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cluster file system

Recently, I received a call from client about FTP server not working. Basically, someone was trying to
access networked file system mounts such as cifs and nfs via ftp. This is bad idea and it will result into problems because it is not supported by many applications (I'm not talking about cluster file system here). There are many issues with this kind of weird setup:

+ Permission problem
+ I/O Problem
+ Performance issue etc

Some FTP server do offer work around but I don't recommend exporting networked file system via another file system.

Bottom line, don't mix networked file system with each other.

Linux file systems have a number of limitations that make them a poor choice for large and high-performance computing environments. This article explains some of the pros and cons of Linux and old UNIX file systems:

I am frequently asked by potential customers with high I/O requirements if they can use Linux instead of AIX or Solaris.

No one ever asks me about high-performance I/O -- high IOPS (define) or high streaming I/O -- on Windows or NTFS because it isn't possible. Windows and the NTFS file system, which hasn't changed much since it was released almost 10 years ago, can't scale given its current structure. The NTFS file system layout, allocation methodology and structure do not allow it to efficiently support multi-terabyte file systems, much less file systems in the petabyte range, and that's no surprise since it's not Microsoft's target market.

=> Linux File Systems: You Get What You Pay For

What do you think?

This article explains howto setup and running with the Linux Virtual Server and Linux-HA.org's Heartbeat in 5 easy steps. You can construct a highly available Apache Web server cluster that spans multiple physical or virtual Linux servers with Linux Virtual Server (LVS) and Heartbeat v2:

Spreading a workload across multiple processors, coupled with various software recovery techniques, provides a highly available environment and enhances overall RAS (Reliability, Availability, and Serviceability) of the environment. Benefits include faster recovery from unplanned outages, as well as minimal effects of planned outages on the end user.

This article illustrates the robust Apache Web server stack with 6 Apache server nodes (though 3 nodes is sufficient for following the steps outlined here) as well as 3 Linux Virtual Server (LVS) directors. We used 6 Apache server nodes to drive higher workload throughputs during testing and thereby simulate larger deployments. The architecture presented here should scale to many more directors and backend Apache servers as your resources permit, but we haven't tried anything larger ourselves. Figure 1 shows our implementation using the Linux Virtual Server and the linux-ha.org components.

Howto Setup Linux Apache Web Server Cluster with Linux Virtual Server and Heartbeat

However article failed to mention few things such as redundant networking, a cluster file system / shared storage and other stuff. Nevertheless tutorial is a good start for new Linux admin.

=> Set up a Web server cluster in 5 easy steps

If you try to mount an ext3 Linux filesystem on a SAN from multiple nodes at the same time you will be in serious deep trouble.

SAN based storage allows multiple nodes to connect to same devices at the same time. Ext3/2 are not cluster aware file system. They can lead to a disaster such as kernel panic, server hang, corruption etc.

You need to use something which supports:

  1. Useful in clusters for moderate scale out and shared SAN volumes
  2. Symmetrical Parallel Cluster File System, Journaled
  3. POSIX access controls

Both GFS (RedHat Global File System) and Lustre (a scalable, secure, robust, highly available cluster file system) can be used with SAN based storage allows multiple nodes to connect to same devices at the same time.

Many newbie get confused as Linux offers a number of file systems. This paper (Linux File System Primer) discusses these file systems, why there are so many, and which ones are the best to use for which workloads and data.