Download of the day: Vmware 2.0 Virtualization Solutions Beta Software

Posted on in Categories CentOS, Download of the day, Hardware, High performance computing, Linux, Linux Virtualization, Networking, vmware last updated October 29, 2008

VMware Server is an entry-level server virtualization solution, which is proprietary, freeware software. VMware released version 2.0 beta of Server on July 1, 2008. New version provides appliance like control using nothing but a webbrowser.

Load Balancer Open Source Software

Posted on in Categories Hardware, High performance computing, Linux, Linux Scalability, Linux Virtualization, Monitoring, Networking, RedHat/Fedora Linux, Storage last updated March 11, 2008

I’ve worked with a various load balancing systems (LBS). They are complex pieces of hardware and software. In this post I will highlight some of the open source load balancing software. But what is load balancing?
It is nothing but a technique used to share (spared) load / services between two or more servers. For example, busy e-commerce or bank website uses load balancer to increase reliability, throughput, uptime, response time and better resource utilization. You can use following softwares as an advanced load balancing solution for web, cache, dns, mail, ftp, auth servers, VoIP services etc.

Linux Virtual Server (LVS)

LVS is ultimate open source Linux load sharing and balancing software. You can easily build a high-performance and highly available server for Linux using this software. From the project page:

Virtual server is a highly scalable and highly available server built on a cluster of real servers. The architecture of server cluster is fully transparent to end users, and the users interact with the cluster system as if it were only a single high-performance virtual server.

=> Project Web Site

Red Hat Cluster Suite

It is a high availability cluster software implementation from Linux leader Red Hat. It provide two type services:

  1. Application / Service Failover – Create n-node server clusters for failover of key applications and services
  2. IP Load Balancing – Load balance incoming IP network requests across a farm of servers

=> Product web page

The High Availability Linux Project

Linux-HA provides sophisticated high-availability (failover) capabilities on a wide range of platforms, supporting several tens of thousands of mission critical sites.

=> Project web site

Ultra Monkey

Ultra Monkey is a project to create load balanced and highly available network services. For example a cluster of web servers that appear as a single web server to end-users. The service may be for end-users across the world connected via the internet, or for enterprise users connected via an intranet.

Ultra Monkey makes use of the Linux operating system to provide a flexible solution that can be tailored to a wide range of needs. From small clusters of only two nodes to large systems serving thousands of connections per second.

=> Project web site

Personally, I’ve worked with both LVS and Red Hat Cluster Suite and I highly recommend these softwares.

How do I find out Linux Resource utilization to detect system bottlenecks?

Posted on in Categories Linux, Troubleshooting last updated November 23, 2007

Q. How can I find out Linux Resource utilization using vmstat command? How do I get information about high disk I/O and memory usage?

A. vmstat command reports information about processes, memory, paging, block IO, traps, and cpu activity. However, a real advantage of vmstat command output – is to the point and (concise) easy to read/understand. The output of vmstat command use to help identify system bottlenecks. Please note that Linux vmstat does not count itself as a running process.

Here is an output of vmstat command from my enterprise grade system:
$ vmstat -S M

procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
3  0      0   1963    607   2359    0    0     0     0    0     1 32  0 68  0


  • The fist line is nothing but six different categories. The second line gives more information about each category. This second line gives all data you need.
  • -S M: vmstat lets you choose units (k, K, m, M) default is K (1024 bytes) in the default mode. I am using M since this system has over 4 GB memory. Without -M option it will use K as unit

$ vmstat

procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
3  0      0 2485120 621952 2415368  0    0     0     0    0     1 32  0 68  0

Field Description For Vm Mode

(a) procs is the process-related fields are:

  • r: The number of processes waiting for run time.
  • b: The number of processes in uninterruptible sleep.

(b) memory is the memory-related fields are:

  • swpd: the amount of virtual memory used.
  • free: the amount of idle memory.
  • buff: the amount of memory used as buffers.
  • cache: the amount of memory used as cache.

(c) swap is swap-related fields are:

  • si: Amount of memory swapped in from disk (/s).
  • so: Amount of memory swapped to disk (/s).

(d) io is the I/O-related fields are:

  • bi: Blocks received from a block device (blocks/s).
  • bo: Blocks sent to a block device (blocks/s).

(e) system is the system-related fields are:

  • in: The number of interrupts per second, including the clock.
  • cs: The number of context switches per second.

(f) cpu is the CPU-related fields are:

These are percentages of total CPU time.

  • us: Time spent running non-kernel code. (user time, including nice time)
  • sy: Time spent running kernel code. (system time)
  • id: Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time.
  • wa: Time spent waiting for IO. Prior to Linux 2.5.41, shown as zero.

As you see the first output produced gives averages data since the last reboot. Additional reports give information on a sampling period of length delay. You need to sample data using delays i.e. collect data by setting intervals. For example collect data every 2 seconds (or collect data every 2 second 5 times only):
$ vmstat -S M 2
$ vmstat -S M 2 5

procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
3  0      0   1756    607   2359    0    0     0     0    0     1 32  0 68  0
3  0      0   1756    607   2359    0    0     0     0 1018    65 38  0 62  0
3  0      0   1756    607   2359    0    0     0     0 1011    64 37  0 63  0
3  0      0   1756    607   2359    0    0     0    20 1018    72 37  0 63  0
3  0      0   1756    607   2359    0    0     0     0 1012    64 37  0 62  0
3  0      0   1756    607   2359    0    0     0     0 1011    65 38  0 63  0
3  0      0   1995    607   2359    0    0     0     0 1012    62 35  2 63  0
3  0      0   1731    607   2359    0    0     0     0 1012    64 34  3 62  0
3  0      0   1731    607   2359    0    0     0     0 1013    72 38  0 62  0
3  0      0   1731    607   2359    0    0     0     0 1013    63 37  0 63  0

This is what most system administrators do to identify system bottlenecks. I hope all of you find vmstat data is concise and easy to read.

See also: