Introduction If you are looking for information to use free libraries to convert and resize video files within a Scala or Java project, you may probably have cross the road of an open source project called Xuggle .This library is written in Java but is using native code from ffmpeg (another open source project) for the many video and […]
It covers the main differences between ext3 and ext4 with a focus on filesystem consistency. This article was the initial motivation of this blog series, because many engineers are unaware that the standard option of ext4 (delalloc) is dangerous for their data! 4.1 Main differences Ext3 was available since 2001 with Linux Kernel 2.4.15 and […]
This blog article details how a brutal interruption of a write operation can corrupt a whole filesystem and how a journal provides a protection against such incomplete writes. 3.1 Consequences of uncomplete writes When you write a file, the underlying filesystem is actually doing two different kinds of write operations: metadata and data writes. For […]
This article aims to give a clear representation of the relation between filenames and inodes, to explain what is an inode and which differences exist between a hard link and a symbolic link. 2.1 Filename as Hardlink to Inode On ext3 and ext4 (and some other filesystems) a file is stored internally as an inode […]
It explains how files are split into blocks and how the filesystem acts as an abstraction layer between files (seen by applications) and blocks (physically written on disks). It also says why disks are called block devices. 1.1 Splitting Up Files Into Blocks A block device is a storage media, like a hard disk. You […]
This blog series aims to be a reference guideline by collecting useful knowledge and tutorials about Linux filesystems, mainly about ext3 and ext4. Because, as systems engineers/administrators, when we need to manually perform disk maintenance on a server, we know that a tiny mistake may have large consequences. “Trial-and-Error” is sometimes a good way to […]
Introduction Your Linux servers are running smoothly? Fine.Now if something incidentally gets wrong you need also to prepare an emergency plan.And even when everything is going fine, a backup that is directly stored on the same server can still be useful: for example when you need to see what was changed on a specific file, […]
Introduction Having a complete history of all typed commands can be very helpful in many scenarios: when several administrators work together on the same server and need to know what was done previously when someone need to redo an older sequence of commands or to understand an undocumented maintenance process for troubleshooting or forensic analysis, […]
Hardware clustering is frequently used in computer systems where high availability and scalability are needed. In horizontal clustering the same application software is typically installed on multiple identical nodes. For web applications load balancing software such as Cisco’s ‘Global Site Selector’ is used to direct client requests to nodes based on rules (fig 1). The […]