0
votes
1answer
76 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 ...
0
votes
1answer
140 views

Finding root cause of 99.99% iowait with 0% SWAPON

Users and DBAs are complaining that "Oracle is slow" on our OEL servers. The only thing I have found from the OS standpoint is that there are some strange IOWAIT stats from iotop. Output from iotop: ...
1
vote
2answers
137 views

High Disk I/O on server reboot

A CentOS 5.8 machine has high Disk I/O upon starting up. The processes taking up disk IO are kmirrord, kjournald and pdflush. I have done the performed the following: 1) Mounted the filesystem with ...
4
votes
4answers
665 views

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) ...
6
votes
3answers
335 views

How to keep subtree removal (`rm -rf`) from starving other processes for Disk I/O?

We have a very large (multi-GB) Nginx cache directory for a busy site, which we occasionally need to clear all at once. I've solved this in the past by moving the cache folder to a new path, making a ...
0
votes
0answers
67 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 ...
0
votes
3answers
228 views

Dramatic disk I/O performance difference for two disks on same machine

A small machine (1 core, 1 GB RAM, CentOs 6.3) virtualized via Citrix Xen has 3 virtual disks with very different sizes. > cat /etc/fstab (snippet) ... /dev/mapper/vg_stagingnfs-lv_root / ext4 ...
4
votes
1answer
207 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 ...
5
votes
1answer
281 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 ...
2
votes
3answers
453 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 ...
3
votes
2answers
2k 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 ...
0
votes
1answer
260 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 ...
1
vote
3answers
1k 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 ...
1
vote
2answers
855 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 ...
3
votes
0answers
43 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 ...
2
votes
1answer
897 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: ...
6
votes
1answer
121 views

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 ...
4
votes
2answers
664 views

Why does a CP command on linux consume CPU?

I just run a copy command for two large directories with a small number of huge files and I see my cp process is consuming around half a core in top: 51116 root 20 0 110m 876 688 D 43.9 ...
0
votes
2answers
150 views

Possible disk IO problem. Help to be sure.

Since some time days ago, one of my servers started crashing. Currently it is crashing almost every day. Sometimes, over once a day. Only a restart can solve. The last time the problem happend, the ...
1
vote
1answer
490 views

IO and bus errors on Ubuntu Server

I've got an old computer running Ubuntu Server 10.04, which acts as router, file server and web server. A couple of weeks ago I inserted a PCIe video card, since the motherboard did not have any video ...
1
vote
1answer
461 views

Ramdisk vs Build-In IO Caching on Windows

I'm trying to understand the built-in IO cache on Windows. If an application writes to a file, and then reads/writes it multiple subsequent times, it seems that the IO cache should allow this to ...
0
votes
4answers
572 views

How can I get a list of Programs doing Disk IO?

I have a server (running CentOS 5) and I need to figure out which programs (MySQL, Apache, etc) are doing the most Disk I/O? Is there a command that will allow me to calculate an average over time?
2
votes
2answers
289 views

comparing disk performance of machines

I am in the process of moving applications running on old Linux machines onto VMs. As part of this, I need to justify the VMs have at least the capacity (i.e. CPU speed, RAM, disk, disk speed, network ...
3
votes
1answer
553 views

Measuring Disk IO programmatically

I want to measure some numbers related to disk io in a given timespan, programmatically. This means I don't want to spawn a process like iostat to get my numbers, by prefer to read something from proc ...
1
vote
2answers
876 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 ...
2
votes
2answers
314 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 ...
3
votes
7answers
4k 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
226 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, ...
1
vote
2answers
908 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 ...
2
votes
1answer
311 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 ...