1
vote
1answer
75 views

6 times slower disk write in RAID10 on Ubuntu 14.04 after rebuild

OS: Ubuntu 14.04 LTS Software Raid 10: 4x120Gb Intel 530 SSDs Initial tests: 1.2 GB/s Write 5.2 GB/s Read I did some tests to check if everything will go alright with a failed disk: I set as ...
0
votes
0answers
15 views

sar -b reports much too high statistics, are the I/O counted twice?

On a Linux server sar -b reports much too high read block statistics, sometimes 3.500.000 readb/s peak and around 2.500.000 readb/s sustain, which makes more that 1 gigabyte/s (according to the sar ...
2
votes
0answers
36 views

actual disk iops and write merging

/dev/sdb has LVM and exposes a single logical volume, dm-0. While writing to dm-0, /proc/diskstats reports: # of writes completed sdb 29646717 dm-0 131315099 # of writes merged: sdb 101668283 dm-0 ...
1
vote
0answers
16 views

SMI generation / detection in GRUB / real mode vs. in Linux

I'm trying to get an idea of the frequency and duration of SMI events on a Supermicro X10SAE C226 board (2.0a BIOS) with E3-1245v3 Haswell CPU. The Intel BIOS Implementation Test Suite (BITS) SMI ...
3
votes
2answers
235 views

Best practice on Linux servers and CPU/power throttling?

I am running a couple of Debian 6 (2.6.32) and 7 (3.2) Linux servers and all of them have energy saving settings enabled in their BIOS. Furthermore Linux shows that the CPUs are throttled if the ...
-2
votes
1answer
70 views

Streaming Server Network Performance [duplicate]

I have server Linux based on centos 6.5 final 64bit , ram 128 G.B dual E5-2650 processor Hard disk : 4 SSD Hard disk RAID-5 Network Speed 1/Gbps Bandwidth Speed 500/Mbps up to 3/Gbps My ...
0
votes
0answers
112 views

On a system with 64GB mem the Linux Buffer run full while copying with dd to dev null and io stops till manual drop_caches

I am running a server with linux software raid 10. It is a dual CPU system with 64GB Ram. 2x16GB dimms related to each of the CPUs. I want to use dd to backup kvm virtual machines and run into a ...
1
vote
0answers
43 views

IRQ not handled by all CPUs

I have a problem about balancing irq. I took irq numbers from /etc/interrupts and assigned each irq to each of 24 CPUs as this tutorial says for i in {143..166};do cat /proc/irq/${i}/smp_affinity; ...
4
votes
6answers
367 views

When is it time to add more cores to your virtual server? [closed]

I have a Linux (RHEL 5.8) server with Java 7 and Tomcat 7. The performance is poor, and I am pretty sure it's the DB queries that are slow. We have 2 cores right now, and load average never exceeds ...
3
votes
1answer
94 views

iozone: 5 concurrent threads random read of 300K blocks does more ops/s than using only one thread, what could be the underlying reason?

The partition is in RAID1 using software RAID. Command line used: iozone -s 190g -r 300k -O -b test_file OPS Mode. Output is in operations per second. ...
0
votes
3answers
114 views

Linux: Get information/stats about storage network

I want to know as much info as possible about the SAN a linux server is connected to. What commands will give me the most comprehensive view? Simply knowing the WWN of LUNS doesn't do much for me. ...
0
votes
0answers
48 views

when and how to appropriately use /proc/sys/vm/drop_caches

You can clear page cache with /proc/sys/vm/drop_caches. Can someone provide a practical explanation of how this works, when as a sysadmin you would want to do this, how to determine if your system ...
1
vote
1answer
177 views

MySQL high CPU usage on small website

I have a small website hosted on a dedicated server (FreeBSD 9.2, MySQL 5.6.1 and php 5.5.5). The problem is that MySQL eats a lot of cpu resources even if the website have a few visitors. The ...
0
votes
1answer
52 views

size of extent on LVM2

in LVM1 there was a limit of 65k extends. So size of extent had to been chosen carefully between wasted space on partitions (to big extent) and maximal possible size of logical volume (too small ...
0
votes
1answer
135 views

Abnormal CPU usage during Disk Write Operations

I have a decent CentOS 6.5 dedicated host (CentOS 6.5/E3-1230 3.2Ghz Quad Core + HT/16GB/Software Raid 1 SATA II/WD2503ABYX/ext4) with the default CentOS kernel and "elevator=deadline" in grub. I/O ...
0
votes
0answers
10 views

