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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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Why is io scheduler not merging requests?

After some time (or amount of data written) after server reboot the write speed drops to less than 1 MB/s. This is regardless of which filesystem (also raw partition) and regardless of HDD (HW RAID) or SSD (SW RAID with SSD connected to motherboard…
Marki555
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I/O high on DRBD disk drbd10 on stacked site

We have 4 Redhat Boxes Dell PowerEdge R630 (say a,b,c,d) having the following OS/packages. RedHat EL 6.5 MySql Enterprise 5.6 DRBD 8.4 Corosync 1.4.7 We have setup 4-way stacked drbd resources as below: Cluster Cluster-1: servers a and b connected…
Manu
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Filesystem Performance for LUKS Encrypted Volumes?

As you can format a LUKS volume with any filesystem you want, are certain filesystems better-suited to IO performance against an encrypted filesystem? Specifically, I'm wondering about a loop device with a file sitting on an ext4 partition. As all…
Will
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KVM bad IO sync performance in Linux guest

I'm setting up virtualized Ubuntu 15.10 guest inside Ubuntu 15.04 server using libvirt and KVM. Storage in host system: # mount | grep ext4 /dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro,data=ordered) /dev/sdb1 on /media/hdd type ext4…
dsi
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99% disk IO spikes with Percona

So we have a server that has seemingly random spikes in disk I/O, going up to 99.x% at random times and for no obvious reason, staying high for a while, and then going back down. This didn't use to be an issue, but recently the disk I/O has been…
user284587
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4 answers

Changing the I/O scheduler for a specific disk

I would like to change permanently the I/O scheduler for a specific disk on Fedora 20. According to what I have found, this can be achieved by executing the following shell line as root: echo {SCHEDULER-NAME} >…
Laurent
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Linux page cache slows down IO on dual cpu server with 64GB ram

I have a massive problem with the linux page cache which slows down the IO. For instance if I copy a lvm partition with dd, linux cache the data in the buffers or caches (free –m). That is not the problem, but after the buffer reaches a special…
user219392
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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 from disk per second. Note:…
simonp
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How to calculate the required EBS PIOPS for our mongo server?

We want to use provisioned IOPS EBS volume on our mongo machines, I'm a bit confused on how to calculate the number of provisioned IOPS to use. Currently we're getting an average of 25 IOPS (read + write) per volume (we use 4 EBS volumes combined),…
Nimrod Gutman
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How to monitor NFS load from userland?

Apologies if I'm not using the proper jargon (although I'm a longtime linux user, I'm not an admin) or if this is a FAQ (though searching SE got lots of hits, I didn't see anything quite like this question): I'm a user on a science cluster (with…
TomRoche
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Disk performance below expectations

this is a follow-up to a previous question that I asked (Two servers with inconsistent disk speed). I have a PowerEdge R510 server with a PERC H700 integrated RAID controller (call this Server B) that was built using eight disks with 3Gb/s bandwidth…
paulH
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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 option, bad superblock on /dev/hda2 dmesg is…
BerserkEVA
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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 seemingly unrelated to MySQL usage. The machine is only…
mloc123
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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 if=/dev/zero of=test1 bs=1048576 count=2048 echo…
yby
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How can I measure disk cache churn on Linux?

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 storage. I'm trying to decide whether adding more RAM for the…
regularfry
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