0
votes
1answer
50 views

Strange CPU spikes with MySQL

On my server (ubuntu 12.04) mysqld started to show some strange CPU spikes. I've logged some of it as a sample: http://pastebin.com/4MwKUVwL The value after the triple dash '---' is the cpu usage ...
0
votes
1answer
40 views

RAID6 generates quite a IO wait at relatively low TPS

I have a RAID6 array made of 9 SATA3 disks @7200 RPM, 4TB in size. I have them partitioned with Gparted Live as GPT partitions, starting at the first megabyte. I am concerned about the read speed. ...
5
votes
1answer
125 views

Why iperf still reports 1Gbps performance when using bonding over two 1Gbps adapters?

As I understand it, bonding brings among other benefits the ability to increase the network speed between two machines in a LAN. Bonding [...] means combining several network interfaces (NICs) to ...
0
votes
0answers
20 views

does the number of lvm logical volumes affect ssd performance

Please let me know what your thought are on this. I've installed Ubuntu multiple times on a msata ssd mS200S3 120GB. There is a noticeable decrease of read performance on the exact same hardware for ...
1
vote
1answer
236 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 ...
3
votes
1answer
186 views

Upstart: Why two processes when running as a different user?

I want to keep a nodejs app running, so I followed this: http://howtonode.org/deploying-node-upstart-monit and installed Monit and Upstart which have been working perfectly for a couple of months. I ...
0
votes
1answer
75 views

S/W RAID6 and 4k sector format — slow resync

I'm looking for reason why Linux software RAID-6 re-sync is much slower than I expected. I have used 6 WDC WD40EFRX HDDs (with 4k physical sectors) to create RAID-6 array. $ sudo mdadm -v -C ...
0
votes
0answers
324 views

Optimizing disk performance on KVM VM configuration

I have a KVM host server running Ubuntu 12.04 LTS, bare bones installation with only KVM installed. The server has an 8 Core Intel(R) Xeon(R) CPU E3-1230 V2 @ 3.30GHz CPU with 32GB of RAM and SATA ...
0
votes
0answers
102 views

Ubuntu server router - only 50% of upload bandwidth

I've changed my internet connection to 400 mbps download and 400 mbps upload. Real speeds when computer connected directly to optical modem: 421/412 mbps for download/upload. My network structure is: ...
0
votes
0answers
50 views

RAID6 Ubuntu rebuild - how to calculate best parameters for fastest rebuild

I am doing a resync on a RAID6 array and I am looking at some 2 days to complete. I looked here for hints on how to speed it up, but I have, instead, managed to slow it down! HW details are: 10x 4TB ...
0
votes
2answers
120 views

Graceful way to rsync millions of files between two local folders

I want to rsync a folder with millions of files from a local directory to another, on a daily basis. The files themselves change very rarely. I want to reduce the impact on the running server, e.g. ...
2
votes
1answer
146 views

My Ubuntu VPS is not using available swap, even if OOM. What to do?

I recently added 1 GB of swap to my Ubuntu virtual private server to prevent MySQL crashes on RAM overloading. I followed this tutorial. I use htop to monitor resources. When I use loadimpact to test ...
0
votes
2answers
120 views

How to tell which script is slowing down the server the most?

As it happens often to coders, I had to take over someone else's code for this company, the server runs on Amazon Cloud (i2.xlarge) running ubuntu-saucy-13.10-amd64-server. (the guy left) The ...
1
vote
0answers
171 views

Reason for high CPU time when executing fio

After weeks of troubleshooting some performance issues I have on my VPS running Ubuntu 12.04 LTS, I am getting closer to the conclusion that the problem is related to IO. When I have a considerable ...
2
votes
3answers
509 views

How to troubleshoot performance issues of PHP, MySQL and generic I/O

I have a WordPress based website running on a shared hosting. Its response time is very decent (around 2s to retrieve the HTML page and 5s to load all the resources). I was planning to move it to a ...
1
vote
1answer
156 views

Why does my program run 2-4 times slower on a VPS?

I have a program (Node.js web application on Ubuntu) that loads in about 7 seconds on my home computer. Recently I copied it to a VPS, and there, it loads in 15-30 seconds. I am trying to find out ...
0
votes
1answer
34 views

Is it bad to have two webapps each on different servlet container than both on same, on a production server?