Scopserv System Load Average

Firstly, apologies for what will be a slightly less than technical explanation of the problem I am facing - I am not a SysAdmin and therefore have a somewhat limited understanding of the issue I'm ...
4
votes
2answers
652 views

VMXNET3 performance on Linux on ESX 5.0

What kind of performance can I expect from VMXNET3 adapter when running two Linux guests on the same VMware ESX private network defined between those guests? I use VMXNET3 adapter for communicating ...
0
votes
1answer
85 views

Improve Disk Performance of a Linux 2.4 Guest on KVM Host

I have a server running Linux 2.4, and I'd like to virtualize it using KVM. I can run it with a IDE controller, but my applications require more disk performance. The best existing solution is using ...
4
votes
2answers
215 views

Does LXC container performance depends of host load?

I am wondering if LXC could offer a full isolated benchmarking environment. Let's say we have 2 identical machines, with the same fresh Linux and without network connection. First machine has a load ...
1
vote
3answers
346 views

How many IOPS do I need? My workload bottleneck is storage

How can I know how many IOPS I need my storage to deliver for my overloaded Linux server? I have a server and I know it has storage as its bottleneck. I would like the bottleneck not to be storage, ...
1
vote
2answers
59 views

Splitting web project across multiple partitions on Linux (SSD, HDD and RAM Disk)

I've got a web project that pretty much consists of three parts: Code, Assets and Cache. I'm thinking of splitting it through multiple drives - Put my whole Code into SSD partition, Assets onto big ...
2
votes
1answer
50 views

Server load avg. hitting 16-20, but all resources under 90% usage?

As you can see in the image shared below, the server load peaked to almost 20 but the CPU, RAM, DISK IO and Network I/O remained well under their full capacity. My question is: 1). What caused the ...
0
votes
2answers
34 views

Apache Configuration not use server capabilities

I have a web server with 16 GB of RAM. The server has a good traffic and have pics of 300 simultaneous requests. Unfortunately when these peaks arrive queries fall into error or are very very slow. ...
2
votes
0answers
69 views

How to debug sluggish process performance

I have a test application which writes a string to a file 10000 times. I run this on two servers and I get totally different results. [SYSTEM 1] $ time ./test_depth real 0m0.152s user ...
1
vote
0answers
114 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 ...
-1
votes
1answer
39 views

Firewall Connections fail to open under load

Problem : During High load , our applications are encountering errors : java.net.connection Time out. After some investigation , we found out that it was Firewall the root cause, but still don't know ...
0
votes
3answers
205 views

Does software RAID-0 really improve performance?

I am going to lease a server and I have two options, SATA or SSD, I decided to save the money and go for the SATA option. But I do not need all that storage they are giving me! So I thought MAYBE I ...
2
votes
0answers
120 views

mdadm raid10 or nfs performance issues?

I have a fresh mdadm RAID10 device which is healthy, built from 4 x 7200rpm SATA 3 drives: # cat /proc/mdstat Personalities : [raid10] [raid1] md2 : active raid10 sdc3[5] sda3[4] sdb3[1] sdd3[3] ...
4
votes
1answer
212 views

iSCSI TGTD over InfiniBand Performance

I have just configured a server-to-server 4x SDR InfiniBand link to increase bandwidth for the backend storage of my virtual machines, specifically a database server. I am using iSCSI with TGTD on ...
1
vote
1answer
90 views

Choosing the right database/storage engine for iptables ulogd

I'm looking for some help choosing a database backend for a iptables ulogd setup. We are going to swap out our current proprietary firewall solution with iptables and one of the requirements is to ...
1
vote
1answer
281 views

3ware card in RAID-5 configuration slow and causes load when writing

I have a 1Gb/s bandwidth between my computers. The source can actually read and send data at 25MB/s via SSH. My test file is 4GB, I use scp without compression for the test transfer. The rate is ...
1
vote
0answers
127 views

Apache AB results: why does adding concurrency not increase requests processed per second?

