at this for a while now and things aren't lining up with my expectations, but I don't know if it's because something is off, or if my expectations are wrong. So, I've got a system with over 100GB of RAM, and I've set my…
psycotica0
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2 answers

Tuning sequential disk reads for performance

I am reading a large file sequentially from the disk and trying to understand the iostat output while the reading is taking place. Size of the file : 10 GB Read Buffer : 4 KB Read ahead (/sys/block/sda/queue/read_ahead_kb) : 128 KB The iostat…
Stormshadow
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