I need to run two webapps on a ubuntu VPS but one(my own webapp) prefers to run in Tomcat & other(Solr webservice) is preferable in Jetty. But I think running a separate server for each webapp ...
1
vote
1answer
95 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 ...
0
votes
1answer
165 views

How filter top output by the COMMAND column?

I want get the same result when pressing u to filter by USER, but instead using the column COMMAND and of course, I need this live (I mean, updating constantly) ;) I'm on Ubuntu.
2
votes
1answer
421 views

Should CPU usage be so low while memory usage is high on heavy mysql server?

I'm using ubuntu server 12.04 x64. The server receives a lot of requests to mysql through apache web server (it's light interface). From mysql stats I see there is approx 250 queries / second from 8 ...
-2
votes
2answers
73 views

How should I host a website with infrequent, planned load spikes? [closed]

I have a smallish site which I expect to have extremely high concurrent traffic for a few hours each month. I'm trying to work out what hosting solution will ensure the site never goes down. Here are ...
1
vote
0answers
85 views

File I/O Throughput

I have an IBM x3650 M4 server (64-bit) running Ubuntu 13.04 Desktop (32-bit). I realize that this is a non-standard setup by it's being driven by other requirements. I am seeing slow file writes ...
3
votes
3answers
603 views

Is slow IO on my cloud server causing my slow server restart issues?

I'm running two servers on Rackspace cloud one for the web app and one for the db and redis instances. The web server has 1Gb of ram and single core. Nginx sits in front of unicorn which is running 2 ...
0
votes
0answers
68 views

Why parsing directories are so slow?

I have a directory with 136 000 files for a total of 1.8GB. The server has: 8 Cores - Intel(R) Xeon(R) CPU E5606 @ 2.13GHz 25GB RAM Ubuntu 12.04.2 LTS Hardware RAID 1 (LSI Logic / Symbios Logic ...
14
votes
4answers
1k views

How do limit disc i/o during backup?

I have a cron that basically do a simple "tar zcf" in the night. The server has: 8 Cores - Intel(R) Xeon(R) CPU E5606 @ 2.13GHz 25GB RAM Ubuntu 12.04.2 LTS Hardware RAID 1 (LSI Logic / Symbios ...
1
vote
4answers
130 views

Web server response time variability

I have Apache2 Web server and tiny PHP script <?php echo '1' When refreshing page the waiting time value in Google Developers Tools can vary from 24-26 ms to 300-350 or somtimes it is even more ...
2
votes
1answer
197 views

MongoDB CPU usage in top is confusing

I have an Ubuntu 12.04 VM running in VirtualBox that has a whole MongoDB cluster on it (4 data nodes, one config node, and a mongos router). When I look at "top", I see that each of those processes ...
0
votes
1answer
1k views

How to understand random 500 internal errors in Nginx?

Our server is showing a lot of 500 internal error pages for random requests. We know the app is working because our code is unit tested. The server setup is Nginx with Unicorn running a single Rails ...
3
votes
1answer
2k views

Whats the cause of VMWare esxi Ubuntu very slow disk performance (3MB/s)?

Currently I am running Zentyal Server(Ubuntu) as Guest on a esxi 5 host on a Adaptec raid controller RAID 10 with Enterprise WD hard drives, 8 Core CPU and 8 Gb of ram (I know a bit overkill) to ...
0
votes
1answer
179 views

Very slow ubuntu 12.04 server. Seems to have plenty of resources

I am experiencing slow page loads and slow SSH responsiveness, but when I run htop I appear to have plenty (1gb+) of available memory and the CPU seems to be pretty chilled. Is there a better way to ...
0
votes
1answer
285 views

What diagnostic tools for diagnosing problems on Ubuntu? [closed]

I recently had an ubuntu server slow to its knees, and when trying to figure out why I realized it didn't have iostat installed. The system was stressed out to the point where I couldn't install the ...
9
votes
5answers
678 views

How do I find the cause for a huge difference in performance between two identical Ubuntu servers?

I am running two Dell R410 servers in the same rack of a data center (behind a load balancer). Both have the same hardware configuration, run Ubuntu 10.4, have the same packages installed and run the ...
1
vote
1answer
655 views

Locate cause of high load. Checked CPU, Memory/Swap and IO - all low. Running Nginx, MySQL and PHP-FPM on this Ubuntu 12.04 box [duplicate]

Possible Duplicate: 100% CPU when doing 4 or more concurrent requests with Magento people. This is my first question, but this community has been helpful to me hundreds of times, so thank ...
0
votes
3answers
4k views

Why is UDP slower than TCP on Ubuntu Server?

