LKJ.net

Memcached replication for data redundancy

Tech Guy — Sun, 11 Dec 2011 14:58:48 +0000

A lot of high performance web sites use memcached to speed up caching and serve content much faster to the web visitors. By default memcached doesn’t offer any data redundancy and no replication feature – memcached uses server RAM to store all data and if the server hardware fails or it is rebooted all data that’s stored in the memcached daemon will be lost. In order to increase memcached data redundancy and offer high availability you should check out RepCached (Web site: http://repcached.lab.klab.org/ ) – it offers multi-master and asynchronous replication for 1.2.x memcached versions.

You can use Layer-4… Read the rest of this entry »

Vmware Vsphere error – A specified parameter was not correct spec.sharesinfo.shares

Tech Guy — Sat, 10 Dec 2011 17:31:21 +0000

I tried to edit resource allocation settings and got the following error using Vmware Infrastructure client:

A specified parameter was not correct spec.sharesinfo.shares

To fix the problem and edit resource allocation you should edit values directly from the virtual machine
settings.

Login in as Administrator into Vmware Virtual Center using Vmware Infrastructure client. Select the virtual machine you want to modify. Edit Settings. Click Resources tab. Modify the required resource values as required.

G-WAN super performance web server daemon

Tech Guy — Sun, 13 Nov 2011 07:54:56 +0000

At LKJ.NET blog we usually cover new technologies that allow to scale your web site to new heights. A few weeks ago I spot a new and promising star in the universe – G-WAN web server daemon/software. From the benchmarks it claims to be the fastest web server daemon available on the planet easily beating Nginx and Lighhtpd with a large margin (3-4 times usually). It can easily saturate 10G network up link by serving static content and is ideal for Web 2.0 noSQL stores and similar technologies where phenomenal high speed and low latency is a must.… Read the rest of this entry »

curl-loader installation from source on Centos 5.6

Tech Guy — Mon, 05 Sep 2011 16:29:17 +0000

For those who are having problems installing curl-loader under Centos platforms please read this guide.

This guide applies to Centos 5.5 and 5.6 versions, 64-bit platforms.

Install the following packages:

yum install libevent libevent-devel

Download curl-loader from: http://sourceforge.net/projects/curl-loader/

replace in Makefile
OPENSSLDIR=$(shell $(CURDIR)/openssldir.sh)
to
OPENSSLDIR=/usr/lib64/openssl

Run with root user:

./configure
make
make install

If you are getting the following error:

curl-loader: error while loading shared libraries: libcares.so.2: cannot open shared object file: No such file or directory

you are missing c-ares package..you can try to install from Centos yum repository:

yum install c-ares

… Read the rest of this entry »

Been a bit busy, sorry

Tech Guy — Wed, 31 Aug 2011 19:36:00 +0000

Sorry guys, I’ve been a bit busy lately working on Vmware migrations and doing a horizontally scalable web platform. I will have new technical posts published shortly that will include Linux Virtual Server (LVS) configs and UCARP fail-over as well as load balancing and SSL acceleration using Nginx.

Increasing httperf maximum number of open descriptors from 1024 to 65535

Tech Guy — Thu, 07 Jul 2011 20:17:38 +0000

By default httperf on Linux compiles with 1024 open descriptors and that can be a problem when you plan to test high bandwidth and many concurrent connection web servers.

For safety you can edit /etc/security/limits.conf however you will also need to change the following file before you compile httperf software:

/usr/include/bits/typesizes.h

and find the following line:

/* Number of descriptors that can fit in an `fd_set’. */
#define __FD_SETSIZE 1024

and replace it to

#define __FD_SETSIZE 65535

Now you can compile httperf.
The original string that’s displayed when you run httperf without editing typesizes.h definition file:

httperf: maximum

… Read the rest of this entry »

Playing around with Linux Virtual Server (LVS)

Tech Guy — Wed, 29 Jun 2011 19:16:45 +0000

I haven’t disappeared folks – I’ve been playing around with Linux Virtual Server (LVS) in the last days and it’s been actually a great experience. Please expect LVS Layer 4 load balancing posts very shortly.

I am currently using Centos 5.6 version with built in IPVS module, but will be compiling custom kernel for best performance. Please hold on – I will have new posts shortly.

Hard disk defragmentation on Windows XP and later

Tech Guy — Sun, 12 Jun 2011 12:50:16 +0000

To speed up your desktop or laptop hard drive performance it’s recommended once in a while to perform a hard disk defragmentation. Of course you can install expensive SSD drive and forget about the “slow” SATA drives, however disk defragmentation offers free performance boost for existing hard drives.

You can run hard drive defragmentation from a command line or graphical interface.

For Windows XP in graphical mode run:

Start -> All programs -> Accessories -> System tools -> Disk defragmenter

Select the disk and click Analyze option. The disk blocks, files and directories will be evaluated and the program… Read the rest of this entry »

Windows XP recovery virus removal

Tech Guy — Tue, 07 Jun 2011 19:25:03 +0000

My friend’s PC got infected with Windows XP Recovery virus and he asked my help to get rid of it. This virus is quite annoying – it hides all files, cleans desktop and program menu and offers you to buy software that will repair your PC. What a joke.

The following popup appeared:

I tried downloading PC Tools, that did detect this malware, but asked me to register and buy a full version to remove this virus. No, I didn’t want to buy anything and started some searching again. After a few searches I found Malwarebytes Anti-Malware software that… Read the rest of this entry »

Increase vBulletin and WordPress MySQL speed by using fast SSD drives

Tech Guy — Sun, 29 May 2011 11:43:08 +0000

I’ve been consulting owners of very large blogs for a few years now and the last client was a very popular tech blog owner who’s web site has over 3.000.000 monthly visitors.

The server hardware specification:
8GB RAM
4 CPU Intel E5640 (16 cores in total)
1TB SATA HDD

This WordPress powered blog runs on LAMP platform with Nginx (my favorite!) front-end server, Apache and MySQL on one physical server. The problem was IO load – the IO time wait as reported by “iostat” utility was sometimes over 26%. The average server load was over 8 all… Read the rest of this entry »