So I've been trying to use apache ab to benchmark performance, but I'm having trouble understanding why I'm getting these results. FYI, its a PHP app using Zend Framework, mySQL database, and mostly ...
0
votes
0answers
103 views

Subversion performance issue on Linux

My developers is complaining our SVN is slow. This is the data they collected:http://i.stack.imgur.com/SmYUS.jpg. The SVN server is on Linux in Canada and developers using Cygwin on Windows in UK. So ...
3
votes
1answer
158 views

IO related performance bottleneck on a LAMP server

I am administering a big LAMP server with some thousand users. About a week ago, things slowed down, and the only thing I see that the IO latency is increased dramatically. Users experience slow page ...
5
votes
2answers
1k views

Relation between disk IOPS and sar tps

I'm trying to estimate IOPS requirements of my application running on 32-bit CentOS 6.2. I started to take some measurement on a machine with SATA disks and I'm quite confused of difference between ...
0
votes
0answers
184 views

Server & Mysql Config for Magento

I will appreciate if someone can help us as we think our server admin has no clue. We are having issues with our server such as mysql using too much CPU sometimes up to 70%. Especially when security ...
0
votes
1answer
103 views

Trading Engine running on RHEL 5.x [closed]

Before asking question quick background about myself working at one of trading company this is my 1st job as sysadmin I have finish my RHCE no experience how production server work. In our company ...
0
votes
3answers
333 views

Linux server became extremely slow

I have a file sharing website, and my files hosted in a server with those system specifications: 32GB RAM 12x3TB 2x Intel Quad Core E5620 I have files in this server up to 4gb for each file. 446gb ...
0
votes
0answers
97 views

How to find out which process is hogging the linux server?

We have a RHEL server. Today it suddenly became slow. Symptoms - It was responding slow to ping queries from other server. When I try to login using ssh, it was taking about 10 seconds to login. I was ...
1
vote
1answer
309 views

How to erase a SSD to restore factory performance in Linux?

Due to big performance issues with an mdraid-1 array I'd like to pull down from the array one of the devices (Samsung 840 Pro), erase it to restore factory performance and re-add it to the array. The ...
0
votes
0answers
224 views

Configuring ubuntu web server for wordpress stress test with apache jmeter

sorry for my english and the wall of text in advance. I've been given a project where I have to setup and configure a server with wordpress in a local environment, for stress/load testing purposes. ...
2
votes
1answer
3k views

Improving OpenVPN Performance

I've been trying to improve my OpenVPN performance and this is my current setup: cat /etc/openvpn/server.conf port 443 #- port proto tcp #- protocol dev tun #tun-mtu 1500 tun-mtu-extra 32 #mssfix ...
2
votes
1answer
565 views

How to achieve multiple NFS/TCP connections to the same server?

I'm trying to maximize the NFS/TCP bandwidth between a Linux client and a single NFS server over a 10Gbps link. Although each NFS mount has its own device (major/minor), everything comes down to a ...
1
vote
1answer
92 views

How does it harm if I install JDK on my ubuntu server when JRE is just enough for me?

I just need JRE for my programs. But how does it harm if I use JDK when JRE is enough for my webserver? Does it only mean more harddisk space for JDK & except for that, no other waste? I use ...
2
votes
1answer
78 views

Creating “Odd” Size Disks in VmWare/Linux

I believe I suffer from "everything must be in powers of 2" syndrome. When asked to create a 30G disk in VmWare for a VM I want to create a 32G disk. If someone needs 256G of storage using LVM I ...
0
votes
1answer
148 views

current my.cnf configuration

Hello serverfault community, I have a medium sized VPS on which I run 2 Magento installations, a few static pages as well as several WordPress / Joomla installation - all personal websites and ...
3
votes
2answers
217 views

Wifi performance is slow only when there are multiple radios in one router

I have a wireless network setup like this: Laptop \ | Wifi Router A | Wifi Router B | Wifi Router C | \ | / \ | / \ | / ...
0
votes
1answer
67 views

How can I prevent my server's background data processing tasks from slowing down the whole server?

Apologies for the inexpertly phrased question. I'm not quite sure how to put it. My Linux server: Serves web pages to users Does lots of data processing and gathering in the background I'd love ...
0
votes
1answer
52 views

What does negative value of -1 in kB_rd/ and kB_wr/s mean in PIDSTAT command

This is a sample output from running pidstat. minflt/s majflt/s VSZ RSS %MEM kB_rd/s kB_wr/s kB_ccwr/s 49 0 217532 18784 0.01 -1 -1 -1 Can you ...
3
votes
2answers
412 views

linux: how to simulate hard disk latency? I want to increase iowait value without using a cpu power

Is it possible to set an arbitrary delay for I/O operations? I would like to learn how do iowait and disk %util impact the performance. There are a lot of tools to stress the disk (bonnie++ etc.) but ...