I transfer data between two Ubuntu Servers (12.04) via iperf on 1Gb LAN. iperf -s <-> iperf -c <addr> -n2G TCP speed = 925 Mbits/sec iperf -su <-> iperf ...
1
vote
1answer
253 views

Ubuntu 10.04 - high load , low cpu, IO, and no swapping

Ubuntu 10.04 64bit - Kernel 2.6.36 Running as a Xen 3.4 guest. 8GB memory , no swap being used, no IO wait time, and 0% cpu. Yet high load. Why is this: 15:11:24 up 5 days, 3:22, 2 users, load ...
12
votes
4answers
4k views

Ubuntu's garbage collection cron job for PHP sessions takes 25 minutes to run, why?

Ubuntu has a cron job set up which looks for and deletes old PHP sessions: # Look for and purge old sessions every 30 minutes 09,39 * * * * root [ -x /usr/lib/php5/maxlifetime ] \ ...
2
votes
3answers
275 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. ...
0
votes
2answers
462 views

Server performance troubles - Finding the culprit

I have a small website with a streaming-chat. We really have not much traffic and a dedicated server. But now something bugs me. Sometimes the Server takes up to 20 seconds to respond to a request. ...
0
votes
3answers
94 views

Why aren't local requests almost instant?

This is purely out of curiosity, but with every local server I've ever setup, there has always been a 0.5-2 second delay until pages are displayed. Just as an example, I've setup a completely blank ...
2
votes
2answers
152 views

Is DNS caching common in production Ubuntu server

In Ubuntu, DNS is not cached. So if my program use a lot of DNS queries and it will be plainful. I knew in RHEL, they have nscd installed by default, so in Ubuntu, if I want to use the server as a ...
0
votes
0answers
378 views

Slow data transfer from shared folder on Ubuntu 11 Server

I have a Virtual Machine running on VirtualBox, on which I installed Ubuntu 11 Server (I left it "plain vanilla", it just runs Apache and MySQL). I created a shared folder with Samba and I can access ...
0
votes
1answer
517 views

Short write and read speed disk benchmarking

We're using cloud hosting for some of our backend servers and we noticed that performance on the disks (which as confirmed by the provider are shared with other customers) vary depending on the ...
0
votes
1answer
276 views

Slow performance by PHP directory operations on virtual machine (Ubuntu libvirt)

Some days ago I installed an Ubuntu server and two running virtual machines with libvirt. Everything works fine except one performance problem. Everytime when I call a PHP script with directory ...
1
vote
1answer
375 views

Slow performance over network (Ubuntu)

i did setup this NodeJs TCP Server and tested it with a message flooder. Just to see how the performance of the server is. While the message throughput is great if i run the server and the message ...
1
vote
1answer
307 views

Block illegitimate traffic (hackers, scrapers, spammers) to your website

According to a recent report from ZDNet, 31% of traffic is illegitimate (hackers, scrapers, spammers). The challenge as a sysadmin is to find a way to block that traffic without blocking your real ...
5
votes
1answer
656 views

Speed of different Linux distros - why the difference?

I have a piece of multi-threaded software which runs at different speeds under the latest ubuntu server, redhat enterprise and CentOS - all installed on the exact same server for comparison. Ubuntu ...
3
votes
2answers
785 views

What could cause very slow (3 MB/s) disk access on a Ubuntu guest running under Hyper-V?

I have a Ubuntu 11.10 x64 guest running under Hyper-V on Windows Server 2008 R2 SP1, configured according to these directions, including installation of the hyper-v modules. Network speed is fine (500 ...
10
votes
8answers
8k views

Should I completely turn off swap for linux webserver?

Recently my friend told me that it is a good idea to turn off swap on linux webservers with enough memory. My server has 12 GB and currently uses 4GB (not counting cache and buffers) under peak load. ...
0
votes
1answer
134 views

loading testing from a one ec2 linux/ubuntu instance to another ec2 linux/ubuntu instance

I wanna run a load/stress testing on ubuntu ec2 small instance. I could have done it using Jmeter from my laptop itself, but that would actually consume lot of bandwidth and also I feel I cant get the ...
0
votes
1answer
168 views

Is uploading a 500mb file to s3 an expensive operation? Any way to limit cpu usage etc?

On a production server, I'm planning on uploading a single file or a set of files that may be 500 megs in size. I havent' test it just yet, but just want some opinions on whether you think this will ...